Effects of age and symptom status on silent ischemic lesions after carotid stenting with and without the use of distal filter devices

BACKGROUND AND PURPOSE: The routine use of distal filter devices during carotid angioplasty and stent placement (CAS) is controversial. The aim of this study was to analyze their effects on the incidence of new diffusion-weighted imaging (DWI) lesions as surrogate markers for stroke in important subgroups.materials and METHODS: DWI was performed immediately before and after CAS in 68 patients with and 175 without protection, and patients were further subdivided according to their age or symptom status.RESULTS: The proportion of patients with new ipsilateral DWI lesion(s) was significantly lower after protected versus unprotected CAS (52% versus 68%), as well as in symptomatic patients (56% versus 74%) or those at or younger than 75 years of age (46% versus 67%; all P < .05). Similarly, the total number of lesions was significantly lower after protected versus unprotected CAS (median, 1; interquartile range [IQR], 0–2; versus median, 1; IQR 0–4.75) and in symptomatic patients (median, 1; IQR, 0–3; versus median, 2; IQR, 0–6) or those at or younger than 75 years of age (median, 0; IQR, 0–2; versus median, 1; IQR, 0–4; all P < .05). In contrast, for asymptomatic patients (48% versus 52%; P = .8; median, 0; IQR, 0–2; versus median, 1; IQR, 0–2.5; P = .6) or those older than 75 years of age (73% versus 69%; P = .7; median, 1; IQR, 0–4; versus median, 1.5; IQR, 0–5.75; P = .6), the proportion of patients with new lesion(s) and the total number of these lesions were not significantly different between protected and unprotected CAS.CONCLUSIONS: The use of distal filter devices generally reduces the incidence of new DWI lesions; however, this beneficial effect might not necessarily pertain to older and asymptomatic patients.

Carotid endarterectomy (CEA) is currently the accepted standard of treatment for patients with symptomatic and some selected patients with a severe asymptomatic internal carotid artery stenosis.^1,2 In the past few years, however, carotid angioplasty and stent placement (CAS) has emerged as an alternative endovascular treatment strategy for these disorders. Although initial single-center case series and registries have reported acceptable periprocedural complication rates after CAS even in surgical high-risk patients,^3–6 recent randomized trials directly comparing CAS with CEA have produced conflicting results.^7–9 Compared with surgery, CAS potentially has the major disadvantage of producing more emboli to the brain,¹⁰ which has led to the development and widespread application of cerebral protection devices aimed at preventing the passage of embolic material into the cerebral vasculature. Although the concept of cerebral protection is generally appealing and has been corroborated by a meta-analysis of single-center studies and large registries,^6,11 the use of either balloon occlusion techniques or filter systems increases the duration, the technical complexity, as well as the costs of the intervention and is, thus, no panacea for CAS. Indeed, the periprocedural complication rates were comparable between those patients treated with and without cerebral protection in the recently published stent-protected angioplasty versus carotid endarterectomy in symptomatic patients (SPACE) trial.⁷ Moreover, the 30-day incidence of death and stroke was unacceptably high in the Endarterectomy Versus Angioplasty in Patients with Severe Symptomatic Carotid Stenosis Trial despite the use of cerebral protection devices during CAS.⁸ Although these results partially reflect a lack of experience of the interventional physicians in these trials,¹² it is also conceivable that only certain subgroups of patients actually profit from the use of these devices. In fact, it could be speculated that the potential impact of protection devices on outcome is pronounced in those patients who have been shown to have a high risk of embolic complications during unprotected CAS, such as older patients, and is negligible or even harmful in low-risk patients.^6,13 Because of the relatively small number of clinical events after CAS, it has become a major challenge to identify correlates of clinically silent events to define the role of cerebral protection devices on outcome overall, as well as in important subgroups. The use of diffusion-weighted imaging (DWI) to detect clinically silent emboli during CAS as surrogate markers for stroke could pave the way out of this dilemma.^14–16 In support of this notion, we demonstrated recently an overall positive effect of cerebral protection devices on the number of new DWI lesions after CAS, which were closely related to the clinical outcome.¹⁵ Using this prospective and updated CAS series, the aim of this study was to analyze the effects of cerebral protection devices on the incidence of new DWI lesions in 2 important subgroups, namely, younger and older patients, as well as those with a symptomatic or asymptomatic carotid stenosis.     

Incidental acute infarcts identified on diffusion-weighted images: a university hospital-based study

BACKGROUND AND PURPOSE: Pathogenesis of leukoaraiosis is incompletely understood and accumulation of small infarctions may be one of the possible sources of such white matter lesions. Thus, the purpose of this study was to identify the rate of incident infarction as depicted on diffusion-weighted images (DWIs) obtained from a general patient population.MATERIALS AND METHODS: During the 4-year study period, a total of 60 patients (36 men and 24 women) had an incidental DWI-defined infarction without overt clinical symptoms suggestive of a stroke or a transient ischemic attack. All of the MR images were obtained by using a similar protocol on 2 identical 1.5T whole-body scanners. The patient''s vascular risk factors, as well as the presence of white matter lesions (WMLs) on MR imaging and atheromatous changes on MR angiography, were assessed retrospectively. The incidental DWI-defined infarcts were also characterized in terms of their lateralization, lobe, and specific location.RESULTS: A total of 16,206 consecutive brain MR images were done during the study period; the overall incidence of incidental infarcts was 0.37%. Most of these patients with an incidental infarct had vascular risk factors and WMLs on MR images. Most of these patients (80%) had a single lesion on DWI. A total of 88 lesions were identified; most were located in the white matter of the supratentorial brain, primarily in the frontoparietal lobes. There were also lesions involving the brain stem (n = 2). The lesions involving cerebrum were more commonly located in the right side (right to left = 52:34).CONCLUSION: Small, DWI-defined acute brain infarctions can be found incidentally in an asymptomatic population; this finding may account, at least in part, for the pathogenesis of WMLs identified on MR imaging.

White matter lesions depicted on MR imaging have been a center of debate for many years. These white matter rarefactions were originally described on CT and termed “leukoaraiosis” by Hachinski et al.¹ Epidemiologic studies have shown that leukoaraiosis is correlated with age, hypertension (HT), and arteriosclerosis.^2-6 Other reported causative factors include cigarette smoking⁶ and glucose intolerance.⁵ These predisposing factors are also found in patients with lacunar infarcts; thus, it has been proposed that leukoaraiosis and symptomatic lacunar infarcts share a similar underlying vasculopathy, namely, subcortical occlusive small-vessel disease secondary to arteriolosclerosis.^7-9Population studies have noted that leukoaraiosis progresses over a period of years.^6,10 The mechanism by which these lesions increase over time remains unknown. It has also not been determined whether a new white matter lesion (WML) focus grows slowly over a period of months or whether it suddenly appears and evolves rapidly as an acute infarct. Previously proposed mechanisms include both insidious and acute processes.^11-17 For instance, one of the proposed insidious mechanisms is apoptosis induced by chronic ischemia.¹⁴ Microembolic events have been proposed as an acute pathogenetic process.^15,16 Other proposed etiologies, which could be either insidious or acute, include intermittent changes in cerebral perfusion pressure resulting in incomplete infarction¹⁷ and white matter damage by altered blood-brain barrier permeability.^11-13Whatever the mechanism, these lesions will be seen on diffusion-weighted imaging (DWI), if at least some of them occur due to an acute process. Given that DWI has a unique contrast property and a relatively short acquisition time, this imaging technique has been incorporated into many routine brain MR protocols, including, among others, protocols for strokes,^18-21 headaches, seizures, and tumors.^22-24Over the past few years, we have used DWI for our routine brain protocol assuming that incidental infarcts would be identified on DWI performed in a general patient population. Although relatively uncommon given the total number of MR examinations that were done, a number of patients with incidental acute or subacute infarcts were identified. These patients'' clinical and imaging data were retrospectively analyzed to elucidate the significance of our observations.     

Isolated cortical signal increase on MR imaging as a frequent lesion pattern in sporadic Creutzfeldt-Jakob disease

BACKGROUND AND PURPOSE: Hyperintense basal ganglia on MR imaging support the diagnosis of sporadic Creutzfeldt-Jakob disease (CJD). Our aim was to study the frequency of patients with sporadic CJD presenting with and without characteristic basal ganglia lesions on MR imaging and to examine the corresponding patient characteristics.MATERIALS AND METHODS: Fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted images (DWI) of 55 patients with CJD were assessed for signal-intensity increase (FLAIR) or restricted diffusion (DWI) in 7 cortex regions and the basal ganglia, thalamus, and cerebellum. Patient characteristics as well as electroencephalography, CSF, and codon 129 genotype of the prion protein gene (PRNP) were correlated with the most frequent MR imaging lesion patterns.RESULTS: Two major lesion patterns were identified by DWI: cortex and basal ganglia involvement (two thirds) and isolated cortex involvement (one third). In the latter patient group, the cortex involvement was widespread (at least 3 regions affected in 89% on DWI) and usually included the frontal and parietal lobes (78%). The length of the disease course was significantly prolonged (median, 12 versus 5 months). No significant differences were observed concerning electroencephalography and CSF findings and codon 129 genotype distributions. Of 4 patients with normal MR imaging findings, the CSF was positive for the 14-3-3 protein in 3.CONCLUSION: A high number of patients with CJD present without basal ganglia lesions on MR imaging. Isolated cortex involvement on DWI and FLAIR should lead to suggestion of CJD, even if the disease course is only slowly progressive. Additional 14-3-3 protein analysis in the CSF may support the CJD diagnosis.

Sporadic Creutzfeldt-Jakob disease (CJD) is a rare and fatal disease caused by the accumulation of abnormal/pathologic prion protein (PrP^Sc; Sc indicates scrapie) in the human brain. The classic disease type is characterized by rapidly progressive dementia, ataxia, abnormal muscle tone, and myoclonus. It leads to a state of akinetic mutism and death after a median disease duration of 6 months.¹ The definite CJD diagnosis relies on the finding of PrP^Sc in the brain tissue, together with astrocytic gliosis, nerve cell loss, and spongiform degeneration as the typical neuropathologic changes.^2,3During one''s lifetime, MR imaging hyperintensity of the basal ganglia on T2-weighted (T2WI), fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI) is increasingly used to support the CJD diagnosis, next to positive CSF (14-3-3 protein) and electroencephalography (EEG) findings of periodic sharp-wave complexes (PSWCs). Although the origin of the signal-intensity changes is still not fully understood, hyperintensity on T2WI and FLAIR has been thought to be caused by gliosis, whereas abnormalities on DWI are most likely derived from spongiform changes.^4–6 DWI was shown to be the most sensitive sequence in the detection of brain lesions, particularly in the neocortex.^7–10 Isolated cortex involvement was also found.^9,11Although abnormal MR imaging findings in CJD have been studied in detail with respect to their location, few attempts have been made to define the most frequently occurring patterns of hyperintensity in a spectrum of patients. Six disease phenotypes (MM1, MM2, MV1, MV2, VV1, and VV2) defined by the codon 129 genotype (MM, MV, VV) of the prion protein gene (PRNP) and pathologic isotype of the PrP^Sc type 1 or 2 have been recently described with distinctive neuropathologic features and various clinical and diagnostic findings.^1–3,12 On MR imaging, predominant cortical (VV1)¹³ or subcortical involvement (MV2 and VV2)^14,15 or no abnormalities (MM2)^16,17 were found in smaller case series.To date, to our knowledge, the overall distribution of MR imaging abnormalities has not been studied in a larger spectrum of patients with CJD, and it is unclear whether there are clinical correlates corresponding to specific MR imaging lesion patterns. The proportion of patients presenting without basal ganglia abnormalities is unknown.We defined the most frequent MR imaging lesion patterns and corresponding clinical characteristics in a CJD patient collective by using highly sensitive MR images, and we considered a possible influence of the codon 129 genotype of the PRNP. We particularly focused on patients lacking basal ganglia abnormalities on MR imaging and suggested criteria that might support the early CJD diagnosis in these patients.     

Optimal diffusion-weighted imaging protocol for lesion detection in transient global amnesia

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) can depict small punctate hyperintense lesions in the hippocampus in transient global amnesia (TGA). The purpose of this study was to find an optimal DWI protocol for lesion detection in TGA by investigating various imaging parameters and imaging timing after symptom onset.MATERIALS AND METHODS: Sixteen patients with TGA diagnosed during 14 months underwent DWI within 24 hours and again at follow-up 3 days after onset. Each DWI session included 4 different sequences using different b-values (seconds per square millimeter) and section thicknesses (millimeter): 1000/5, 1000/3, 2000/3, and 3000/3. The presence or absence of hyperintense lesions on the 8 DWIs was determined visually, and the number of lesions detected was compared.RESULTS: Thirteen of the 16 patients (81%) had either single or multiple punctate hyperintense lesions, totaling 24 lesions, and the remaining 3 patients had no lesions. All lesions detected were in the hippocampus except 1. The number of lesions detected on initial DWIs at a b-value/section thickness of 1000/5, 1000/3, 2000/3, and 3000/3 was 3, 9, 13, and 13, respectively, whereas that of follow-up DWIs was 17, 22, 24, and 24, respectively.CONCLUSION: On the basis of these preliminary results, the highest lesion detection was achieved for DWI with b = 2000/3 mm or b = 3000/3 mm at 3 days postonset. When no lesion is detected by DWI within 24 hours after onset, follow-up DWI is recommended several days later.

Transient global amnesia (TGA) is clinically defined as sudden onset anterograde amnesia with preserved alertness, attention, and personal identity, which occurs during a period of no more than 24 hours with no long-term sequelae.^1–3 The incidence of TGA has been reported to be 5–11 per 100,000 persons per annum.^2,4,5 The etiology and pathogenesis of TGA are uncertain, though several different causes are suggested, such as ischemia, migraine, epileptic seizure, venous congestion, and psychological disturbances.⁶Recent diffusion-weighted imaging (DWI) studies have indicated the presence of focal hyperintensities involving the hippocampus in TGA.^7–11 The lesions detected by DWI are small and punctate (1–3 mm) and located within the lateral portion of the hippocampus.^9,11,12 Since Strupp et al¹³ first detected hyperintense lesions in the hippocampus in TGA by using DWI, the frequency of lesions detected on DWI has been reported in a range of 0%–84%.^9,10,14,15 According to a recent study, this discrepancy in detection rates appears to be attributable to the different timing of imaging from the onset of symptoms.⁹ In this previous study, a detection rate of only 6% by DWI was achieved within several hours of symptom onset, but this increased up to 84% at 48 hours post-symptom onset.DWI parameters, such as b-value and section thickness, might also importantly influence the detection rate of the lesions. In particular, b-values higher than 1000 s/mm² might increase the ability of DWI to detect subtle diffusion restrictions caused by small lesions. Moreover, section thicknesses of <5 mm may also increase the detection rate of small punctate lesions by decreasing partial volume averaging effects. However, optimal DWI parameters for lesion detection have not been studied previously. The purpose of the present study was to find an optimal DWI protocol for lesion detection by investigating b-values, section thickness, and imaging timing after symptom onset.     

Comparison of echo-planar diffusion-weighted imaging and delayed postcontrast T1-weighted MR imaging for the detection of residual cholesteatoma

BACKGROUND AND PURPOSE: Echo-planar diffusion-weighted imaging (DWI) and delayed postcontrast T1-weighted MR imaging (DPI) have been proposed in previous studies to detect residual middle ear cholesteatomas, with varying results. We assessed and compared these 2 techniques in patients with canal wall-up tympanoplasty.MATERIALS AND METHODS: This was a prospective cohort study. Patients who underwent surgery for middle ear cholesteatoma had CT scanning 9 months after the surgery. If opacity was observed (64%) on CT scans, DWI and DPI were performed before second-look surgery. CT, MR imaging, and surgical data were available for 31 patients. Charts were reviewed independently by 3 blinded examiners. Interobserver agreement for MR imaging was calculated (Cohen κ). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for these techniques: 1) alone or in association, and 2) according to the residual cholesteatoma size measured during surgery.RESULTS: Interobserver agreement was better for DWI (κ = 0.81) than for DPI (κ = 0.51). Sensitivity, specificity, PPV, and NPV values were 60%, 72.73%, 80%, and 50%, respectively, with DWI; and 90%, 54.55%, 78.26%, and 75%, respectively, with DPI. With cholesteatomas >5 mm, the sensitivity and specificity of DWI reached 100% and 88%, respectively, with values for DPI reaching 100% and 80%, respectively. The association of both techniques only allowed improvements in the specificity for lesions >5 mm.CONCLUSIONS: Both techniques gave acceptable results for residual cholesteatoma detection. DWI is more specific but less sensitive than DPI. Their concurrent use may benefit patients by avoiding undue surgery.

Unlike recurrent cholesteatoma, developing from recurring retraction pockets or defects in the tympanic membrane reconstruction, residual cholesteatoma cannot be detected by a simple clinical examination. Several methods, such as eustachian tube endoscopy,^1-3 have been proposed to detect residual cholesteatomas. However, these techniques are not routinely performed and canal wall-up (CWU) tympanoplasties for middle ear cholesteatoma usually require second-look surgery to rule out the presence of residual cholesteatoma, observed in 6%–57% of patients in large series.^4,5 Any reliable noninvasive method of detecting residual cholesteatomas could allow the avoidance of second-look surgery in patients with no hearing loss after the first surgery.Imaging may prove useful in this respect. High-resolution CT displays a high negative predictive value (NPV)⁶ because of the lack of opacity in the middle ear cleft or because the mastoid cavity correlates well with the absence of a residual lesion. Nevertheless, CT does not allow a distinction between residual cholesteatoma and granulation or postoperative inflammatory or scar tissue.^3,7 However, MR imaging has been proposed to discriminate these tissues. T1- and T2-weighted sequences associated with diffusion-weighted imaging (DWI) or delayed postcontrast T1 sequences (DPI), though not early postcontrast T1 sequences, seem able to detect residual cholesteatoma among other types of tissue.^8-10 Results of sensitivity, specificity, positive predictive value (PPV), and NPV vary among previous studies.^8,11-15 One explanation for this discrepancy may be the different sizes of residual cholesteatomas studied in these series.In the present study, we aimed to compare echo-planar imaging (EPI) DWI and DPI for the detection of residual cholesteatoma after CWU surgery. Here we describe the results obtained by using both types of sequences in each patient, along with the size of the residual cholesteatoma as surgically verified in all patients.     

In vivo differentiation of aerobic brain abscesses and necrotic glioblastomas multiforme using proton MR spectroscopic imaging

BACKGROUND AND PURPOSE: Abscesses caused by aerobic bacteria (aerobic abscesses) can simulate intracranial glioblastomas multiforme (GBMs) in MR imaging appearance and single voxel (SV) proton MR spectroscopy of the central cavity. The purpose of our study was to determine whether MR spectroscopic imaging (SI) can be used to differentiate aerobic abscesses from GBMs. Our hypothesis was that metabolite levels of choline (Cho) are decreased in the ring-enhancing portion of abscesses compared with GBMs.MATERIALS AND METHODS: Fifteen patients with aerobic abscesses were studied on a 1.5T MR scanner using an SV method and an SI method. Proton MR spectra of 15 GBMs with similar conventional MR imaging appearances were used for comparison. The resonance peaks in the cavity, including lactate, cytosolic amino acids, acetate, succinate, and lipids, were analyzed by both SV MR spectroscopy and MRSI. In the contrast-enhancing rim of each lesion, peak areas of N-acetylaspartate (NAA), choline (Cho), lipid and lactate (LL), and creatine (Cr) were measured by MRSI. The peak areas of NAA-n, Cho-n, and Cr-n in the corresponding contralateral normal-appearing (-n) brain were also measured. Maximum Cho/Cr, Cho/NAA, LL/Cr-n, and Cho/Cho-n and minimum Cr/Cr-n and NAA/NAA-n ratios in abscesses and GBMs were compared using the Wilcoxon rank sum test. After receiver operating characteristic curve analysis, diagnostic accuracy was compared.RESULTS: Cytosolic amino acid peaks were found in the cavity in 7 of 15 patients with aerobic abscesses. Means and SDs of maximum Cho/Cr, Cho/NAA, LL/Cr-n, and Cho/Cho-n and minimum Cr/Cr-n and NAA/NAA-n ratios were 3.38 ± 1.09, 3.88 ± 2.13, 2.72 ± 1.45, 1.98 ± 0.53, 0.53 ± 0.16, and 0.44 ± 0.09, respectively, in the GBMs, and 1.77 ± 0.49, 1.48 ± 0.51, 2.11 ± 0.67, 0.81 ± 0.21, 0.48 ± 0.2, and 0.5 ± 0.15, respectively, in the abscesses. Significant differences were found in the maximum Cho/Cr (P = .001), Cho/NAA (P = .006), and Cho/Cho-n ratios (P < .001) between abscesses and GBMs. Diagnostic accuracy was higher by Cho/Cho-n ratio than Cho/Cr and Cho/NAA ratios (93.3% versus 86.7% and 76.7%).CONCLUSION: Metabolite ratios and maximum Cho/Cho-n, Cho/Cr, and Cho/NAA ratios of the contrast-enhancing rim were significantly different and useful in differentiating aerobic abscesses from GBMs by MRSI.

Brain abscess can be a lethal condition if appropriate treatment is delayed. Thus, early diagnosis of brain abscess is desired and is a challenge for clinicians and radiologists. Radiologically, a brain abscess in the capsule stage appears in CT and in MR imaging as an expansile, rim-enhancing mass surrounded by edema, which is similar in appearance to necrotic malignant tumors, especially glioblastoma multiforme (GBM).^1,2 Clinically, both brain abscesses and GBMs may cause nonspecific headaches in the absence of fever, focal neurologic deficits, epileptic seizures, and disturbances in higher-level cortical function. In addition, laboratory examination often shows normal white blood cell count.^1,2 Further reduction of mortality from brain abscesses requires more rapid, accurate, and safe diagnostic techniques. Application of diffusion-weighted imaging (DWI) in distinguishing between pyogenic brain abscesses and cystic or necrotic brain tumors has been reported to be useful in many publications.^3–8 The cystic or necrotic portion of tumors almost always has a low signal intensity on DWI and a higher apparent diffusion coefficient (ADC) value; however, some exceptions have been reported for necrotic brain tumors.^7–12 Hyperintensity with restricted diffusion is diagnostic, but not pathognomonic, for pyogenic abscess on DWI. However, exceptions of DWI studies and substantial variability in the ADCs have been reported for pyogenic abscesses.^8,12–16Single-voxel proton MR spectroscopy of the central cystic portion has been reported to allow the broad group of pyogenic abscesses to be distinguished from malignant gliomas.^17–22 Acetate, succinate, and amino acids have been identified in cerebral abscesses in humans and were used as bacterial marker metabolites for noninvasive diagnosis by MR spectroscopy.^17–22 Abscesses caused by anaerobic bacteria have been distinguished from those caused by aerobic bacteria based on metabolites detectable with MR spectroscopy (acetate and succinate).^21–23 However, spectral patterns recorded for the cystic or necrotic components of GBMs and abscesses caused by aerobic bacteria (aerobic abscesses) were similar by single-voxel MR spectroscopy.^18,21,24 Diagnosis based on such subjectively selected metabolites or metabolite ratios was not possible.²⁴At pathologic examination, the enhancing rim of GBMs represents infiltrating tumor cells,^25,26 and an increased Cho/Cr ratio was observed. Pathologically, the enhancing rim of a pyogenic abscess represents an inflammatory infiltrate composed of neutrophils and, later, macrophages and lymphocytes. Granulation tissue surrounds the area of inflammation and eventually develops into a fibrous capsule. This capsule, in turn, is surrounded by gliotic, edematous brain tissue. In the experimental setting, brain abscesses have been shown to have relatively high amounts of mature collagen and decreased neovascularity.^27,28 The Cho/Cr ratio of rim-enhancing lesion of abscesses would be presumed to be less than that of GBMs.Recent developments in MR spectroscopy have made it possible to obtain spectroscopic MR imaging with high spatial resolution and multiple spectra simultaneously from contiguous voxels.^29,30 To date, proton MR spectroscopic imaging has not been used to differentiate aerobic abscesses from GBMs. We aimed to test the feasibility of MR spectroscopic imaging to distinguish between aerobic abscesses and GBMs by the evaluation of the contrast-enhancing rim of the lesions. Our hypothesis was that metabolite levels of Cho are decreased in the rim-enhancing portion of aerobic abscesses relative to the Cho seen in the rim-enhancing portion of necrotic GBMs.     

MR imaging of familial Creutzfeldt-Jakob disease: a blinded and controlled study

BACKGROUND AND PURPOSE: The E200K mutation of the PRNP (prion protein) gene is the most common cause of familial Creutzfeldt-Jakob disease (fCJD), which has imaging and clinical features that are similar to the sporadic form. The purpose of this study was to conduct a controlled and blinded evaluation of the sensitivity and specificity of MR imaging in this unique population.MATERIALS AND METHODS: We compared the MR imaging characteristics of 15 early stage familial CJD patients (age, 60 ± 7 years) with a group of 22 healthy subjects from the same families (age, 61 ± 8 years). MR imaging included diffusion-weighted imaging (DWI), T2-weighted fast spin-echo imaging, and a fluid-attenuated inversion recovery (FLAIR) sequence. The scans were rated for abnormalities by an experienced neuroradiologist blind to diagnosis, group assignment, age, and sex.RESULTS: Thirteen of 15 fCJD subjects had abnormal MR imaging. FLAIR signal intensity abnormality in the caudate or putamen nuclei demonstrated a sensitivity of 87% and specificity of 91%. DWI abnormality in the caudate nucleus showed a sensitivity of 73% and a specificity of 100%. Abnormalities in the thalamus (6 patients), cingulate gyrus (6 patients), frontal lobes (4 patients), and occipital lobes (3 patients) were best detected with DWI. No signal intensity abnormalities were demonstrated in the cerebellum. T2-weighted and T1-weighted sequences were uninformative.CONCLUSIONS: FLAIR and DWI abnormalities in the caudate nucleus and putamen offer the best sensitivity and specificity for diagnosing fCJD. Our findings support recent recommendations that MR imaging should be added to the diagnostic evaluation of CJD.

Creutzfeldt-Jakob disease (CJD) is the most common human prion disease. It is a rare neurodegenerative disorder that is progressive and invariably fatal, with nearly 90% of patients dying within 1 year of diagnosis.¹ CJD occurs in approximately 1 person per 1 million people per year worldwide.¹ The most common form is sporadic CJD (sCJD), which occurs randomly without a known risk factor and accounts for 85%-90% of cases. Familial or hereditary CJD (fCJD), seen in 5%-10% of cases, is caused by mutations in the gene that controls formation of the normal prion protein on chromosome 20.¹ The most common pathogenic mutation is the E200K mutation. The risk of fCJD is transmitted in an autosomal dominant inheritance pattern, with nearly 100% penetrance.²The imaging findings in sCJD typically consist of cortical atrophy and hyperintensities in the basal ganglia, thalamus, and cortex on fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI).^3–13 fCJD has imaging findings and neuropathology that are, in general, similar to the most common forms of sCJD; however, most imaging studies on fCJD consist primarily of case reports or studies focused on sCJD that combine a few fCJD patients into a single CJD patient sample.^8,14–22 fCJD studies are limited not only by small sample sizes but also by nonstandardized imaging protocols and clinical and pathophysiologic heterogeneity. The complex interactions with disease duration and cognitive and neurologic severity have also made it difficult to interpret studies, especially because the sample sizes are small.²³To address the difficulties of clinical research in this area, we initiated a study of fCJD occurring among Libyan Jews living in Israel that is caused by familial transmission of the E200K mutation.^24–26 In a preliminary report, it was demonstrated that 4 patients with fCJD due to the E200K mutation had gray matter atrophy and decreased apparent diffusion coefficient (ADC) in the basal ganglia. Signal intensity hyperintensities were seen in the basal ganglia and thalamus with FLAIR and DWI.²⁷ The sample size in that study was insufficient to calculate sensitivity and specificity. Here we describe a rigorously blinded and controlled evaluation of MR imaging findings in a larger number of fCJD patients.     

High b-value diffusion tensor imaging of the neonatal brain at 3T

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging studies of the adult brain have shown that contrast between lesions and normal tissue is increased at high b-values. We designed a prospective study to test the hypothesis that diffusion tensor imaging (DTI) obtained at high b-values increases image contrast and lesion conspicuity in the neonatal brain.MATERIALS AND METHODS: We studied 17 neonates, median (range) age of 10 (2–96) days, who were undergoing MR imaging for clinical indications. DTI was performed on a Philips 3T Intera system with b-values of 350, 700, 1500, and 3000 s/mm². Image contrast and lesion conspicuity at each b-value were visually assessed. In addition, regions of interest were positioned in the central white matter at the level of the centrum semiovale, frontal and occipital white matter, splenium of the corpus callosum, posterior limb of the internal capsule, and the thalamus. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values for these regions were calculated.RESULTS: Isotropic diffusion image contrast and lesion-to-normal-tissue contrast increased with increasing b-value. ADC values decreased with increasing b-value in all regions studied; however, there was no change in FA with increasing b-value.CONCLUSIONS: Diffusion image contrast increased at high b-values may be useful in identifying lesions in the neonatal brain.

Diffusion-weighted MR imaging is increasingly being used to investigate neonatal cerebral pathologic lesions. Previous studies have shown that diffusion-weighted imaging (DWI) is able to demonstrate lesions that are not always discernible on conventional MR imaging, and the usefulness of this imaging technique to assess infarction^1-3 and metabolic disorders^4,5 in the neonatal brain is established. In addition to the qualitative assessment of injury, diffusion tensor imaging (DTI) provides directionally invariant measurements of mean diffusivity and diffusion anisotropy. These objective measurements provide information regarding water molecular mobility, which reflect tissue microstructure and thereby provide insight into mechanisms of brain development and disease processes.Diffusion-weighted MR imaging with b-values of more than 2000 s/mm² has been performed in animal studies,^6,7 in the adult brain,^8-14 and in infants.^8,15 These studies suggest that diffusion contrast characteristics are altered at higher b-values. In addition, adult studies of cerebral infarction¹³ and white matter disease¹⁴ have shown increased lesion conspicuity at higher b-values, and so it is possible that high b-value DTI in neonates may also improve lesion conspicuity.To our knowledge, the only studies investigating the effects of high b-value diffusion imaging in the neonatal brain were done on infants whose results on conventional MR imaging was considered normal and did not examine the full diffusion tensor.^8,15 In this prospective study, we tested the hypothesis that diffusion imaging at high b-values enhances contrast between lesions and normal tissue in neonates and thereby increases lesion conspicuity. Furthermore, we acquired diffusion data in 6 noncollinear directions of sensitization, enabling us to examine the effects of high b-values on diffusion anisotropy.The aims of this study were 1) to assess isotropic DWI contrast and lesion conspicuity at b-values between 350 and 3000s/mm² and 2) to assess whether apparent diffusion coefficient (ADC) or fractional anisotropy (FA) in the neonatal brain change with increasing b-value.     

New ischemic brain lesions on diffusion-weighted MRI after carotid artery stenting with filter protection: frequency and relationship with plaque morphology

BACKGROUND AND PURPOSE:CAS carries an inherent risk of distal cerebral embolization, precipitating new brain ischemic lesions and neurologic symptoms. Our purpose was to evaluate the frequency of new ischemic lesions found on DWI after protected CAS placement and to determine its association with plaque morphology.MATERIALS AND METHODS:Fifty patients (mean age 65.13 ± 7.08 years) with moderate and severe internal carotid artery stenosis underwent CAS with distal filter protection. Fibrolipid and fibrocalcified plaque morphology was determined by sonography according to the relative contribution of echogenic and echolucent material, and by multisection CT using plaque attenuation. There were 46.81% of patients with fibrolipid and 53.19% with fibrocalcified plaques. DWI was performed before and 24 hours after CAS.RESULTS:Seven (14.89%) patients showed new lesions. Four (8.51%) had 6 new lesions inside the treated vascular territory. Three had a single lesion and 1 patient had 3 lesions (mean: 1.5 ± 1). Most lesions (66.66%) were subcortical, with a mean diameter of 9 mm (range 5–15 mm). All lesions occurred in the area supplied by the middle cerebral artery and were clinically silent. A significant relationship was found between plaque morphology and the appearance of new lesions. Patients with fibrolipid plaques had a significantly higher number of new lesions compared with patients with fibrocalcified plaques (P = .041). The absolute risk of new lesions in the fibrolipid group was 18.18%.CONCLUSIONS:New ischemic lesions were observed in the treated vascular territory in 8.51% of patients. The appearance of new ischemic lesions was significantly related to the plaque morphology. Fibrolipid plaques were associated with higher numbers of new lesions.

CAS carries an inherent risk of distal cerebral embolization, precipitating new brain ischemic lesions and neurologic symptoms.^1–4 This has led to the development and widespread application of cerebral protection devices.^5,6 The most widely used devices are those based on distal filter placement that capture emboli dislodged from plaque; however, their application may result in additional complications.^7–12Several reviews have reported contradictory data concerning the rate of stroke and ischemia after protected versus unprotected stent placement.^3,13–15 The frequency of new ischemic lesions after CAS may be associated with numerous factors, such as clinical status, vascular anatomy, plaque morphology, and complexity. Therefore, the need to identify patients at risk for embolic events has become increasingly important. The morphologic characteristics of atherosclerotic carotid plaques may be useful in heralding embolic potential in the carotid arteries. Several authors have reported that plaques in the carotid arteries that are associated with large lipid pools or soft extracellular lipid are more prone to rupture and production of emboli.¹⁶ DWI is the most sensitive tool for the detection of neurologically silent or asymptomatic infarcts at a very early stage.^17–19The aim of this study was to determine the frequency of new ischemic DWI lesions in patients with moderate and severe ICA stenosis after protected CAS using a filter device, and to determine its potential association with plaque morphology.     

Contribution of diffusion-weighted imaging in the evaluation of diffuse white matter ischemic lesions in fetuses: correlations with fetopathologic findings

BACKGROUND AND PURPOSE: The sensitivity of fetal MR imaging is poor with regard to the evaluation of diffuse ischemic white matter (WM) abnormalities. Our purpose was to evaluate the contribution of diffusion-weighted imaging (DWI) in the analysis of microstructural changes in WM and to correlate neuroimaging with neurofetopathologic findings.MATERIALS AND METHODS: We included fetuses with MR imaging, DWI, and a fetopathologic examination. In a region of interest defined by MR imaging, where T1 and T2 intensities were abnormal, the apparent diffusion coefficient (ADC) was measured and immunohistochemical analysis was performed. In fetuses with no WM abnormality in signal intensity, region of interest was defined at random. Histologic reading was performed with a complete blinding of the MR imaging results and ADC values. Three degrees of histologic appearance were defined with regard to vasogenic edema, astrogliosis, microgliosis, neuronal and oligodendrocytic abnormalities, and proliferation or congestion of vessels and were compared with a χ² test in groups A (normal ADC) and B (increased ADC) fetuses.RESULTS: We included 12 fetuses in group A and 9 in group B, ranging from 29 to 38 weeks of gestation. All group B fetuses and 1 group A fetus demonstrated WM abnormalities in signal intensity. WM edema and astrogliosis were more common in group B than in group A (7/9 vs 2/12 and 8/9 vs 4/12, respectively). No significant difference was observed between both groups with regard to the other parameters.CONCLUSION: This study showed a strong correlation between increased ADCs and 1) WM abnormalities in signal intensity on MR imaging, and 2) vasogenic edema with astrogliosis of the cerebral parenchyma.

The contribution of fetal MR imaging in the evaluation of cerebral ischemic lesions has already been evaluated.¹ MR imaging with the use of T2, T1, and T2*-weighted sequences has proved a valuable tool during the third trimester in the detection of small focal parenchymal lesions (such as cavitations and calcified leukomalacia) and ischemic lesions involving the cortex (4-layered polymicrogyria and laminar necrosis).^1,2 Conversely, the sensitivity of MR imaging was poor in the evaluation of diffuse ischemic white matter (WM) abnormalities.¹ However, the detection of such lesions, before the establishment of irreversible damage, is challenging in at-risk situations.Injury to the WM gives rise to neuronal hypoxia and, subsequently, to neuronal death, which results in disruption of the cell membrane and the release of some neurotransmitters such as glutamate. The latter has been demonstrated to have a cytotoxic effect on neurons.³ From this step begins microglial and astrogliosis responses. Microglial cells produce proinflammatory cytokines and reactive oxygen and nitrogen species that contribute to the strength of this deleterious effect.⁴ Astrocytes are recruited to repair the injured tissue and to reduce the effect of glutamate, resulting in a cellular swelling that corresponds to cytotoxic edema. A secondary vasogenic edema appears, caused principally by lysis of the astrocytic cell membrane and an opening in the blood-brain barrier, which induces an increase of the amount of water in the extracellular space.⁵ This vasogenic edema is present 1 week after the insult.⁶The purpose of this study was to evaluate the contribution of diffusion-weighted imaging (DWI) in the evaluation of diffuse ischemic WM changes in fetuses, by correlating DWI and MR imaging with neurofetopathologic findings obtained by standard histologic and immunohistochemical analyses of the main cellular populations of the brain.     

Diffuse pachymeningeal hyperintensity and subdural effusion/hematoma detected by fluid-attenuated inversion recovery MR imaging in patients with spontaneous intracranial hypotension

BACKGROUND AND PURPOSE: Fluid-attenuated inversion recovery (FLAIR) MR imaging has advantages to detect meningeal lesions. FLAIR MR imaging was used to detect pachymeningeal thickening and thin bilateral subdural effusion/hematomas in patients with spontaneous intracranial hypotension (SIH).MATERIALS AND METHODS: Eight patients were treated under clinical diagnoses of SIH. Chronologic MR imaging studies, including the FLAIR sequence, were retrospectively reviewed.RESULTS: Initial MR imaging showed diffuse pachymeningeal thickening as isointense in 6 cases, hypoisointense in 1 case, and isohyperintense in 1 case on the T1-weighted MR images, and hyperintense in all cases on both T2-weighted and FLAIR MR images. Dural (pachymeningeal) hyperintensity on FLAIR MR imaging had the highest contrast to CSF, and was observed as linear in all patients, usually located in the supratentorial convexity and also parallel to the falx, the dura of the posterior fossa convexity, and the tentorium, and improved after treatment. These characteristics of diffuse pachymeningeal hyperintensity on FLAIR MR imaging were similar to diffuse pachymeningeal enhancement (DPME) on T1-weighted imaging with gadolinium. Initial FLAIR imaging clearly showed subdural effusion/hematomas in 6 of 8 patients. The thickness of subdural effusion/hematomas sometimes increased transiently after successful treatment and resolution of clinical symptoms.CONCLUSION: Diffuse pachymeningeal hyperintensity on FLAIR MR imaging is a similar sign to DPME for the diagnosis of SIH but does not require injection of contrast medium. FLAIR is useful sequence for the detection of subdural effusion/hematomas in patients with SIH.

Spontaneous intracranial hypotension (SIH) syndrome is characterized by low CSF pressure and positional headache caused by leakage of spinal CSF.^1,2 MR imaging has revolutionized the identification, diagnosis, management, and understanding of SIH. The characteristic MR signs of SIH include diffuse pachymeningeal (dura mater) enhancement (DPME), bilateral subdural effusion/hematomas, downward displacement of the brain, enlargement of the pituitary gland, prominence of the spinal epidural venous plexus, engorgement of cerebral venous sinuses (“venous distension sign,” etc),³ venous sinus thrombosis,⁴ and isolated cortical vein thrombosis.⁵ DPME after gadolinium administration may be the most common and indicative sign^1,2 and forms the basis of the proposed “syndrome of orthostatic headache and diffuse pachymeningeal gadolinium enhancement.”⁶The cause of DPME remains unclear. Histologic examination of meningeal biopsy specimens consistently demonstrates a thin layer of fibroblasts as well as small, thin-walled, dilated blood vessels without evidence of inflammation on the subdural surface, the so-called dural border cell layer.⁷ These findings strongly suggest that dural venous dilation following the Monro-Kellie rule is the most likely explanation of DPME associated with SIH, which states that decreased CSF volume caused by CSF leakage requires volume compensation resulting in meningeal venous hyperemia and subsequent pachymeningeal enhancement.⁸ However, previous studies did not include detailed neuroradiologic evaluations of the pachymeninges in patients with SIH without artificial contrast materials to evaluate the transient and functional changes of the dura mater.⁹Bilateral subdural effusion/hematomas are also classic intracranial signs in the diagnosis of SIH, which again may be explained by the Monro-Kellie rule.^1,6,8 The incidence of subdural effusion/hematomas associated with SIH is 10% to 50% with use of conventional neuroradiologic techniques.^10,11 Subdural effusion/hematomas associated with SIH tend to be thin (typically 2–7 mm), do not cause appreciable mass effect, occur typically over the convexities of the brain, and appear as variable MR signal intensities depending on the fluid protein concentration or presence of blood.¹The fluid-attenuated inversion recovery (FLAIR) pulse sequence cancels the signal intensity from CSF and causes heavy T2 weighting because of the very long TE, resulting in excellent definition of anatomic detail, such as brain surface sulci, and high lesion contrast in areas close to the CSF.¹² This method is commonly used to detect meningeal lesions such as subarachnoid hemorrhage and meningitis.^13–15 Therefore, FLAIR MR imaging may be the optimum sequence to evaluate the thickened dura associated with SIH and to detect the very thin subdural effusion/hematomas located close to the subarachnoid CSF space.Our study used FLAIR MR imaging to examine the thickened dura and subdural effusion/hematomas in patients with SIH.     

Role of apparent diffusion coefficient values in differentiation between malignant and benign solitary thyroid nodules

BACKGROUND AND PURPOSE: Accurate imaging characterization of a solitary thyroid nodule has been clearly problematic. The purpose of this study was to evaluate the role of the apparent diffusion coefficient (ADC) values in the differentiation between malignant and benign solitary thyroid nodules.MATERIALS AND METHODS: A prospective study was conducted in 67 consecutive patients with solitary thyroid nodules who underwent diffusion MR imaging of the thyroid gland. Diffusion-weighted MR images were acquired with b factors of 0, 250, and 500 s/mm² by using single-shot echo-planar imaging. ADC maps were reconstructed. The ADC values of the solitary thyroid nodules were calculated and correlated with the results of histopathologic examination. Statistical analysis was performed.RESULTS: The mean ADC value of malignant solitary thyroid nodules was 0.73 ± 0.19 × 10⁻³ mm²/s and of benign nodules was 1.8 ± 0.27 × 10⁻³ mm²/s. The mean ADC values of malignant nodules were significantly lower than those of benign ones (P = .0001). There were no significant differences between the mean ADC values of various malignant thyroid nodules, but there were significant differences between the subtypes of benign thyroid nodules (P = .0001). An ADC value of 0.98 × 10⁻³ mm²/s was proved as a cutoff value differentiating between benign and malignant nodules, with 97.5%, 91.7%, and 98.9% sensitivity, specificity, and accuracy, respectively.CONCLUSION: The ADC value is a new promising noninvasive imaging approach used for differentiating malignant from benign solitary thyroid nodules.

Nodular thyroid is commonly detected on palpation in 4%–7% of the population,^1,2 on sonographic examination in 10%–40%, and by pathologic examination at autopsy in 50%.^3,4 In contrast, compared with the high prevalence of nodular thyroid disease, thyroid cancer is rare. The challenge of imaging thyroid nodules is to reassure most patients who have benign disease and to diagnose the minority of patients who will prove to have a malignancy.^5,6Ultrasonography has been used in the assessment of the thyroid nodules as a primary imaging technique.^2,7,8 Currently, there is no single sonographic criterion that can reliably distinguish benign from malignant thyroid nodules.^4,9 The results of predicting thyroid cancer with color Doppler sonography are controversial, with some reporting that Doppler sonography is helpful and others reporting that it did not improve diagnostic accuracy.^4,5,10,11 The hazards of radiation exposure are unavoidable in nuclear scintigraphy,² and not all functioning nodules on scintigraphy are benign.^6,9 The risk of cancer in a cold nodule is 4 times more common than in a hot nodule.^3,6 Fine-needle aspiration biopsy (FNAB) with cytologic evaluation is commonly used, but it is inconclusive in 15%–20% of patients, in addition to the possible, but less likely, associated hemorrhage.^2,4 The incidence of cancer in patients with thyroid nodules selected for FNAB is approximately 9.2%–13%.⁵ FNAB is considered an effective method for differentiating between benign and malignant thyroid nodules.^4,7,12–14Routine T1- and T2-weighted MR imaging has a limited role in the evaluation of thyroid nodules. It cannot distinguish benign from malignant nodules or assess the functional status of thyroid nodules.^12–15 Diffusion-weighted MR imaging has been used to characterize head and neck tumors, in which there are significant differences in the apparent diffusion coefficient (ADC) values of malignant tumors and benign lesions.^16–19 Tezuka et al,²⁰ in their study using diffusion-weighted MR imaging to assess the thyroid function, reported that the ADC values of patients with Grave''s disease exceeded those of patients with subacute thyroiditis, with a sensitivity and specificity of 75% and 80%, respectively, in differentiating between both disease entities. They concluded that diffusion-weighted MR imaging could be clinically important in evaluating the thyroid function. To our knowledge, there have been no articles about diffusion-weighted MR imaging evaluating thyroid nodules.The aim of our study was to evaluate the role of ADC values in differentiating between malignant and benign solitary thyroid nodules.     

Sinonasal organized hematoma: CT and MR imaging findings

BACKGROUND AND PURPOSE: Sinonasal organized hematoma (OH) is an uncommon, nonneoplastic benign condition that can be locally aggressive. The purpose of this work was to characterize the CT and MR imaging findings of sinonasal OH.MATERIALS AND METHODS: CT (n = 11) and MR (n = 10) images of 12 patients (9 men and 3 women; mean age, 41 years; range, 12–76 years) with pathologically proved sinonasal OH were retrospectively reviewed. Particular attention was put on the location, shape, size, extent, internal architecture, and enhancement pattern of the lesion and associated sinus wall change.RESULTS: The lesions were seen as an expansile (n = 9) or nonexpansile (n = 3) mass, ranging in size from 2.2 to 6.0 cm (mean, 4.2 cm), primarily involving the maxillary sinus (n = 11) or nasal cavity (n = 1) unilaterally. The ipsilateral nasal cavity was also involved in 9 of 11 maxillary sinus lesions. Smooth sinus wall erosion other than the medial maxillary sinus wall was noted in 8 lesions. The internal architecture was best displayed on T2-weighted MR images on which all of the lesions were seen as a mixture of marked heterogeneous hypointensity and isointensity, surrounded by a hypointense peripheral rim, reflecting histologic heterogeneity of the lesion composed of hemorrhage, fibrosis, and neovascularization. Marked irregular nodular, papillary, or frondlike enhancement at the areas of neovascularization was also a typical finding seen in all of the lesions.CONCLUSION: An expansile soft tissue mass, smooth sinus wall erosion, marked heterogeneous signal intensity with a hypointense peripheral rim on T2-weighted MR images, and marked irregular nodular, papillary, or frondlike enhancement are characteristic CT and MR imaging findings of sinonasal OH.

Sinonasal organized hematoma (OH) is an uncommon, nonneoplastic benign condition that can be locally aggressive. Without careful evaluation of all of the imaging features, this may be mistaken for a malignant lesion both clinically and radiologically. It most commonly affects the maxillary sinus and can result from various causes of hemorrhage with chronic hematoma formation, followed by the process of organization through fibrosis and neovascularization.^1,2 Since the first report by Ozhan et al³ in a patient with von Willebrand disease, only fewer than 40 cases have been reported in the English literature under various names, including pseudotumor,^3,4 hematoma,⁵ organized or organizing hematoma,^1,2,6–8 and hematoma-like mass of the maxillary sinus.⁹Correct preoperative diagnosis of sinonasal OH is important to avoid unnecessary extensive surgery, because this condition is curative with a simple, conservative surgical approach and rarely recurs. Although there have been a few reports on the CT findings of sinonasal OH,^1–3,5–9 which are reported to be rather nonspecific, to our knowledge, the MR imaging features have not systematically been analyzed previously. Only 2 studies had briefly mentioned the MR imaging features.^8,9 Yagisawa et al⁹ reported that masses were well demarcated from the surrounding structures and heterogeneous in signal intensity on both T1- and T2-weighted MR images. Song et al⁸ reported that the lesions appeared as isosignal intensity with a margin that had a slightly higher signal intensity on T1-weighted images and a mosaic of various signal intensities and a low signal intensity rim on T2-weighted images. The purpose of this study was to report the CT and MR imaging findings, which are believed to be characteristic for sinonasal OH.     

Characterization of carotid atherosclerosis and detection of soft plaque with use of black-blood MR imaging

BACKGROUND AND PURPOSE: In the treatment of carotid atherosclerosis, the rate of stenosis and characteristics of plaque should be assessed to diagnose vulnerable plaques that increase the risk for cerebral infarction. We performed carotid black-blood (BB) MR imaging to diagnose plaque components and assess plaque hardness based on MR signals.MATERIALS AND METHODS: Three images of BB-MR imaging per plaque were obtained from 70 consecutive patients who underwent carotid endarterectomy (CEA) to generate T1- and T2-weighted images. To evaluate the relative signal intensity (rSI) of plaque components and the relationship between histologic findings and symptoms, we prepared sections at 2-mm intervals from 34 intact plaques. We then calculated the relative overall signal intensity (roSI) of 70 plaques to assess the relationship between MR signal intensity and plaque hardness and symptoms.RESULTS: The characteristics of rSI values on T1- and T2-weighted images of fibrous cap (FC), fibrosis, calcification, myxomatous tissue, lipid core (LC) with intraplaque hemorrhage (IPH), and LC without IPH differed. Symptomatic plaques were associated with FC disruption (P < .001) and LC with IPH (P < .05). The roSI on T1-weighted images was significantly higher for soft than nonsoft plaques. When the roSI cutoff value was set at 1.25 (mean of the roSI), soft plaques were diagnosed with 79.4% sensitivity and 84.4% specificity. The roSI was also significantly higher for symptomatic than for asymptomatic plaques. Soft and nonsoft plaques as well as symptomatic and asymptomatic plaques did not significantly differ on T2-weighted images.CONCLUSION: BB-MR imaging can diagnose plaque components and predict plaque hardness. This procedure provides useful information for planning therapeutic strategies of carotid atherosclerosis.

Carotid atherosclerosis accounts for a large proportion of the causes of cerebral infarction, and accurate diagnostic imaging of carotid stenosis is useful for clarification of the pathogenesis of cerebral infarction and planning of therapy. In the diagnostic imaging of carotid arterial lesions, luminography such as conventional angiography is generally performed to determine the rate of stenosis, and in randomized studies documenting the value of carotid endarterectomy (CEA) in the treatment of carotid atherosclerosis, therapeutic guidelines have been based on stenosis rate.^1–3 Recent studies have also shown the critical importance of diagnosing vulnerable plaques, which are associated with a higher risk for cerebral infarction, by imaging the carotid artery wall itself and determining plaque characteristics.^4,5 Therefore, less invasive and more accurate diagnostic modalities such as carotid ultrasonography (US) for plaque evaluation have considerable importance in the management of patients with carotid atherosclerosis. Carotid US has been widely applied to characterize atherosclerotic plaque, and the content of soft plaque (lipid and hemorrhage) is presently associated with echolucency.^6,7 Furthermore, accumulating evidence indicates that echolucent plaques represent biologically more active disease and are associated with the risk for future stroke.^8,9 In addition, although carotid artery stent placement (CAS) is becoming an increasingly popular alternative to CEA in the treatment of carotid stenosis, several reports have shown that soft plaques are associated with a high incidence of ischemic complication during CAS.^10–12 Therefore, accurate diagnosis of carotid soft plaque seems to be of paramount clinical importance. However, carotid US has some limitations because it is difficult to obtain full images on patients who have a short neck, high carotid bifurcation, or highly calcified plaques.¹³The chemical composition and physical properties of tissues can be determined by MR imaging, which indicates that this diagnostic technique should be useful in plaque characterization. Along with recent advances in imaging devices and techniques, many studies have documented the usefulness of high-resolution MR imaging in the diagnosis of plaque.^14–21 In addition to sorting plaque composition on the basis of MR signal intensity, if soft plaque can be differentiated from nonsoft plaque by overall plaque MR signal intensity, MR imaging will be a simple, objective, and useful method to diagnose carotid atherosclerosis. To our knowledge, however, few studies have closely assessed the MR imaging signals of plaque components by comparing CEA specimens with carotid MR imaging in vivo,²² and the findings on MR imaging of carotid soft plaque have not been described.Our study investigates the benefit of carotid black-blood (BB) MR imaging by evaluating the MR signal intensity of the components of carotid plaque and by detecting soft plaque on the basis of overall plaque MR signal intensity.     

A T1 hyperintense perilesional signal aids in the differentiation of a cavernous angioma from other hemorrhagic masses

BACKGROUND AND PURPOSE: A cavernous angioma is a developmental vascular malformation with a high risk of hemorrhage. The purpose of this work was to retrospectively determine whether an MR sign of T1 hyperintense perilesional signal intensity is useful for the differentiation of cavernous angioma from other hemorrhagic cerebral masses.MATERIALS AND METHODS: The institutional review board approved this study. We retrospectively evaluated the MR images of 72 patients with acute or subacute cerebral hemorrhagic lesions with perilesional edema (29 cavernous angiomas, 13 glioblastomas, 1 oligodendroglioma, 16 metastatic tumors, and 13 intracerebral hemorrhages) for the presence of T1 hyperintense perilesional signal intensity. In addition, T1 signal intensities of a perilesional edema were quantitatively analyzed. In cavernous angiomas, volumes of hemorrhagic lesions and perilesional edemas, lesion locations, presence of contrast enhancement, and time intervals between symptom onset and MR imaging were also assessed. Data were analyzed using unpaired t test or Fisher exact test.RESULTS: T1 hyperintense perilesional signal intensity sign was found in 18 (62.1%) of 29 cavernous angiomas, in 1 (6.3%) of 16 metastases, and in 0 primary brain tumors or intracerebral hemorrhages. Sensitivity, specificity, and positive predictive value of this sign for cavernous angioma were 62%, 98%, and 95%, respectively. The perilesional T1 hyperintensity was significantly higher in cavernous angiomas (P = .045) than in normal white matter. Perilesional edema volumes were larger in cavernous angiomas with the MR sign than in cavernous angiomas without the sign (P = .009).CONCLUSION: When the MR sign of T1 hyperintense perilesional signal intensity is present, there is a high probability of cavernous angioma being present in the brain, and this MR sign may be helpful for differentiating cavernous angioma from hemorrhagic tumors and intracerebral hemorrhages.

A cavernous angioma, also known as a cavernous malformation or cavernoma, is a developmental vascular malformation that is typically a discrete multilobulated, berrylike lesion containing hemorrhage in various stages of evolution. Hemorrhage is a common complication of a cavernous angioma and is the cause of the first presentation in 30% of cases.^1,2 The reported annual risk of hemorrhage in a cavernous angioma varies widely (1%–6.8%).^3–5MR imaging is the most important diagnostic technique for the detection of cavernous angiomas and frequently produces highly characteristic images. Typically, cavernous angiomas show a mixed signal intensity core, a reticulated “popcorn ball” appearance, and a “T2 blooming sign,” which is due to a low signal intensity hemosiderin rim that completely surrounds the lesion.^6,7 Susceptibility-weighted imaging, such as a T2* gradient-echo image, is more useful for the detection of the hemosiderin deposit and the diagnosis of a cavernous angioma. The typical MR signs of “popcorn ball” appearance and “T2 blooming sign” on T2-weighted images have been reported to be found in approximately 50%–67% of cavernous angiomas.^2,8Based on these MR findings, although diagnosis is usually straightforward in typical cases of a cavernous angioma, lesions with unusual MR features may be misdiagnosed as primary or metastatic brain tumors.^9–18 The atypical MR features of cavernous angiomas include variable or strong enhancement,^2,9,10,19 a large perilesional vasogenic edema and mass effect,^2,10,19,20 the cystic form of a cavernous angioma,^9,20,21 and the manifestations of a recent hematoma.^22,23 Cavernous angiomas that present with recent hemorrhage and with a surrounding edema may mimic a primary or secondary brain tumor with hemorrhage; these lesions may be frequently underestimated as a sole hematoma.Recently, we encountered some cases that showed T1 hyperintensity in a perilesional edema around the acute or subacute hemorrhagic masses. As far as we know, the MR feature of T1 hyperintensity in a perilesional edema around a hemorrhagic mass has not yet been documented. The aim of this study was to determine in a retrospective study whether the MR sign of a T1 hyperintense perilesional signal intensity is useful for differentiating a cavernous angioma from other hemorrhagic cerebral masses.     

Extent of microstructural white matter injury in postconcussive syndrome correlates with impaired cognitive reaction time: a 3T diffusion tensor imaging study of mild traumatic brain injury

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) may be a useful index of microstructural changes implicated in diffuse axonal injury (DAI) linked to persistent postconcussive symptoms, especially in mild traumatic brain injury (TBI), for which conventional MR imaging techniques may lack sensitivity. We hypothesized that for mild TBI, DTI measures of DAI would correlate with impairments in reaction time, whereas the number of focal lesions on conventional 3T MR imaging would not.MATERIALS AND METHODS: Thirty-four adult patients with mild TBI with persistent symptoms were assessed for DAI by quantifying traumatic microhemorrhages detected on a conventional set of T2*-weighted gradient-echo images and by DTI measures of fractional anisotropy (FA) within a set of a priori regions of interest. FA values 2.5 SDs below the region average, based on a group of 26 healthy control adults, were coded as exhibiting DAI.RESULTS: DTI measures revealed several predominant regions of damage including the anterior corona radiata (41% of the patients), uncinate fasciculus (29%), genu of the corpus callosum (21%), inferior longitudinal fasciculus (21%), and cingulum bundle (18%). The number of damaged white matter structures as quantified by DTI was significantly correlated with mean reaction time on a simple cognitive task (r = 0.49, P = .012). In contradistinction, the number of traumatic microhemorrhages was uncorrelated with reaction time (r = −0.08, P = .71).CONCLUSION: Microstructural white matter lesions detected by DTI correlate with persistent cognitive deficits in mild TBI, even in populations in which conventional measures do not. DTI measures may thus contribute additional diagnostic information related to DAI.

Traumatic brain injury (TBI) is the leading cause of death and disability in young people, with 1.4 million annually reported cases in the United States and an estimated 57 million people worldwide hospitalized with 1 or more TBIs.¹ Furthermore, approximately 80% of the hospital-reported patients with TBI are categorized as having mild TBI on the basis of a Glasgow Coma Scale score between 13 and 15. Although those patients with mild TBI with normal CT findings and no post-traumatic amnesia usually have complete resolution of post-traumatic symptoms within 1 month, approximately 30% of patients with mild TBI with posttraumatic amnesia have persistent posttraumatic symptoms, and a significant number at 1-year postinjury have decreased functional outcome.^2,3Structural imaging studies of acute TBI demonstrate that MR imaging is more sensitive than CT in the number of traumatic lesions visualized.⁴ However, the relationship between focal structural lesions detected by conventional MR imaging and long-term patient outcome is controversial.^3,5-7 Nevertheless, patients with TBI with posttraumatic symptoms often have cognitive impairment, and their cognitive function is a major predictor of poor outcome.^8-12 In particular, attention, working memory, cognitive manipulation of temporal information, and processing speed are vulnerable.^13,14 Sequelae of TBI cause significant disability, which compelled the National Institutes of Health (NIH) to declare mild TBI as a major public health problem.¹⁵Although conventional MR imaging techniques can readily visualize posttraumatic focal structural lesions, they fail to adequately detect diffuse axonal injury (DAI), the key mechanism of damage following TBI.¹⁶ DAI results from unequal rotational or acceleration/deceleration forces that cause multifocal lesions in white matter due to a shear-strain deformation.^17-19 DAI is primarily responsible for transient deficits in cognitive performance in domains such as processing speed, working memory, and attention.^20,21 More recent studies suggest that DAI causes persistent postconcussive symptoms in executive function and memory dysfunction.^8,22-25MR diffusion tensor imaging (DTI) may be used to better assess DAI. In DTI, the characteristics of water diffusion in the brain are used to assess microstructural integrity of white matter pathways.²⁶ In white matter, water diffuses more readily along the orientation of axonal fibers than across the fibers due to hindrance from structural elements such as the axolemma and the myelin sheath. One can calculate the apparent diffusion coefficient (ADC), which is a rotationally invariant measure of the magnitude of diffusion. The degree of directionality of diffusion is termed “anisotropy.” This is the variation in the eigenvalues of the diffusion tensor.²⁷ Fractional anisotropy (FA), a normalized measure of anisotropy, has been shown to be sensitive to microstructural changes in white matter integrity.^28,29 Such measurements quantify the extent of damage following TBI^24,30-32 and are more sensitive than conventional MR imaging to axonal injury in a mouse model of TBI.³³In a group of patients with mild TBI with persistent postconcussive symptoms, we tested the hypothesis that the extent of microstructural white matter injury on DTI would account for deficits in cognitive reaction time, whereas the number of focal lesions on conventional MR imaging would not. The purpose of this study was to determine the predominant areas of damage in mild TBI and whether the spatial extent of white matter injury on DTI can be used as an effective biomarker for global cognitive outcome.     

Comparison of three different methods for measurement of cervical cord atrophy in multiple sclerosis

BACKGROUND AND PURPOSE: Evidence is mounting that spinal cord atrophy significantly correlates with disability in patients with multiple sclerosis (MS). The purpose of this work was to validate 3 different measures for the measurement of cervical cord atrophy on high-resolution MR imaging in patients with MS and in normal control subjects (NCs). We also wanted to evaluate the relationship between cervical cord atrophy and clinical disability in the presence of other conventional and nonconventional brain MR imaging metrics by using a unique additive variance regression model.MATERIALS AND METHODS: We studied 66 MS patients (age, 41.2 ± 12.4 years; disease duration, 11.8 ± 10.7 years; Expanded Disability Status Scale, 3.1 ± 2.1) and 19 NCs (age, 30.4 ± 12.0 years). Disease course was relapsing-remitting (34), secondary-progressive (14), primary-progressive (7), and clinically isolated syndrome (11). The cervical cord absolute volume (CCAV) in cubic millimeters and 2 normalized cervical cord measures were calculated as follows: cervical cord fraction (CCF) = CCAV/thecal sac absolute volume, and cervical cord to intracranial volume (ICV) fraction (CCAV/ICV). Cervical and brain lesion volume measures, brain parenchyma fraction (BPF), and mean diffusivity were also calculated.RESULTS: CCAV (P < .0001) and CCF (P = .007) showed the largest differences between NCs and MS patients and between different disease subtypes. In regression analysis predicting disability, CCAV was retained first (R² = 0.498; P < .0001) followed by BPF (R² = 0.08; P = .08). Only 8% of the variance in disability was explained by brain MR imaging measures when coadjusted for the amount of cervical cord atrophy.CONCLUSIONS: 3D CCAV measurement showed the largest differences between NCs and MS patients and between different disease subtypes. Cervical cord atrophy measurement provides valuable additional information related to disability that is not obtainable from brain MR imaging metrics.

MR imaging of the brain is a sensitive tool for making a diagnosis of multiple sclerosis (MS). Abnormalities of brain MR imaging are present in more than 95% of patients with clinically definite MS; however, there is poor correlation between disability and the number and volume of focal brain lesions visible on MR imaging.¹Involvement of the spinal cord, especially of the cervical cord,^2,3 is of particular significance in the development of physical disability in patients with MS.^4,5 During the course of their disease, approximately 80% of patients with MS present with spinal cord symptoms.⁶ Conventional T2-weighted spinal cord imaging is sensitive in detecting spinal cord lesions and their changes over time.^7,8 However, measures of cord T2 lesion number and volume failed to show a significant relationship with disability and have poor prognostic value for disability accumulation over the mid-to-long term.^2,3 Evidence is mounting that spinal cord atrophy significantly correlates with disability.^5,9–11Atrophy of the spinal cord in MS is thought to reflect inflammatory tissue injury, demyelination, and axonal loss. Postmortem pathologic studies have documented spinal cord axonal loss in MS.^12,13 However, whereas the correlation between central nervous system atrophy and disability has been interpreted as a reflection of axonal loss in pre-existing lesions,^14–16 axonal loss does not appear to directly affect the cross-sectional cord area in pathologic studies.² Measurement of spinal cord atrophy has demonstrated value in the clinical realm. Serial MR imaging of the spinal cord has shown evidence of disease activity undetectable on clinical examination, thereby increasing the diagnostic sensitivity of MR imaging for patients with suspected MS.¹⁷ Spinal cord abnormalities on MR imaging are not restricted only to patients presenting with spinal cord symptoms, because changes suggestive of atrophy may be seen before any manifestation of clinical symptoms. It has been shown that atrophy of the cervical spinal cord is a useful measure for determining clinical disability^10,15,18 and monitoring disease progression,¹⁹ as well as therapeutic drug effects in MS.²⁰Key problems in the evaluation of spinal cord atrophy have been related to poor resolution of MR imaging, small size of the cord, and surrounding fat, bone, and CSF that can cause artifacts and, as a consequence, compromise the final image quality. Indeed, artifacts related to pulsation and respiratory cardiac motion have also been considered.^2,3 This led in most of the earlier studies to unacceptable error in manual delineation of the cord/CSF interface.² The technical challenges of spinal cord imaging posed by the size and anatomy of the cord and by its surrounding structures have been addressed in recent years by improved receiver coils, fast imaging, 3D imaging, motion suppression, and cardiac gating. Subsequently, interest has emerged in a reproducible semiautomated measurement of the cord cross-sectional area²¹ and its improved measurement by reduction of partial volume effect,²² as well as by 3D extraction of the cord surface area.²³The goal of the present study was to investigate whether spinal cord atrophy in MS may be assessed by measurement of the whole cervical cord volume rather than by the traditional cross-sectional area approach at level C2/C3. To improve the accuracy and precision of cervical cord volume measurements, a semiautomated edge detection technique was used to create a tissue-boundary map from 3D volumetric scans of the cervical cord. Therefore, the objectives of the present cross-sectional study were first to validate this original method for measuring whole cervical cord volume by comparing 19 normal control subjects (NCs) and 65 patients with MS with different disease subtypes. We also evaluated the relationship between absolute and normalized cervical cord atrophy and clinical disability in the presence of other conventional and nonconventional brain MR imaging metrics using a unique additive variance regression model.     

Head and neck paragangliomas: value of contrast-enhanced 3D MR angiography

BACKGROUND AND PURPOSE: A rapid and accurate MR imaging technique would be beneficial to assess paragangliomas in the head and neck and to distinguish them from other lesions. The purpose of this study was to determine whether the combination of elliptic centric contrast-enhanced MR angiography (CE-MRA) and unenhanced and enhanced spin-echo imaging (conventional MR imaging) is more accurate than conventional MR imaging alone to assess paragangliomas in the head and neck.MATERIALS AND METHODS: Three radiologists retrospectively and independently reviewed CE-MRA and conventional MR imaging in 27 patients with suspected paragangliomas. The overall image quality and the probability of paraganglioma were recorded. The results of each technique and their combination were analyzed for sensitivity and specificity. Receiver operating characteristic (ROC) analyses were performed by using histologic analysis, imaging, and/or clinical findings as the reference standard.RESULTS: Forty-six lesions were found in 27 patients. In the assessment of paragangliomas, the combination of conventional MR imaging and CE-MRA was significantly superior to conventional MR imaging alone. Sensitivity and specificity respectively were the following: for CE-MRA, 100% and 94%; and for conventional MR imaging, 94% and 41%. The specificity of CE-MRA was significantly higher than that of conventional MR imaging (P = .004). There was good-to-excellent interobserver agreement for the paraganglioma probability with CE-MRA (nonweighted κ, 0.67–0.77), whereas there was fair-to-good interobserver agreement with conventional MR imaging (nonweighted κ, 0.50–0.65).CONCLUSION: In combination with conventional MR imaging, CE-MRA yields an excellent diagnostic value for the assessment of head and neck paragangliomas; hence, the 2 techniques should be regarded as complementary.

In the head and neck, paragangliomas are slow-growing hypervascular lesions that are most commonly located in 4 main sites: the carotid bifurcation, the foramen jugulare, the middle ear cavity, and along the cervical portion of the vagus nerve.¹ These lesions occur in both sporadic and hereditary forms (7% of cases). Multicentricity occurs in 10% of sporadic paragangliomas and in 30%–40% of familial paragangliomas.Imaging techniques are used for suspected head and neck paragangliomas to confirm this diagnosis.² Accurate assessment of tumor margins and invasion of adjacent structures are also essential for proper staging and therapy.³ For this task, MR imaging using unenhanced and enhanced fat-suppressed spin-echo (SE) sequences is widely accepted as the method of choice,^4,5 in addition to high-resolution CT,^6,7 in particular when the skull base is involved. Nonetheless, SE MR imaging has several limitations, particularly its sensitivity to artifacts.⁸ Moreover, the differentiation from other tumors and inflammatory lesions remains problematic. For example, the results of SE imaging are often equivocal when processes in the area of the jugular foramen are suspected.^9,10 Somatostatin receptor scintigraphy (SRS) may be useful in this situation but is not always conclusive. Digital subtraction angiography (DSA) is the current imaging reference standard for assessing the vascular architecture of the tumor before embolic therapy, but this method is invasive with a complication rate of 0.5%–1%,¹¹ which is too high for a diagnostic examination. Consequently, some investigators have discussed the utility of more specific methods in MR imaging to differentiate paragangliomas from other tumors or vascular abnormalities (dynamic MR imaging,¹² high-dose gadodiamide-injection dynamic MR imaging,¹³ or arterial and venous MR angiography [MRA]⁹).To our knowledge, the elliptical centric contrast-enhanced MRA (CE-MRA) sequence has not been assessed for visualizing paragangliomas and differentiating them from other lesions. We postulated that CE-MRA has the potential to simplify the interpretation of conventional MR imaging because intense tumor blush on CE-MRA may be a sensitive and specific feature for paragangliomas.The purpose of this study was to determine whether the combination of CE-MRA and conventional MR imaging is more accurate than conventional MR imaging alone to assess patients with suspected paragangliomas.     

Nontraumatic skull base defects with spontaneous CSF rhinorrhea and arachnoid herniation: imaging findings and correlation with endoscopic sinus surgery in 27 patients

BACKGROUND AND PURPOSE: Defects at the skull base leading to spontaneous CSF rhinorrhea are rare lesions. The purpose of our study was to correlate CT and MR findings regarding the location and content of CSF leaks in 27 patients with endoscopic sinus surgery observations.MATERIALS AND METHODS: Imaging studies in 27 patients with intermittent CSF rhinorrhea (CT in every patient including 10 examinations with intrathecal contrast, plain CT in 2 patients, and MR in 15 patients) were analyzed and were retrospectively blinded to intraoperative findings.RESULTS: CT depicted a small endoscopy-confirmed osseous defect in 3 different locations: 1) within the ethmoid in 15 instances (53.6% of defects) most commonly at the level of the anterior ethmoid artery (8/15); 2) adjacent to the inferolateral recess of the sphenoid sinus in 7 patients including one patient with bilateral lesions (8/28 defects, 28.6%); 3) within the midline sphenoid sinus in 5 of 28 instances (17.9%). Lateral sphenoid defects (3.5 ± 0.80 mm) were larger than those in ethmoid (2.7 ± 0.77 mm, P ≤ 0.029) or midsphenoid location (2.4 ± 0.65 mm, P ≤ 0.026). With endoscopy proven arachnoid herniation in 24 instances as reference, MR was correct in 14 of 15 instances (93.3%), CT cisternography in 5 of 8 instances (62.5%). Plain CT in 1 patient was negative.CONCLUSION: In patients with a history of spontaneous CSF rhinorrhea, CT was required to detect osseous defects at specific sites of predilection. MR enabled differentiating the contents of herniated tissue and allowed identification of arachnoid tissue as a previously hardly recognized imaging finding.

The term “spontaneous” CSF rhinorrhea has been applied to describe nasal discharge of CSF unrelated to trauma, surgery, malformation, tumor, or previous radiation therapy.^1–4 Spontaneous CSF rhinorrhea is uncommon. Estimates of the spontaneous cause among all causes of CSF rhinorrhea are subject to variation ranging from only 6%,⁵ 11.4%,⁶ 14%,³ 21%,⁷ to 23%.⁸ Periodic release of CSF from the nose was first described by Galen in 200 B.C. and was considered a physiologic phenomenon until Thomson, in 1899, assembled 21 patients in a monograph reporting spontaneous CSF rhinorrhea as a pathologic clinical entity.^9,10Spontaneous CSF rhinorrhea has been recognized as a distinct entity with respect to clinical presentation,^2,11,12 treatment,^13–15 and propensity for recurrence.^8,16,17 As early as 1968, Ommaya et al⁹ postulated the existence of “high-pressure leaks” related to intracranial tumors and of “normal pressure leaks” occasionally associated with empty sella. The role of empty sella as an indicator of raised intracranial pressure as well was supported by the observation of elevated CSF pressure in individual patients¹¹ and in a series of 10 patients who underwent lumbar puncture after sealing of the defect.¹⁸ In addition to the presence of an empty sella as a radiologic sign,¹⁹ a common clinical constellation in patients with spontaneous CSF rhinorrhea is female sex, middle age, and obesity.^{8,14,15,18–22}Spontaneous CSF leaks have been postulated to represent a manifestation of benign intracranial hypertension²² or pseudotumor cerebri.²³ Pulsatile-increased hydrostatic pressure is capable of bone erosion during the course of many years.^2,24 To become effective as a CSF leak, bone erosion and creation of an osteodural defect is required to occur at pneumatized parts of the skull base leading to communication of the subarachnoid space with the sinonasal spaces or temporal bone cavity. Related to CSF rhinorrhea, a review of the literature up to 1972¹⁰ identified the cribriform plate, craniopharyngeal canal, sella, and spheno-occipital synchondrosis as possible sites of predilection. Arachnoid granulations in proximity to the ethmoid and sphenoid sinus have been implicated as precursors of osteodural leaks.² Accordingly, arachnoid granulations causing erosion of the temporal bone may present with CSF otorrhea.^2,25,26Among the imaging techniques used to localize the site of the fistula, radionuclide isotope cisternography and CT cisternography were of limited sensitivity in 66% of patients only.³ When active leaks were present, CT cisternography provided positive results in 85% of patients.²⁷ However, in cases of inactive fistulas, CT cisternography failed to recognize the site of leakage in 27.7%²⁸ and in 19% of patients.²⁹ Advances in CT and MR imaging techniques have improved sensitivity, which amounted to 88.25%³⁰ and 93%³¹ for high-resolution CT and for MR cisternography to 89%,^6,31 93.6%,²⁸ and 100%^32,33 even in patients with inactive leaks. Therefore, high-resolution CT, MR cisternography, or a combination of both techniques have replaced the previously used invasive procedures.A confounding nomenclature exists regarding the contents of osteodural defects such as meningocele,^10,14 meningoencephalocele,⁴ encephalocele,^11,34 meningeal or arachnoid hernia,^24,35 arachnoid diverticulum,³⁶ or arachnoid cyst.³⁷ These differing designations reflect variable contents of herniation and occasional inaccuracy because of the limited ability to visualize the lesions by imaging^24,29 and during transcranial surgery.^1,10 Knowledge of the contents of herniation may modify the grafting technique and therefore facilitates preoperative planning.¹⁶ The endoscopic skull base approach has rendered direct visualization of the defect and its contents feasible.^38–40 Therefore, endoscopy was chosen as a standard of reference in this study. CT and MR findings in this series of patients with spontaneous CSF rhinorrhea were particularly assessed regarding the contents of herniation and location and correlated with endoscopy. Predisposing factors (arachnoid granulation, empty sella) and the size of the osseous defect were assessed on CT images.     

Sixty-four-section CT cerebral perfusion evaluation in patients with carotid artery stenosis before and after stenting with a cerebral protection device

BACKGROUND AND PURPOSE: Brain tissue viability depends on cerebral blood flow (CBF) that has to be kept within a narrow range to avoid the risk of developing ischemia. The aim of the study was to evaluate by 64-section CT (VCT) the cerebral perfusion modifications in patients with severe carotid stenosis before and after undergoing carotid artery stent placement (CAS) with a cerebral protection system.MATERIALS AND METHODS: Fifteen patients with unilateral internal carotid stenosis (≥70%) underwent brain perfusional VCT (PVCT) 5 days before and 1 week after the stent-placement procedure. CBF and mean transit time (MTT) values were measured.RESULTS: Decreased CBF and increased MTT values were observed in the cerebral areas supplied by the stenotic artery as compared with the areas supplied by the contralateral patent artery (P < .001). A significant normalization of the perfusion parameters was observed after the stent-placement procedure (mean pretreatment MTT value, 5.3 ± 0.2; mean posttreatment MTT value, 4.3 ± 0.18, P < .001; mean pretreatment CBF value, 41.2 mL/s ± 2.1; mean posttreatment CBF value, 47.9 mL/s ± 2.9, P < .001).CONCLUSIONS: PVCT is a useful technique for the assessment of the hemodynamic modifications in patients with severe carotid stenosis. The quantitative evaluation of cerebral perfusion makes it a reliable tool for the follow-up of patients who undergo CAS.

Carotid artery stenosis, with its thromboembolic complications causing cerebral ischemia,^1,2 can be successfully treated by carotid endarterectomy (CEA), which significantly reduces the risk of stroke in both symptomatic and asymptomatic patients, as compared with medical therapy alone.^3,4 Alternatively, carotid artery stent placement (CAS) is increasingly used thanks to the development of safe and effective protection systems that help reduce the periprocedural neurologic complications.^5,6 Two recent registry studies (ARCHeR, Caress) have demonstrated that CEA and CAS are comparable in terms of periprocedural complications in symptomatic or asymptomatic patients not presenting comorbidities.^7,8 The overlapping percentage of complications between these 2 techniques at 30 days is 2%.Cerebral perfusion changes, such as an asymmetry in the hemisphere corresponding to the affected carotid artery, have been observed in patients with unilateral severe carotid stenosis, however without a direct correlation to the degree of stenosis.^9,10 A measure of perfusion disturbance as provided by cerebral blood flow (CBF) and mean transit time (MTT) appears to be helpful in evaluating brain with a risk of developing a stroke and eventually in guiding the therapeutic decisions especially in acute ischemic events.¹¹Positron-emission tomography (PET), single-photon emission CT (SPECT), xenon-enhanced CT (Xe-CT), perfusion CT (PCT), and MR imaging have all been applied in the study of brain hemodynamics. However, the scarce availability of PET and SPECT in most radiology departments or the difficulty in obtaining a quantitative measurement by MR imaging has drawn attention for >20 years toward Xe-CT,¹² whose demonstrated accurate measurement of perfusion¹³ has permitted the differentiation of patients with normal CBF¹⁴ from those with reversible neurologic deficits (CBF, 10–20 mL/100 g per minute) or those with infarction (CBF < 10 mL/100 g per minute).¹³ PCT, validated by comparison with Xe-CT^13,14 and widely available in most radiology departments, can be easily performed at the end of a CT scanning and has, therefore, further simplified the approach to brain perfusion evaluation,^15,16 adding further information about hemodynamic parameters such as MTT and cerebral blood volume. More recently, the perfusion study by 64-section CT (VCT), allowing the assessment of a brain volume ≤4 cm, has offered an improved tool of investigation.The aim of our study was to measure by brain perfusional VCT (PVCT) the hemodynamic parameters in the cerebral hemisphere supplied by the severely stenotic internal carotid artery (ICA), in a group of patients undergoing an endovascular treatment with a protection device. The hypothesis is that CBF and MTT values in the hemisphere on the side of the carotid stenosis will be abnormal before the procedure and will approach the values on the contralateral side after the procedure.