Posterior reversible encephalopathy syndrome after solid organ transplantation

BACKGROUND AND PURPOSE: Posterior reversible encephalopathy syndrome (PRES) is known to occur after solid organ transplantation (SOT), potentially associated with cyclosporine and tacrolimus. In this study, we assess the frequency and clinical and imaging characteristics of PRES after SOT.MATERIALS AND METHODS: We identified 27 patients (13 men and 14 women; age range, 22–72 years) who developed PRES after SOT. Features noted included SOT subtype, incidence and timing of PRES, infection and rejection, mean arterial pressure (MAP), and toxicity brain edema.RESULTS: PRES developed in 21 (0.49%) of 4222 patients who underwent transplantation within the study period (no significant difference among SOT subtypes). Transplantation was performed in 5 patients before the study period, and 1 patient underwent transplantation elsewhere. In consideration of all 27 patients, PRES typically developed in the first 2 months in patients who had SOT of the liver (9 of 10 patients) and was associated with cytomegalovirus (CMV), mild rejection, or systemic bacterial infection. PRES also typically developed after 1 year in patients who had SOT of the kidney (8 of 9 patients) and was associated with moderate rejection or bacterial infection. Toxicity MAP was significantly lower (P < .001) in liver transplants (average MAP, 104.8 ± 16 mm Hg) compared with that in kidney transplants (average MAP, 143 ± 20 mm Hg). Toxicity brain edema was significantly greater (P < .001) in patients who had liver transplants and developed PRES compared with patients who had undergone kidney transplants despite severe hypertension in those who had the kidney transplants.CONCLUSION: Patients who had undergone SOTs have a similar low incidence of developing PRES. Differences between those who have had liver and kidney transplants included time after transplant, toxicity MAP, and PRES vasogenic edema noted at presentation. In patients who have undergone kidney transplants, severely elevated MAP was associated with reduced, not greater, brain edema.

Neurotoxicity with the development of the posterior reversible encephalopathy syndrome (PRES) imaging pattern is most typically noted in solid organ transplantation (SOT), allogeneic bone marrow transplantation (allo-BMT), and eclampsia.^1–17 PRES is also seen in association with infection, sepsis, shock, autoimmune disease, and after chemotherapy.^18–27 Patients develop headache, visual disturbance, or altered mentation, which often progress to seizure.²⁸ Severe hypertension is commonly present, but patients may be normotensive (20% to 30%).^3,29,30On CT or MR imaging, vasogenic edema is typically present in the occipital and parietal regions but also in the frontal lobes (in particular, along the superior frontal sulcus), inferior temporo-occipital junction, and cerebellar hemispheres.^1,3,18,19,31 Involvement of the deep white matter (WM), basal ganglia, and brain stem is also seen, with areas of restricted diffusion and focal hemorrhage occasionally noted.^4,6,31Although many case reports have described PRES or cyclosporine and tacrolimus neurotoxicity in SOT, to our knowledge, a comprehensive assessment has not been performed. The purpose of this retrospective study was to evaluate the incidence of PRES after SOT along with the clinical and imaging features of PRES neurotoxicity in a large population of patients who have undergone SOT.     

Follow-up of coiled cerebral aneurysms at 3T: comparison of 3D time-of-flight MR angiography and contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: Our aim was to compare contrast-enhanced MR angiography (CE-MRA) and 3D time-of-flight (TOF) MRA at 3T for follow-up of coiled cerebral aneurysms.MATERIALS AND METHODS: Fifty-two patients treated with Guglielmi detachable coils for 54 cerebral aneurysms were evaluated at 3T MRA. 3D TOF MRA (TR/TE = 23/3.5; SENSE factor = 2.5) and CE-MRA by using a 3D ultrafast gradient-echo sequence (TR/TE = 5.9/1.8; SENSE factor = 3) enhanced with 0.1-mmol/kg gadobenate dimeglumine were performed in the same session. Source images, 3D maximum intensity projection, 3D shaded surface display, and/or 3D volume-rendered reconstructions were evaluated in terms of aneurysm occlusion/patency and artifact presence.RESULTS: In terms of clinical classification, the 2 MRA sequences were equivalent for 53 of the 54 treated aneurysms: 21 were considered fully occluded, whereas 16 were considered to have a residual neck and 16 were considered residually patent at follow-up MRA. The remaining aneurysm appeared fully occluded at TOF MRA but had a residual patent neck at CE-MRA. Visualization of residual aneurysm patency was significantly (P = .001) better with CE-MRA compared with TOF MRA for 10 (31.3%) of the 32 treated aneurysms considered residually patent with both sequences. Coil artifacts were present in 5 cases at TOF MRA but in none at CE-MRA. No relationship was apparent between the visualization of patency and either the size of the aneurysm or the interval between embolization and follow-up.CONCLUSION: At follow-up MRA at 3T, unenhanced TOF and CE-MRA sequences are similarly effective at classifying coiled aneurysms as occluded or residually patent. However, CE-MRA is superior to TOF MRA for visualization of residual patency and is associated with fewer artifacts.

Regular imaging follow-up of patients with intracranial aneurysms treated with Guglielmi detachable coils (GDCs) is necessary because of the risk of aneurysm reconfiguration (ie, coil compaction and/or growth of a residual aneurysm neck or body remnant) with time.^1–4 Of the techniques available for monitoring the results of embolization therapy, MR angiography (MRA) has emerged as the technique of choice at most institutions. Advantages over conventional digital subtraction angiography (DSA) include minimal invasiveness with no associated risk of neurologic complications, reduced patient discomfort and inconvenience, greater cost savings, and no exposure to ionizing radiation or potentially nephrotoxic iodinated contrast media. An alternative minimally invasive procedure is CT angiography (CTA). However, whereas this technique has proved useful for aneurysm detection,^5–9 limitations to its use for follow-up of coiled aneurysms include streak and other coil-related artifacts.^10–12 Moreover, CTA also requires exposure to ionizing radiation and iodinated contrast media, which may be undesirable if repeat follow-up examinations are required.Studies performed to date have shown that nonenhanced 3D time-of-flight (TOF) MRA sequences on 1.5T scanners are frequently satisfactory for the follow-up of coiled aneurysms^1–20 but that 3D TOF MRA on 3T scanners offers improved depiction of both treated²¹ and untreated²² aneurysms due to the greater spatial and contrast resolution achievable at a higher magnetic field strength. Concerning the use of gadolinium contrast material, some studies have suggested that contrast-enhanced MRA (CE-MRA) provides no additional benefit compared with nonenhanced 3D TOF MRA at either 1.5T^15,20 or 3T,²¹ whereas other studies have shown that CE-MRA permits better visualization of coiled aneurysms and of branch arteries and residual neck, particularly in large or giant aneurysms.^14,22–26 Recently, Nael et al²⁷ demonstrated that CE-MRA with highly accelerated (×4) parallel acquisition at 3T provides comparable information to accelerated (×2) 3D TOF MRA at 3T for the characterization of untreated intracranial aneurysms without the known drawbacks of TOF MRA techniques (ie, prolonged acquisition time, spin saturation, and flow-related artifacts). On the other hand, Gibbs et al²⁸ showed that with elliptic-centric imaging, 3D TOF MRA at 3T is superior to CE-MRA at 3T in terms of both image quality and detection of untreated intracranial aneurysms. Our study was performed to evaluate CE-MRA with accelerated (×3) parallel acquisition at 3T compared with accelerated (×2.5) 3D TOF MRA at 3T for the follow-up of GDC-treated intracranial aneurysms. To the authors’ knowledge, this is the first study to compare MRA sequences at 3T for follow-up of coiled aneurysms.     

Comparison of multidetector CT angiography and MR imaging of cervical artery dissection

BACKGROUND AND PURPOSE: Conventional angiography has been historically considered the gold standard for the diagnosis of cervical artery dissection, but MR imaging/MR angiography (MRA) and CT/CT angiography (CTA) are commonly used noninvasive alternatives. The goal of this study was to compare the ability of multidetector CT/CTA and MR imaging/MRA to detect common imaging findings of dissection.MATERIALS AND METHODS: Patients in the data base of our Stroke Center between 2003 and 2007 with dissections who had CT/CTA and MR imaging/MRA on initial work-up were reviewed retrospectively. Two neuroradiologists evaluated the images for associated findings of dissection, including acute ischemic stroke, luminal narrowing, vessel irregularity, wall thickening/hematoma, pseudoaneurysm, and intimal flap. The readers also subjectively rated each vessel on the basis of whether the imaging findings were more clearly displayed with CT/CTA or MR imaging/MRA or were equally apparent.RESULTS: Eighteen patients with 25 dissected vessels (15 internal carotid arteries [ICA] and 10 vertebral arteries [VA]) met the inclusion criteria. CT/CTA identified more intimal flaps, pseudoaneurysms, and high-grade stenoses than MR imaging/MRA. CT/CTA was preferred for diagnosis in 13 vessels (5 ICA, 8 VA), whereas MR imaging/MRA was preferred in 1 vessel (ICA). The 2 techniques were deemed equal in the remaining 11 vessels (9 ICA, 2 VA). A significant preference for CT/CTA was noted for VA dissections (P < .05), but not for ICA dissections.CONCLUSION: Multidetector CT/CTA visualized more features of cervical artery dissection than MR imaging/MRA. CT/CTA was subjectively favored for vertebral dissection, whereas there was no technique preference for ICA dissection. In many cases, MR imaging/MRA provided complementary or confirmatory information, particularly given its better depiction of ischemic complications.

Dissection of the extracranial arteries accounts for 10%–25% of strokes in young and middle-aged patients.¹ It may be spontaneous or traumatic and can cause a variety of clinical presentations, including stroke, headache, neck pain, tinnitus, Horner syndrome, and cranial neuropathies.^1-4 Dissections are typically diagnosed on the basis of a combination of the clinical presentation, imaging studies (conventional angiography, CT/CT angiography [CTA], MR imaging/MR angiography [MRA], and sonography), and exclusion of other arterial disease, particularly atherosclerosis.^1,2,5 In patients with mild or atypical symptoms, noninvasive imaging may facilitate earlier diagnosis and prevent embolic ischemic complications with the use of antithrombotic therapy.^3,6Conventional angiography has historically been considered the gold standard for dissection diagnosis, but it has limitations, which include its cost and invasiveness.^1,7,8 Although the angiographic appearance of dissection is often characteristic, it does not assess the vessel wall for intramural hematoma; because of this feature, dissections in unusual locations or with atypical morphology may be misclassified or attributed to other processes. MR imaging/MRA and CT/CTA have emerged as viable alternatives for both diagnosis and follow-up of dissection.^9-15 In general, the 2 techniques have different strengths and weaknesses. Diffusion-weighted MR imaging is a powerful technique for detecting acute stroke,¹⁶ which may then lead to increased scrutiny of the upstream arterial tree. Axial T1-weighted fat-suppressed images can detect the methemoglobin of the intramural hematoma within the false lumen, a finding referred to as a crescent sign.^9,13 Multidetector CT/CTA has enabled routine acquisition of thinner sections with rapid imaging times, facilitating multiplanar and volume reconstructions. Additionally, it is more widely available (especially at night), has fewer contraindications, and provides greater spatial resolution than MR imaging/MRA. However, the use of ionizing radiation in the relatively young population of patients with dissection is potentially concerning, especially given the often frequent follow-up studies in these patients.Only 1 study to date has compared CT/CTA with MR imaging/MRA for evaluation of dissection, retrospectively reviewing 7 internal carotid dissections and showing CTA to be marginally more effective in the identification of the dissected vessel.¹¹ To our knowledge, this current study is the largest comparative series of cervical artery dissection imaged with both tomographic techniques. Given the higher spatial resolution of CT/CTA, we hypothesized that CT/CTA may be particularly suited to visualize dissections within the smaller vertebral arteries. Additionally, we hypothesized that in a series of known dissections, CT/CTA would be more sensitive to identify specific imaging features associated with dissections.     

Assessment of craniospinal arteriovenous malformations at 3T with highly temporally and highly spatially resolved contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: Patients with arteriovenous malformation (AVM) are known to have an elevated risk of complications with conventional catheter angiography (CCA) but nonetheless require monitoring of hemodynamics. Thus, we aimed to evaluate both anatomy and hemodynamics in patients with AVM noninvasively by using contrast-enhanced MR angiography (CE-MRA) at 3T and to compare the results with CCA.MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained for this Health Insurance Portability and Accountability Act–compliant study. Twenty control subjects without vascular malformation (6 men, 18–70 years of age) and 10 patients with AVMs (6 men, 20–74 years of age) underwent supra-aortic time-resolved and high-spatial-resolution CE-MRA at 3T. Large-field-of-view coronal acquisitions extending from the root of the aorta to the cranial vertex were obtained for both MRA techniques. Image quality was assessed by 2 specialized radiologists by using a 4-point scale. AVM characteristics and nidus size were evaluated by using both CE-MRA and CCA in all patients.RESULTS: In patients, 96.6% (319/330) of arterial segments on high-spatial-resolution MRA and 87.7% (272/310) of arterial segments on time-resolved MRA were graded excellent/good. MRA showed 100% specificity for detecting feeding arteries and venous drainage (n = 8) and complete obliteration of the AVM in 2 cases (concordance with CCA). Nidus diameters measured by both MRA and CCA resulted in a very strong correlation (r = 0.99) with a mild overestimation by MRA (0.10 cm by using the Bland-Altman plot).CONCLUSION: By combining highly temporally resolved and highly spatially resolved MRA at 3T as complementary studies, one can assess vascular anatomy and hemodynamics noninvasively in patients with AVM.

Craniospinal arteriovenous malformation (AVM) typically presents in a young adult with intracranial hemorrhage (30%–82%), headache, seizures, or focal neurologic deficits that are either related to mass effect or to vascular steal phenomena.¹ Hemorrhage occurs with an annual incidence of 2%–4%^2,3 and remains the prime vector for mortality and morbidity (10% and 16%–50%, respectively).^4–6 Several investigators have identified features predictive of hemorrhage, including small nidus size, deep nidus location, single deep venous drainage, associated arterial aneurysm, impaired venous drainage, and high intranidal pressure.^7–10 Safe and accurate diagnostic work-up is essential to provide an architectural map and to define hemodynamic indices and risk predictors. Moreover, follow-up studies may be required for monitoring posttherapy. The current gold standard for assessment of AVM is conventional catheter angiography (CCA), which is associated with ≤1.3% of major complications and death (<0.1%).^11–13 In this context, multiple catheter examinations in patients with AVM are expected to elevate the risk of complications and hemorrhage.Recent advances in the performance of contrast-enhanced MR angiography (CE-MRA) at 3T have underscored its growing potential for detailed evaluation of the supra-aortic arteries and veins.^14–16 Techniques have been established for both highly temporally resolved and highly spatially resolved CE-MRA, by using only modest contrast doses.^17,18 Whereas high-spatial-resolution MRA can quickly provide detailed images of intracranial and extracranial vessels, time-resolved MRA adds hemodynamic information and can capture transient processes, such as early venous filling, which is the hallmark of an arteriovenous fistula (AVF).^17,19 Moreover, cortical venous reflux has a high yearly risk of hemorrhage^20–24 and influences treatment.^24–28 Micro-AVMs as a potential source of fatal intracranial hematoma represent approximately 8%–10% of surgically treated brain AVMs.^29,30 Time-resolved MRA may potentially identify an early filling vein in a micro-AVF because the anatomy of a very small nidus may not be assessable. Furthermore, an early filling vein may be the only evidence of a residual shunt after radiosurgery or endovascular therapy.These 2 approaches can, therefore, provide complementary diagnostic information to each other for evaluation of high-flow AVMs. The purpose of our study was to evaluate the potential of these complementary modes in defining the relevant vascular anatomy and hemodynamics noninvasively in patients with AVM and to compare the findings with those on digital subtraction angiography (DSA).     

Assessment of dural arteriovenous fistulas of the cavernous sinuses on 3D dynamic MR angiography

BACKGROUND AND PURPOSE: Flow voids within the cavernous sinuses and/or certain venous drainage on spin-echo MR imaging and time-of-flight (TOF) flow enhancement on MR angiography (MRA) have indicated high-velocity shunt flow and have been used for screening patients with dural arteriovenous fistulas (DAVFs) of the cavernous sinuses. In this investigation, the capabilities of 3D dynamic MRA as a flow-independent approach and those of conventional MR imaging techniques were compared with selective angiography for the diagnosis of DAVFs of the cavernous sinuses.MATERIALS AND METHODS: This retrospective study involved 18 patients with angiographically proved DAVFs of the cavernous sinuses and 12 control subjects. Sixteen partially overlapping sequential MR images were acquired on contrast-enhanced 3D dynamic MRA between the petrosal bone and the orbital roof. Two experienced observers blinded to the clinical data and results of angiography independently graded 3D dynamic MRA, fast spin-echo T2-weighted imaging (FSE T2WI), and TOF MRA.RESULTS: The average area under the receiver operating characteristic curve values and interobserver κ scores for the diagnosis of DAVFs on 3D dynamic MRA, FSE T2WI, and TOF MRA were 0.99, 0.89, and 0.95; and 0.92, 0.71, and 0.73, respectively. Those for the diagnosis of anterior, posterior, and retrograde cortical venous drainage on 3D dynamic MRA were 0.72, 0.95, and 0.81; and 0.56, 0.50, and 0.49, respectively.CONCLUSION: In this small series, screening 3D dynamic MRA directly demonstrates DAVFs of the cavernous sinuses and has improved diagnostic capability.

In patients with the classic triad of pulsating exophthalmos, orbital bruit, and conjunctival chemosis, the clinical diagnosis of arteriovenous fistulas (AVFs) of the cavernous sinuses is not difficult, and cerebral angiography is performed for definitive diagnosis. However, dural AVFs (DAVFs) without anterior drainage may not cause typical congestive orbito-ocular features, and thrombosis of the draining veins may lead to spontaneous resolution of the disorder.^1–6 Therefore, it is desirable to perform less invasive diagnostic examinations before conventional angiography. So far, flow voids within the cavernous sinuses and/or inferior petrosal sinuses on spin-echo MR images followed by time of flight (TOF) flow enhancement on source images of MR angiography (MRA) have been indicative of AVF.^7–10 Although these are safe and practical methods, dependence on flow velocity sometimes makes it impossible to distinguish fast normal flow from abnormal shunt flow or slow abnormal shunt flow from normal flow.^9–13The recent advancement of MR imaging technology has allowed first-pass contrast-enhanced dynamic MRA and 2D MR digital subtraction angiography to be applied to cerebral arteriovenous malformations (AVMs) or DAVFs.^14–18 In addition, although the conventional use of 3D dynamic MRA for their diagnosis has been difficult due to the limitation of low temporal resolution, its application has been described in recently published articles.^19,20 However, until now, there has not been a comparative study of dynamic MRA and conventional MR imaging for the diagnosis of DAVFs of the cavernous sinuses.According to a study of dynamic CT of the cavernous sinuses²¹ and physiologic studies on the cerebral circulation time,^22,23 it was hypothesized that imaging temporal resolution under several seconds would demonstrate DAVFs of the cavernous sinuses on dynamic MRA. Therefore, we used the 3D data-acquisition technique, a standard pulse sequence, and postulated that early enhancement of the cavernous sinuses was a main direct feature of the shunts. This methodology will improve the diagnostic capability for screening of DAVFs of the cavernous sinuses.     

3D time-resolved MR angiography (MRA) of the carotid arteries with time-resolved imaging with stochastic trajectories: comparison with 3D contrast-enhanced Bolus-Chase MRA and 3D time-of-flight MRA

BACKGROUND AND PURPOSE: Time-resolved MR angiography (MRA) offers the combined advantage of large anatomic coverage and hemodynamic flow information. We applied parallel imaging and time-resolved imaging with stochastic trajectories (TWIST), which uses a spiral trajectory to undersample k-space, to perform time-resolved MRA of the extracranial internal carotid arteries and compare it to time-of-flight (TOF) and high-resolution contrast-enhanced (HR) MRA.MATERIALS AND METHODS: A retrospective review of 31 patients who underwent carotid MRA at 1.5T using TOF, time-resolved and HR MRA was performed. Images were evaluated for the presence and degree of ICA stenosis, reader confidence, and number of pure arterial frames attained with the TWIST technique.RESULTS: With a consensus interpretation of all sequences as the reference standard, accuracy for identifying stenosis was 90.3% for TWIST MRA, compared with 96.0% and 88.7% for HR MRA and TOF MRA, respectively. HR MRA was significantly more accurate than the other techniques (P < .05). TWIST MRA yielded datasets with high in-plane spatial resolution and distinct arterial and venous phases. It provided dynamic information not otherwise available. Mean diagnostic confidence was satisfactory or greater for TWIST in all patients.CONCLUSION: The TWIST technique consistently obtained pure arterial phase images while providing dynamic information. It is rapid, uses a low dose of contrast, and may be useful in specific circumstances, such as in the acute stroke setting. However, it does not yet have spatial resolution comparable with standard contrast-enhanced MRA.

Stroke has an estimated prevalence of 5.7 million (2.6%) adults in the United States, where it is the third most common cause of mortality.¹ Atherosclerotic carotid artery disease is an important risk factor for anterior circulation ischemic stroke. Imaging evaluation is essential for optimal management and stroke prevention, as demonstrated in studies of symptomatic^2,3 and asymptomatic populations.^4,5 Carotid dissection is another potential cause of anterior circulation ischemia, which also requires high-spatial-resolution imaging for definitive diagnosis.Digital subtraction angiography (DSA) remains the gold standard for assessment of the cervical vasculature,⁶ with excellent spatial and temporal resolution. However, risks include vascular injury, intracerebral complications, contrast nephrotoxicity, and exposure to ionizing radiation. Therefore, noninvasive techniques are typically used initially. Duplex Doppler sonography, CT angiography (CTA), and MR angiography (MRA) all have high but varying degrees of sensitivity and specificity, ranging from 70% to 99% for carotid stenosis detection.⁷ Although sonography provides excellent dynamic information and spatial resolution, insonation window limitations restrict anatomic coverage. Similarly, long imaging times with time-of-flight (TOF) MRA also limit anatomic coverage. CTA and conventional arterial contrast-enhanced MRA offer extensive coverage but provide no dynamic information and are dependent on accurate timing for optimal visualization of the arterial tree.3D time-resolved contrast-enhanced MR angiography (TR MRA) has been previously described.⁸ TR MRA offers combined anatomic and hemodynamic information and obtains pure arterial and venous phase images consistently and rapidly without a timing run. More recently, the technique has been specifically applied to the extracranial carotid arteries using parallel imaging or keyhole imaging techniques.^9,10 In this study, we report the diagnostic accuracy of TR MRA of the extracranial internal carotid artery (ICA) acquired with a combination of parallel imaging (generalized autocalibrating partially parallel acquisition [GRAPPA])¹¹ and time-resolved imaging with stochastic trajectories (TWIST), a new view-sharing technique, which undersamples the periphery of k-space depending on the radial distance from the center of k-space.^12,13 We compared TR MRA with 3D high-resolution contrast enhanced MRA (HR MRA) and 3D TOF MRA.     

Characterization of aneurysm remnants after endovascular treatment: contrast-enhanced MR angiography versus catheter digital subtraction angiography

BACKGROUND AND PURPOSE: A substantial percentage of coiled aneurysms are associated with persistent filling of an aneurysmal component due to incomplete initial treatment or re-growth. Traditionally follow-up of coiled aneurysms has consisted of repeated intra-arterial cerebral catheter angiography, an invasive procedure with associated risks. Hence, many authors have advocated the use of non-invasive imaging techniques for this purpose. Our aim was to compare contrast-enhanced MR angiography (CE-MRA) with digital subtraction angiography (DSA) for depiction of aneurysmal remnants of coiled cerebral aneurysms.MATERIALS AND METHODS: Aneurysms coiled between September 2003 and October 2006 were retrospectively reviewed. We included patients meeting the following criteria: 1) residual/recurrent aneurysm measuring 2 mm or greater, and 2) CE-MRA and DSA performed no more than 60 days apart. Three readers were asked to determine which technique was superior for characterization of the aneurysmal remnant: CE-MRA, DSA, or indeterminate. Statistical analysis included most rule and κ statistics.RESULTS: Of 232 patients who underwent coiling, 44 met the inclusion criteria (33 women and 11 men; 24–72 years of age). Sixteen patients had neck remnants and 28 had body remnants. The first study to identify the remnant was DSA in 35 patients and CE-MRA in 9. In 32 patients (32/44, 73%), the readers indicated that CE-MRA was superior to DSA for remnant characterization. CE-MRA and DSA were thought to be equivalent in 7 (16%), and DSA was preferred in 3 (7%). Two cases (5%) yielded ambiguous results. Of the 28 body remnants, 22 (78.6%) were characterized by remnant protrusion into the coil mass: In 20 of these (91%), the readers preferred CE-MRA over DSA, and in 2 cases (9%), the techniques were thought to be equivalent.CONCLUSION: In patients with known aneurysm remnants, CE-MRA is at least equivalent to DSA for characterization of aneurysmal remnants after coiling. Contrast filling within the coil mass was more clearly seen with CE-MRA than with DSA.

Since the publication of the International Subarachnoid Aneurysm Trial,¹ intracranial aneurysms are increasingly treated with endovascular coiling. A substantial percentage of coiled aneurysms are associated with persistent filling of an aneurysmal component either due to incomplete initial treatment or regrowth.^1,2 Reconfiguration of the coil mass with time results in a recurrent aneurysmal neck or body remnant,^3,4 which leads to reperfusion of the aneurysm, exposing the patient to a risk of rupture and rebleeding.¹ For this reason, follow-up imaging (surveillance) of coiled aneurysms is important. When a considerable aneurysmal remnant is identified, recoiling is commonly advised. Traditionally this surveillance has consisted of repeated digital substraction angiography (DSA) in the months and years following the initial endovascular coiling. DSA is, however, an invasive procedure with well-known associated risks.⁵ Additional disadvantages include a short postprocedural hospital stay, radiation exposure, allergic or nephrotoxic effects of iodinated contrast medium, and patient discomfort and expense. Hence, many authors have developed and advocated the use of noninvasive imaging techniques for the surveillance of aneurysm postcoiling.^6-15The accuracy and reliability of contrast-enhanced MR angiography (CE-MRA) to identify an aneurysm recurrence in coiled patients has been established.^6,7,10,13 Although it is now recognized that CE-MRA is not devoid of risks,^16,17 these risks are negligible and avoidable, compared with those of DSA. The purpose of this trial was to further evaluate the performance of CE-MRA for the depiction of the size and configuration of these aneurysmal remnants compared with DSA (the gold standard). This trial will help further define the role of noninvasive imaging in the surveillance of patients with previously coiled aneurysms.     

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.     

Association between cerebral microbleeds on T2*-weighted MR images and recurrent hemorrhagic stroke in patients treated with warfarin following ischemic stroke

BACKGROUND AND PURPOSE: Although accumulating evidence suggests the presence of microbleeds as a risk factor for intracerebral hemorrhage (ICH), little is known about its significance in anticoagulated patients. The aim of this study was to determine whether the presence of microbleeds is associated with recurrent hemorrhagic stroke in patients who had received warfarin following atrial fibrillation–associated cardioembolic infarction.MATERIALS AND METHODS: A total of 87 consecutive patients with acute recurrent stroke, including 15 patients with ICH and 72 patients with cerebral infarction, were enrolled in this study. International normalized ratios (INRs), vascular risk factors, and imaging characteristics, including microbleeds on T2*-weighted MR images and white matter hyperintensity (WMH) on T2-weighted MR images, were compared in the 2 groups.RESULTS: Microbleeds were noted more frequently in patients with ICH than in patients with cerebral infarction (86.7% versus 38.9%, P = .0007). The number of microbleeds was larger in patients with ICH than in patients with cerebral infarction (mean, 8.4 versus 2.1; P = .0001). INR was higher in patients with ICH than in patients with cerebral infarction (mean, 2.2 versus 1.4; P < .0001). The frequency of hypertension was higher in patients with ICH than in patients with cerebral infarction (86.7% versus 45.8%, P = .0039). Multivariate analysis revealed that the presence of cerebral microbleeds (odds ratio, 7.383; 95% confidence interval, 1.052–51.830) was associated with ICH independent of increased INR and hypertension.CONCLUSION: The presence of cerebral microbleeds may be an independent risk factor for warfarin-related ICH, but more study is needed because of strong confounding associations with elevated INR and hypertension.

One of the major complications of warfarin treatment following atrial fibrillation–related cardioembolic infarction is the occurrence of intracerebral hemorrhage (ICH). With advancing age, the incidence of both atrial fibrillation–related cardioembolic infarction and warfarin-related ICH increases.Cerebral microbleeds detected by gradient-echo T2*-weighted MR imaging, which are shown as signal-intensity loss, represent hemosiderin deposit^1,2 and are associated with occurrence of ICH.^3–19 Although accumulating evidence suggests that the presence of microbleeds is a risk factor for ICH in patients treated by antiplatelet therapy^13,20 and hemorrhagic complications of anticoagulation in patients with prior ICH and atrial fibrillation have been reported,²¹ little is known about the significance of microbleeds in anticoagulated patients because, to our knowledge, no studies have focused on the association between cerebral microbleeds and anticoagulation therapy in a large number of patients. On the other hand, previous studies focusing on radiographic characteristics have shown that the presence of microangiopathy (leukoaraiosis) detected by CT is a risk factor for warfarin-related ICH.²² However, considering the close association between cerebral microbleeds and leukoaraiosis (white matter hyperintensity [WMH]),^{7,8,11,14–16,19,23,24} one could hypothesize that cerebral microbleeds, which represent bleeding from small vessels, may be more closely associated with ICH than WMH is. Therefore, the present study was performed to determine whether the presence of microbleeds is associated with recurrent hemorrhagic stroke in patients who have received warfarin treatment following atrial fibrillation–associated cardioembolic infarction.     

Stability of intracranial aneurysms adequately occluded 6 months after coiling: a 3T MR angiography multicenter long-term follow-up study

BACKGROUND AND PURPOSE: The long-term fate of coiled intracranial aneurysms is largely unknown, and prolonged imaging follow-up has been advocated. The yield of follow-up imaging in coiled aneurysms adequately occluded at 6 months is unknown. In such patients, we performed time-of-flight MR angiography (MRA) to assess the incidence and therapeutic consequences of reopening 5–11 years after coiling.MATERIALS AND METHODS: Between 1995 and 2002, 661 aneurysms in 607 patients were coiled in 3 participating centers. Six-month follow-up angiograms were obtained in 497 (75%) aneurysms, of which 316 (64%) in 297 patients were adequately occluded. Of 297 patients, 84 were excluded for various reasons and 73 could not be traced. Of 140 eligible patients, 104 (74%) with 111 aneurysms were studied with 3T MR imaging and high-resolution MRA at a mean of 6.0 years after coiling (median, 5.6 years; range, 5.0–10.6 years).RESULTS: The proportion of aneurysms with reopening was 3.6% (4/111; 95% confidence interval [CI], 1.1%–9.2%). One reopened aneurysm, which initially contained intraluminal thrombus, was additionally coiled (0.9%; 95% CI, 0.0%–5.4%).CONCLUSION: In intracranial aneurysms with adequate occlusion at 6 months after coiling, the proportion of reopening needing retreatment after >5 years is low. The number of reopened aneurysms with therapeutic consequences was too small to assess risk factors, but probably the presence of intraluminal thrombus is one such risk factor. Most patients with coiled intracranial aneurysms that are adequately occluded at 6 months might not need prolonged imaging follow-up.

Endovascular embolization with detachable coils has become an established technique for the treatment of patients with intracranial aneurysms.^1,2 In approximately 15%–40% of patients, the coiled aneurysm reopens at follow-up due to coil compaction or resolution of intraluminal thrombus.^3-13 The most important and constantly found risk factors for reopening with time are large aneurysm size, low packing attenuation, initial incomplete occlusion, and the initial presence of intraluminal thrombus. Risk factors in some but not all studies are rupture status, aneurysm location, and neck size. In several studies, more first-time recurrences were found with longer follow-up.^4,5,8 In contrast, we found in a previous study of 164 aneurysms with angiographic follow-up at fixed intervals of 6 and 18 months that all aneurysm recurrences were apparent at first angiographic follow-up and aneurysms that were adequately occluded at 6 months remained so at the 18-month interval.³ We postulate that if this stability of aneurysm occlusion between 6 and 18 months could be confirmed in a longer follow-up study, it could have important consequences for the follow-up strategy of coiled intracranial aneurysms. In this long-term follow-up study, we performed 3T MR imaging and MR angiography (MRA), 5–11 years after coiling, in a sample of a large multicenter cohort of patients with aneurysms that were adequately occluded at first angiographic follow-up at 6 months to assess the incidence and therapeutic consequences of long-term reopening.     

Diagnostic accuracy of CT angiography with matched mask bone elimination for detection of intracranial aneurysms: comparison with digital subtraction angiography and 3D rotational angiography

BACKGROUND AND PURPOSE: Our aim was to determine the diagnostic accuracy of multisection CT angiography combined with matched mask bone elimination (CTA-MMBE) for detection of intracranial aneurysms compared with digital subtraction angiography (DSA) and 3D rotational angiography (3DRA).MATERIALS AND METHODS: Between January 2004 and February 2006, 108 patients who presented with clinically suspected subarachnoid hemorrhage underwent both CTA-MMBE and DSA for diagnosis of an intracranial aneurysm. Two neuroradiologists, independently, evaluated 27 predefined vessel locations in the CTA-MMBE images for the presence of an aneurysm. After consensus, diagnostic accuracy of CTA was calculated per predefined location and per patient. Interobserver agreement was calculated with κ statistics.RESULTS: In 88 patients (81%), 117 aneurysms (82 ruptured, 35 unruptured) were present on DSA. CTA-MMBE detected all ruptured aneurysms except 1. Overall specificity, sensitivity, positive predictive value, and negative predictive value of CTA-MMBE were 0.99, 0.90, 0.98, and 0.95 per patient and 0.91, 1.00, 0.97, and 0.99 per location, respectively. Sensitivity was 0.99 for aneurysms ≥3 mm and 0.38 for aneurysms <3 mm. Interobserver agreement for aneurysm detection was excellent (κ value of 0.92 per location and 0.80 per patient).CONCLUSION: CTA-MMBE is accurate in detecting intracranial aneurysms in any projection without overprojecting bone. CTA-MMBE has limited sensitivity in detecting very small aneurysms. Our data suggest that DSA and 3DRA can be limited to the vessel harboring the ruptured aneurysm before endovascular treatment, after detection of a ruptured aneurysm with CTA.

In current clinical practice, CT angiography (CTA) is the most frequently used noninvasive diagnostic tool for detection of intracranial aneurysms in the acute setting.^1–8 However, detection of intracranial aneurysms by CTA is limited because axial source section evaluation is tedious and 3D visualization is hampered by overprojecting bone, especially in the region of the skull base.^2,9–13 Several methods to remove bone, such as subtraction and manual or automated bone editing, have been developed.^7,8,14–19 Drawbacks of these methods are the complexity of use, dependence on the user, or high dose of radiation.Matched mask bone elimination (MMBE) is a relatively new technique to remove bone from CTA source images (CTA-MMBE) in an automatic and user-independent way with little additional radiation dose.^20–22 In CTA-MMBE, a second nonenhanced low-dose scan (about a quarter of the radiation dose of a regular CTA) is used to identify bony structures that can subsequently be masked in the CTA scan.Digital subtraction angiography (DSA) is the gold standard for detection of intracranial aneurysms. Extension of DSA with 3D rotational angiography (3DRA) can further improve detection of intracranial aneurysms that may be obscured by overprojecting vessels.^23–25 The advantages of DSA over CTA are superior spatial and contrast resolution, no interference of bony structures, and the possibility to perform direct endovascular interventions.^26,27 However, DSA is an invasive technique with a small but significant risk of neurologic complications, estimated to occur in 0.3%–1.8% of patients.^28,29The purpose of this study was to determine the diagnostic accuracy of CTA-MMBE for detection of intracranial aneurysms in a large patient population with clinically suspected subarachnoid hemorrhage (SAH) with DSA and 3DRA as reference standards.     

Diffusion tensor MR imaging in chronic spinal cord injury

BACKGROUND AND PURPOSE: Diffusion tensor MR imaging is emerging as an important tool for displaying anatomic changes in the brain after injury or disease but has been less widely applied to disorders of the spinal cord. The aim of this study was to characterize the diffusion properties of the entire human spinal cord in vivo during the chronic stages of spinal cord injury (SCI). These data provide insight into the structural changes that occur as a result of long-term recovery from spinal trauma.MATERIALS AND METHODS: Thirteen neurologically intact subjects and 10 subjects with chronic SCI (>4 years postinjury) were enrolled in this study. A single-shot twice-refocused spin-echo diffusion-weighted echo-planar imaging pulse sequence was used to obtain axial images throughout the entire spinal cord (C1-L1) in <60 minutes.RESULTS: Despite heterogeneity in SCI lesion severity and location, diffusion characteristics of the chronic lesion were significantly elevated compared with those of uninjured controls. Fractional anisotropy was significantly lower at the chronic lesion and appeared dependent on the completeness of the injury. Conversely, mean diffusivity measurements in the upper cervical spinal cord in subjects with SCI were significantly lower than those in controls. These trends suggest that the entire neuraxis may be affected by long-term recovery from spinal trauma.CONCLUSION: These results suggest that diffusion tensor imaging may be useful in the assessment of SCI recovery.

Diffusion tensor imaging (DTI) has been successfully used to characterize structural changes in neural tissue after spinal artery stroke,¹ multiple sclerosis,^2,3 cervical spondylotic myelopathy,⁴ spinal cord compression,⁵ and acute spinal cord injury (SCI)^6,7; however, DTI has not been used to explore the long-term changes in spinal cord structure known to accompany chronic SCI.^8–11 The purpose of this study was to characterize the diffusion values of the entire spinal cord in humans with chronic SCI (>4 years postinjury) by using a clinically available pulse sequence and comparing these data with normative DTI characteristics reported previously.¹² On the basis of previous work,¹³ we hypothesized that diffusion characteristics would be significantly altered throughout the entire length of the spinal cord.DTI research in SCI largely involves the use of experimental animal models to examine changes in diffusivity that accompany the early stages of injury. These studies have suggested overall diffusivity increases and diffusion anisotropy decreases near the injury site^14–18 due to axonal damage and/or vasogenic edema.¹⁵ Although a few studies have been conducted with human spinal cord pathologies,^4–7,19 they have also demonstrated an increase in diffusivity and a decrease in diffusion anisotropy.DTI may be useful for identifying the characteristics of chronic SCI, because structural changes in the spinal cord during the chronic stages may differ from the normal spinal cord and the spinal cord in acute stages of injury. For example, extensive longitudinal spreading of lesions in the late stages of injury creates widespread changes in the spinal cord morphology, including cyst formation and necrosis.²⁰ Changes in diffusivity associated with these structural alterations may make it possible to identify the rostral and caudal extent of a spinal lesion by using DTI. Many therapeutic interventions for rehabilitation after SCI, including functional electric stimulation²¹ and gait training,²² rely on intact spinal motoneurons below the level of the lesion. Incomplete injury in segments below the injury may be particularly difficult to identify by using physical or electrophysiologic measurements because sensory and motor function is often reduced or absent below the level of injury. Thus, DTI provides an opportunity to assess the integrity of the spinal cord.DTI might also be sensitive to changes in the structure of the spinal cord tissue in regions distant from the spinal lesion in chronic injury. Although the chronic stages of SCI are typically considered stable,^23,24 progressive demyelination in chronic SCI has been documented,^8–10 and remyelination, when it occurs, can result in significantly decreased myelin sheath thickness^8,25–27 and preferential loss of large-diameter axons.²⁶ Also, considerable atrophy of the spinal cord occurs in the late stages of SCI, causing the remaining axons to be compressed and tightly packed.¹¹ These changes could increase the attenuation of diffusion barriers, which would be consistent with the decrease in mean diffusivity recently reported in the upper cervical spinal cord rostral to the injury in a small number of subjects with chronic SCI.¹³Thus, the primary aim of this study was to characterize the diffusion properties across the entire spinal cord (C1–L1 vertebral levels) in humans with chronic SCI by using a clinically available DTI pulse sequence. We then compared these data with diffusion characteristics from a previously published young neurologically intact sample.¹²     

The early evolution of spinal cord lesions on MR imaging following traumatic spinal cord injury

BACKGROUND AND PURPOSE: How early spinal cord injury (SCI) lesions evolve in patients after injury is unknown. The purpose of this study was to characterize the early evolution of spinal cord edema and hemorrhage on MR imaging after acute traumatic SCI.MATERIALS AND METHODS: We performed a retrospective analysis of 48 patients with clinically complete cervical spine injury. Inclusion criteria were the clear documentation of the time of injury and MR imaging before surgical intervention within 72 hours of injury. The length of intramedullary spinal cord edema and hemorrhage was assessed. The correlation between time to imaging and lesion size was determined by multiple regression analysis. Short-interval follow-up MR imaging was also available for a few patients (n = 5), which allowed the direct visualization of changes in spinal cord edema.RESULTS: MR imaging demonstrated cord edema in 100% of patients and cord hemorrhage in 67% of patients. The mean longitudinal length of cord edema was 10.3 ± 4.0 U, and the mean length of cord hemorrhage was 2.6 ± 2.0 U. Increased time to MR imaging correlated to increased spinal cord edema length (P = .002), even after accounting for the influence of other variables. A difference in time to MR imaging of 1.2 days corresponded to an average increase in cord edema by 1 full vertebral level. Hemorrhage length was not affected by time to imaging (P = .825). A temporal increase in the length of spinal cord edema was confirmed in patients with short-interval follow-up MR imaging (P = .003).CONCLUSION: Spinal cord edema increases significantly during the early time period after injury, whereas intramedullary hemorrhage is comparatively static.

Acute traumatic spinal cord injury (SCI) is a devastating event with an incidence of approximately 11,000 injuries in the United States each year.¹ MR imaging is critical to the assessment of acute cervical SCI because it clearly depicts lesion location, extent, and severity. Spinal cord intramedullary edema and hemorrhage are readily appreciated^2,3 and, to some extent, correlate with the clinical neurologic deficit.^4–10 Prior studies have also revealed that both the presence of hemorrhage and increased hematoma length at MR imaging are associated with decreased motor recovery.^7–10Following the immediate structural and neurovascular insult, acute SCI sets into motion a cascade of secondary injuries.^11,12 Work in animals has shown that intramedullary spinal cord hemorrhage and edema are dynamic, whether assessed by histopathology or MR imaging.^13,14The extent to which cord lesions evolve in patients during the early phase of SCI (ie, the first hours and days postinjury) is unknown; therefore, given similar clinical deficits, it is unclear to what extent variability in lesion size reflects differences in time to imaging after trauma. Similarly, it is not clear whether lesion expansion when observed on a short-interval follow-up MR imaging study is an ominous sign or a usual feature in the natural evolution of SCI. This fundamental lack of knowledge is particularly limiting with regard to research aimed at preventing the secondary injury cascade. With an increasing number of therapies for SCI coming to trial, MR imaging can be expected to continue to be increasingly incorporated into research protocols for these agents. An understanding of the acute evolution of SCI lesions on MR imaging is essential if imaging is to be used effectively in these protocols. Additionally, the variability of SCI lesions with time, if demonstrated, would likely have a significant impact on efforts to correlate spinal cord lesion size and location to the neurologic level of injury, because prior studies have not systematically accounted for differences in time to imaging. Such variability currently limits the reliability of MR imaging to serve as an accurate predictor of the patient''s neurologic level and prognosis. This limitation is unfortunate in situations in which the MR imaging findings might be of particular utility, such as in the assessment of the obtunded patients or in patients not undergoing clinical evaluation at a specialized SCI center.To better understand the evolution of SCI lesions, we retrospectively studied how the time interval between trauma and MR imaging affects spinal cord lesion size in patients with similar neurologic deficits. We also directly measured cord edema changes in a small number of patients for whom short-term MR imaging follow-up was available.     

MR imaging: influence of imaging technique and postprocessing on measurement of internal carotid artery stenosis

BACKGROUND AND PURPOSE: MR angiography (MRA) is increasingly used as an alternative to digital subtraction angiography (DSA) to evaluate internal carotid artery (ICA) stenosis. Because MRA is not standardized in data acquisition and postprocessing, we sought to evaluate the effects of different acquisition techniques (time-of-flight MRA [TOF-MRA]) and contrast-enhanced MRA [CE-MRA]) and postprocessing methods (maximum intensity projection [MIP], multiplanar reformation [MPR], and volume-rendering on stenosis grading.MATERIALS AND METHODS: Fifty patients (33 men, 17 women) with symptomatic ICA stenosis were examined at 1.5T. Two imaging techniques and 3 postprocessing methods resulted in 6 image datasets per patient. Two readers independently evaluated ICA stenosis according to the North American Symptomatic Carotid Endarterectomy Trial criteria. Interobserver variability was calculated with the Pearson correlation coefficient and simultaneous confidence intervals (CI). The relationship of the values of ICA stenosis between the techniques was assessed by means of simultaneous 95% Tukey CI.RESULTS: Interobserver agreement was high. Higher concordance was found for postprocessing techniques with TOF- than with CE-MRA; the mean difference between TOF-MPR and TOF-MIP was 0.4% (95% CI, −2.9%–3.8%). Stenosis values for CE-MPR differed significantly from those of CE volume-rendering (7.2%; 95% CI, 3.9%–10.6%).CONCLUSION: Stenosis grading was found to be independent of the postprocessing technique except for comparison of CE-MPR with CE volume-rendering, with the volume-rendering technique resulting in higher stenosis values. MPR seems to be best-suited for measurement of ICA stenosis. Parameter setting is critical with volume-rendering, in which stenosis values were consistently higher compared with the other methods.

In large clinical trials like the North American Symptomatic Carotid Endarterectomy Trial, the European Carotid Surgery Trial, or the Asymptomatic Carotid Atherosclerosis Study, therapeutic decisions were based on the degree of internal carotid artery (ICA) stenosis determined with digital subtraction angiography (DSA).^1–4 DSA is still regarded as the gold standard because it provides the highest spatial resolution and dynamic information. On the other hand, the procedure is expensive^5,6 and associated with neurologic complications.^7–9MR angiography (MRA) offers multiple projections, 3D depiction of vessels, and cross-sectional images for the exact measurement of the stenotic lumen and might replace intra-arterial carotid angiography for the measurement of ICA stenosis.¹⁰MRA is increasingly used as a confirmatory examination in patients presenting with either symptomatic or asymptomatic atherosclerotic disease of the ICA after undergoing Doppler sonography. Frequently patients scheduled for intervention (surgery or stent placement) present with MRA examinations performed at other institutions or imaging centers, bringing along either CD-ROMs including source images as well as maximum intensity projection (MIP), multiplanar reformation (MPR), or volume-rendering studies or only hard copies (film or paper) with postprocessed MRA studies. Contrast enhanced MRA (CE-MRA) is the predominant technique due to larger volume coverage and shorter examination time. On the other hand, non-CE techniques like 3D time-of-flight MRA (3D-TOF-MRA) are having a renaissance because of an increasing number of reports about the adverse effects of gadolinium, especially nephrogenic systemic fibrosis in patients with renal impairment.¹¹The aim of our study was to compare different imaging techniques (CE-MRA, TOF-MRA) and postprocessing methods (MPR, MIP, volume-rendering) to detect significant differences in stenosis measurement between the imaging techniques or postprocessing methods.     

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.     

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.     

Assessment of the language laterality index in patients with brain tumor using functional MR imaging: effects of thresholding, task selection, and prior surgery

BACKGROUND AND PURPOSE: Functional MR imaging (fMRI) is used to determine preoperatively the laterality of cortical language representation along with the relationship of language areas to adjacent brain tumors. The purpose of this study was to determine whether changing the statistical threshold for different language tasks influences the language laterality index (LI) for a group of controls, patients with tumor without prior surgery, and patients with tumor and prior surgery.MATERIALS AND METHODS: Seven controls, 9 patients with tumor without prior surgery, and 4 patients with tumor and prior surgery performed verb-generation, phonemic fluency, and semantic fluency language tasks during fMRI. Interhemispheric activation differences between the left and right Broca regions of interest were determined by calculating language LIs. LIs were compared within each group, between groups, and between language tasks. Intraoperative electrocortical mapping or the presence of aphasia during postoperative neurology examinations or both were used as ground truth.RESULTS: The language LI varied as a result of statistical thresholding, presence of tumor, prior surgery, and language task. Although patients and controls followed a similar shape in the LI curve, there was no optimal P value for determining the LI. Three patients demonstrated a shift in the LI between hemispheres as a function of statistical threshold. Verb generation was the least variable task both between tasks and across groups.CONCLUSION: For preoperative patients with tumor, the LI should be examined across a spectrum of P values and a range of tasks to ensure reliability. Our data suggest that the LI may be threshold- and task-dependent, particularly in the presence of adjacent tumor.

Quality of life is an important factor in the decision to undergo neurosurgery. The ability to produce and comprehend language is a significant part of postoperative quality of life. Therefore, the potential of losing language function postoperatively may preclude surgical resection of a tumor.The preoperative assessment of language localization can be useful in planning surgical resection and deciding whether to perform awake cortical mapping. To this end, functional MR imaging (fMRI) has been used to determine the areas of the cortex involved in language functioning in preoperative patients with tumor.^1–5 fMRI is noninvasive and repeatable; and by showing the relationship between functional language cortex and a tumor, it may tailor a surgeon''s approach to the tumor. Currently, intraoperative cortical mapping remains the gold standard for localizing language in patients with tumor, and several studies have demonstrated significant concordance between fMRI and intraoperative electrocorticography.^1,6–9 Additionally, fMRI may reduce overall surgical time by guiding direct cortical stimulation and is particularly useful in cases in which the awake mapping procedure fails due to seizures or issues with the patient''s tolerance for anesthesia.The language laterality index (LI) is a ratio measure using the number of active fMRI voxels that determines hemispheric dominance for language and has been used to determine surgical candidacy for patients with brain tumor.^7,10–14 One potential issue with the LI calculations in fMRI is that the specificity and sensitivity to true neural activity change with the application of different statistical thresholds. As a result, it is expected that language dominance as measured by the LI will vary as the statistical confidence threshold is changed. Theoretically, it is possible for the LI to transfer from 1 hemisphere to the other, depending on the threshold chosen. It has been shown in control subjects that the LI strengthens toward the dominant hemisphere as the statistical threshold increases.¹² No prior studies have examined the LI across a spectrum of P values in patients with tumor. This issue is especially important in evaluating preoperative patients for whom the determination of language dominance is relevant to surgical planning.Using fMRI in patients with tumor presents unique challenges. First, prior studies in angiography and MR imaging have shown that vessels within a glioma lose their ability to autoregulate normally.^15–17 This, in turn, may limit the ability of the blood oxygen level–dependent (BOLD) signal intensity to detect true neural activity in patients with tumor. Previous studies have shown that the volume of BOLD activation is significantly reduced in the tumor hemisphere in comparison with the contralateral control hemisphere in the motor strip.^18–21 Second, the mass effect of large tumors may affect the blood flow of adjacent circulation by compressing veins, thereby causing oxygenated blood to drain from the activated region more quickly, possibly truncating the BOLD signal intensity.^22,23 Finally, susceptibility artifacts from surgical staples, metal used to secure skull flaps, and blood products may also compromise the detection of the BOLD signal intensity, given prior neurosurgery.²⁴In addition to physiologic and technical parameters affecting the measure of laterality, studies suggest that the degree of lateralization may depend on the language task.^7,9,25 In general, paradigms such as verb generation tend to lateralize language better than paradigms like picture naming.^7,11 The verb-generation task has shown the most concordance with intraoperative mapping overall.^7,12,26Accordingly, the goal of our study was multifactorial. We aimed to characterize the LIs measured over a range of statistical thresholds in control subjects and in patients with brain tumors, and we compared the relative distribution of fMRI activity seen by using several paradigms known to lateralize language. We predicted that laterality indices would be more variable in patients with tumor than in control subjects and that the verb-generation paradigm would most consistently lateralize language across groups.     

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.     

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.