Correlation of Prenatal and Postnatal MRI Findings in Schizencephaly

BACKGROUND AND PURPOSE:Schizencephaly is a rare malformation of the brain characterized by a gray matter–lined defect extending from the pial surface to the lateral ventricles. The purpose of this study was to correlate imaging findings of schizencephaly and associated anomalies on fetal and postnatal MR imaging and assess possible changes that may occur from the prenatal-to-postnatal state.MATERIALS AND METHODS:A retrospective review of subjects with schizencephaly who had both pre- and postnatal MR imaging was performed. Subject age, cleft type, number, location, and features of the defects and associated anomalies were recorded. Normalized dimensions of the defect and ipsilateral ventricle were measured and correlated to changes in the clefts between pre- and postnatal imaging.RESULTS:Ten subjects with 18 clefts (8 bilateral) were included. Most defects (83%) were open on prenatal MR imaging, but 47% of those were found to have subsequently closed on postnatal imaging. Evidence of prior hemorrhage was seen in 83%. Prenatal MR imaging detected all cases of an absent septum pellucidum but detected a fraction of gross polymicrogyria and missed all cases of optic nerve hypoplasia. The normalized ipsilateral ventricular and inner and middle width dimensions of the defects were significantly decreased at postnatal imaging (P < .05). The widths of the defects, ventricular width, and presence of hemorrhage were not predictors of closure of prenatally diagnosed open defects (P > .05).CONCLUSIONS:In our series, nearly half of prenatally open schizencephaly defects had closed on postnatal imaging. Prenatal MR imaging was only able to demonstrate some of the associated anomalies.

Schizencephaly is a rare malformation of the central nervous system characterized by a gray matter–lined defect extending from the pial surface to the lateral ventricles. The etiology of schizencephaly is poorly understood; however, it appears to be heterogeneous.^1–3 The presence of gray matter lining the defects, distinguishing schizencephaly from porencephaly, is usually ascribed to the damage to the radial glial cell fibers or to the molecules that promote neuronal migration and timing during pregnancy.^2,4 Despite early reports of the association of schizencephaly and mutations of the EMX2 homeobox gene,⁵ this association has not been verified in further studies.⁶ The common pathophysiology of injury is frequently ascribed to a vascular disruption, hypoxia-ischemia, and/or prenatal infection at critical time points during neuronal development,^1–3 though there are some reports favoring schizencephaly as a developmental disorder.^7–9Classically, schizencephaly has been divided into “closed” or “closed-lip” defects, in which the walls appose one another within the defect, and “open” or “open-lip” defects, in which CSF fills the defect all the way from the lateral ventricle to the overlying subarachnoid space.¹⁰ Open lesions have been further subclassified as small or large according to size of the defect.¹⁰ These classifications have prognostic significance because it has been shown that a small, unilateral closed defect without involvement of the motor cortex can be associated with seizures but otherwise normal development.¹⁰ The prognosis is poorer with open and bilateral defects.^2,10,11 Associated anomalies, such as optic nerve hypoplasia, absence of the septum pellucidum, and other migrational abnormalities, will also adversely affect the prognosis.^2,9,12,13MR imaging was reported to prenatally diagnose schizencephaly as early as 1989.¹⁴ On the basis of the current literature, the imaging appearance of schizencephaly on fetal MR imaging is considered identical to that in postnatal MR imaging.² The purpose of this study was to correlate imaging findings of schizencephaly and associated anomalies on fetal and postnatal MR imaging and to assess the possible changes that may occur from the prenatal-to-postnatal state on MR imaging.     

Prenatal Diagnosis of Fetal Ventriculomegaly: Agreement between Fetal Brain Ultrasonography and MR Imaging

BACKGROUND AND PURPOSE:Accurate measurement of the lateral ventricles is of paramount importance in prenatal diagnosis. Possible conflicting classifications caused by their measurement in different sectional planes by sonography and MR imaging are frequently raised. The objective of our study was to evaluate the agreement between ultrasonography and MR imaging in the measurement of the lateral ventricle diameter in the customary sectional planes for each technique.MATERIALS AND METHODS:Measurement of both lateral ventricles was performed prospectively in 162 fetuses from 21 to 40 weeks of gestational age referred for evaluation due to increased risk for cerebral pathology. The mean gestational age for evaluation was 32 weeks. The measurements were performed in the customary plane for each technique: axial plane for sonography and coronal plane for MR imaging.RESULTS:The 2 techniques yielded results in substantial agreement by using intraclass correlation and κ coefficient score tests. When we assessed the clinical cutoff of 10 mm, the κ score was 0.94 for the narrower ventricle and 0.84 for the wider ventricle, expressing almost perfect agreement. The Bland-Altman plot did not show any trend regarding the actual width of the ventricle, gestational week, or interval between tests. Findings were independent for fetal position, sex, and indication for examination.CONCLUSIONS:Our study indicates excellent agreement between fetal brain ultrasonography and MR imaging as to the diagnosis of fetal ventriculomegaly in the customarily used sectional planes of each technique.

Ventricular dilation is one of the most common, prenatally diagnosed cerebral abnormalities.^1,2 “Ventriculomegaly” is defined as an atrial diameter exceeding 10 mm.^3,4 The prognosis of ventricular dilation depends on the degree of dilation and the presence of associated cerebral or extracerebral abnormalities.⁵ Thus, accurate measurement of the lateral ventricles is of paramount importance in prenatal diagnosis. Recently, guidelines for the assessment of the diameter of the lateral ventricles by using the axial transventricular plane as part of routine fetal sonographic evaluation have been suggested.^6,7MR imaging of the fetal CNS is a complementary tool and is performed following detection of abnormalities identified by sonography. The common belief is that fetal CNS MR imaging is more accurate than sonography, particularly when evaluation for associated anomalies is required, when the mother is obese, or when more precise measurement of the ventricular diameter is required.⁸Measurement of lateral ventricle diameter by using MR imaging is performed on a coronal plane.⁹ Measurement of lateral ventricle diameter by using ultrasound is performed on an axial plane.⁶ This variation may raise possible conflicting classifications due to different sectional planes or use of different tools. The aim of our study was to evaluate the agreement between ultrasonography and MR imaging in the measurement of the lateral ventricle diameter in the customary sectional planes for each technique in prenatal diagnosis.     

Apparent Diffusion Coefficient Value Changes and Clinical Correlation in 90 Cases of Cytomegalovirus-Infected Fetuses with Unremarkable Fetal MRI Results

BACKGROUND AND PURPOSE:Cytomegalovirus is the leading intrauterine infection. Fetal MR imaging is an accepted tool for fetal brain evaluation, yet it still lacks the ability to accurately predict the extent of the neurodevelopmental impairment, especially in fetal MR imaging scans with unremarkable findings. Our hypothesis was that intrauterine cytomegalovirus infection causes diffusional changes in fetal brains and that those changes may correlate with the severity of neurodevelopmental deficiencies.MATERIALS AND METHODS:A retrospective analysis was performed on 90 fetal MR imaging scans of cytomegalovirus-infected fetuses with unremarkable results and compared with a matched gestational age control group of 68 fetal head MR imaging scans. ADC values were measured and averaged in the frontal, parietal, occipital, and temporal lobes; basal ganglia; thalamus; and pons. For neurocognitive assessment, the Vineland Adaptive Behavior Scales, Second Edition (VABS-II) was used on 58 children in the cytomegalovirus-infected group.RESULTS:ADC values were reduced for the cytomegalovirus-infected fetuses in most brain areas studied. The VABS-II showed no trend for the major domains or the composite score of the VABS-II for the cytomegalovirus-infected children compared with the healthy population distribution. Some subdomains showed an association between ADC values and VABS-II scores.CONCLUSIONS:Cytomegalovirus infection causes diffuse reduction in ADC values in the fetal brain even in unremarkable fetal MR imaging scans. Cytomegalovirus-infected children with unremarkable fetal MR imaging scans do not deviate from the healthy population in the VABS-II neurocognitive assessment. ADC values were not correlated with VABS-II scores. However, the lack of clinical findings, as seen in most cytomegalovirus-infected fetuses, does not eliminate the possibility of future neurodevelopmental pathology.

Cytomegalovirus (CMV) infection is the most common intrauterine infection, with an overall birth prevalence of 1% (range, 0.2%–2.5%).^1,2 Only 10%–15% of the infected fetuses are symptomatic at birth, presenting with typical clinical findings of congenital infection,^3,4 while an additional 10%–15% of infants develop the symptoms during the first years of life.^1,2,5,6 The clinical findings include, but are not limited to, intrauterine growth restriction, periventricular calcifications, microcephaly, ventriculomegaly, hepatosplenomegaly, and cardiovascular system anomalies.^3,4,7Most symptomatic infants will have long-term sequelae, including neurodevelopmental damage with intellectual disabilities, ranging up to severe decreases in cognitive capacity.^2,4,5,8,9 Asymptomatic neonates constitute most cases, up to 90% of the infected fetuses, with outcomes still unclear due to limited research.^1,5,6,8,9Sonography is a widely used prenatal screening tool and can show typical findings suggestive of CMV infection. Recent studies have shown that sonography is not sensitive enough for the entire spectrum of neuropathologies, mainly brain maturation.^10,11 Fetal head MR imaging (feMRI) is accepted as a complementary test for the evaluation of the brain. Studies have shown that feMRI produces much more information, including improved spatial resolution, visualization of the entire brain parenchyma, and detection of white matter maturation and pathologies earlier and better than sonography.^10–13 However, even with both techniques combined, it is still unclear how to accurately predict the extent of the neurodevelopmental impairment in the prenatal period, especially in cases without any notable imaging pathology.^10,11,13,14Diffusion-weighted imaging (DWI, DTI) was studied extensively for its utility in the evaluation of the normal development of the fetal brain.^15–20 One of the DWI metrics, the apparent diffusion coefficient, allows quantitative evaluation of cerebral maturation and intracellular changes in utero.^15,18–22 Very little research has been done examining the ADC values in CMV-infected fetal brains, and even less research has focused on fetuses with normal feMRI results.^14,18In our current study, we compared ADC values in several anatomic brain areas of CMV-infected fetuses with unremarkable feMRI results and an age-matched control group with normal MR imaging findings. For neurodevelopmental assessment, the Vineland Adaptive Behavior Scales, Second Edition (VABS-II)^23,24 was performed on children from the CMV-infected group.Our hypothesis was that CMV-infection causes diffusional changes in fetal brains and that those changes may be correlated to the severity of neurodevelopmental deficiencies.     

Parent Artery Curvature Influences Inflow Zone Location of Unruptured Sidewall Internal Carotid Artery Aneurysms

BACKGROUND AND PURPOSE:Future aneurysmal behaviors or treatment outcomes of cerebral aneurysms may be related to the hemodynamics around the inflow zone. Here we investigated the influence of parent artery curvature on the inflow zone location of unruptured sidewall internal carotid artery aneurysms.MATERIALS AND METHODS:In 32 aneurysms, the inflow zone location was decided by 4D flow MR imaging, and the radius of the parent artery curvature was measured in 2D on an en face image of the section plane corresponding to the aneurysm orifice.RESULTS:The inflow zone was on the distal neck in 10 (group 1, 31.3%), on the lateral side in 19 (group 2, 59.4%), and on the proximal neck in 3 (group 3, 9.4%) aneurysms. The radius in group 1 was significantly larger than that in group 2 (8.3 mm [4.5 mm] versus 4.5 mm [1.9 mm]; median [interquartile range]; P < .0001). All 7 aneurysms with a radius of >8.0 mm were in group 1. All 18 aneurysms with a radius of <6.0 mm were in group 2 or 3. In two group 3 aneurysms, the inflow zone was located in a part of the neck extending beyond the central axis of the parent artery.CONCLUSIONS:The inflow zone locations of sidewall aneurysms can be influenced by the parent artery curvature evaluated in 2D on an en face image of the section plane corresponding to the aneurysm orifice.

The hemodynamics around the inflow zone of cerebral aneurysms may be a principal cause of growth,^1–4 bleb formation resulting in rupture,^1,2,5–8 and regrowth following clipping surgery or endovascular coiling.^9–13 These sequelae are possibly related to the increased wall shear stress on the aneurysmal wall surrounding the inflow zone.^2–6,14 Therefore, both identification of the exact location of the inflow zone and evaluation of the hemodynamics around this area may contribute to predicting future aneurysmal behaviors or obtaining good treatment outcomes.¹⁵ Previous studies have estimated that neck width and geometric relationship between an aneurysm and the parent artery are dominant factors in the determination of the inflow zone location.^1,14,16–194D flow MR imaging based on time-resolved 3D cine phase-contrast MR imaging techniques was recently used to evaluate the hemodynamics of cerebral aneurysms^20–24 and to identify the inflow zone of cerebral aneurysms.¹⁵ However, no previous studies have examined the correlation between the distribution of the inflow zone on the section plane corresponding to the aneurysm orifice and aneurysm morphology or the parent artery curvature in patient-specific imaging analysis, to our knowledge. Here we investigated the influence of morphologic factors or the parent artery curvature on the inflow zone location identified by using 4D flow MR imaging in unruptured sidewall ICA aneurysms.     

Imaging Findings in MR Imaging–Guided Focused Ultrasound Treatment for Patients with Essential Tremor

BACKGROUND AND PURPOSE:MR imaging–guided focused sonography surgery is a new stereotactic technique that uses high-intensity focused sonography to heat and ablate tissue. The goal of this study was to describe MR imaging findings pre- and post-ventralis intermedius nucleus lesioning by MR imaging–guided focused sonography as a treatment for essential tremor and to determine whether there was an association between these imaging features and the clinical response to MR imaging–guided focused sonography.MATERIALS AND METHODS:Fifteen patients with medication-refractory essential tremor prospectively gave consent; were enrolled in a single-site, FDA-approved pilot clinical trial; and were treated with transcranial MR imaging–guided focused sonography. MR imaging studies were obtained on a 3T scanner before the procedure and 24 hours, 1 week, 1 month, and 3 months following the procedure.RESULTS:On T2-weighted imaging, 3 time-dependent concentric zones were seen at the site of the focal spot. The inner 2 zones showed reduced ADC values at 24 hours in all patients except one. Diffusion had pseudonormalized by 1 month in all patients, when the cavity collapsed. Very mild postcontrast enhancement was seen at 24 hours and again at 1 month after MR imaging–guided focused sonography. The total lesion size and clinical response evolved inversely compared with each other (coefficient of correlation = 0.29, P value = .02).CONCLUSIONS:MR imaging–guided focused sonography can accurately ablate a precisely delineated target, with typical imaging findings seen in the days, weeks, and months following the treatment. Tremor control was optimal early when the lesion size and perilesional edema were maximal and was less later when the perilesional edema had resolved.

MR imaging–guided focused sonography surgery is a new stereotactic technique that uses high-intensity focused sonography to heat and ablate tissue rapidly under closed-loop image guidance and control throughout all steps of the intervention process. MR imaging allows precise intraprocedural localization of the ablation target, verification of safety margins for the sonography treatment, and real-time monitoring of thermal ablation dynamics.^1–7 MR imaging–guided focused sonography is now accepted in the treatment of soft-tissue disorders, including prostate cancer and uterine fibroids. Intracranial applications for brain tumors^8,9 and neuropathic pain syndromes^10,11 are currently under investigation. More recently, MR imaging–guided focused sonography was tested in a clinical trial as a treatment for essential tremor.Essential tremor is a common and disabling movement disorder with an estimated prevalence of 0.3%–5.55%.^12–17 Patients with essential tremor may suffer more from the mental effects on quality of life, such as lower perceived health status,¹⁸ than from actual physical symptoms.¹⁹ Essential tremor may be medically refractory: up to 30% of patients do not respond to first-line therapy and may consider surgical options.²⁰ Improved imaging and refined electrophysiologic localization have demonstrated that the ventralis intermedius nucleus (Vim) of the thalamus is the most effective target. The ventralis intermedius nucleus was the target for the MR imaging–guided focused sonography treatment in the clinical trial mentioned above.The goal of this study was to describe findings on MR imaging both pre- and post-Vim lesioning by MR imaging–guided focused sonography as a treatment for essential tremor in the 15 patients enrolled in the trial and to determine whether there was an association between these imaging features, the number and/or energy of sonications, and the clinical response to MR imaging–guided focused sonography.     

Brain Parenchymal Signal Abnormalities Associated with Developmental Venous Anomalies in Children and Young Adults

BACKGROUND AND PURPOSE:Abnormal signal in the drainage territory of developmental venous anomalies has been well described in adults but has been incompletely investigated in children. This study was performed to evaluate the prevalence of brain parenchymal abnormalities subjacent to developmental venous anomalies in children and young adults, correlating with subject age and developmental venous anomaly morphology and location.MATERIALS AND METHODS:Two hundred eighty-five patients with developmental venous anomalies identified on brain MR imaging with contrast, performed from November 2008 through November 2012, composed the study group. Data were collected for the following explanatory variables: subject demographics, developmental venous anomaly location, morphology, and associated parenchymal abnormalities. Associations between these variables and the presence of parenchymal signal abnormalities (response variable) were then determined.RESULTS:Of the 285 subjects identified, 172 met inclusion criteria, and among these subjects, 193 developmental venous anomalies were identified. Twenty-six (13.5%) of the 193 developmental venous anomalies had associated signal-intensity abnormalities in their drainage territory. After excluding developmental venous anomalies with coexisting cavernous malformations, we obtained an adjusted prevalence of 21/181 (11.6%) for associated signal-intensity abnormalities in developmental venous anomalies. Signal-intensity abnormalities were independently associated with younger subject age, cavernous malformations, parenchymal atrophy, and deep venous drainage of developmental venous anomalies.CONCLUSIONS:Signal-intensity abnormalities detectable by standard clinical MR images were identified in 11.6% of consecutively identified developmental venous anomalies. Signal abnormalities are more common in developmental venous anomalies with deep venous drainage, associated cavernous malformation and parenchymal atrophy, and younger subject age. The pathophysiology of these signal-intensity abnormalities remains unclear but may represent effects of delayed myelination and/or alterations in venous flow within the developmental venous anomaly drainage territory.

Developmental venous anomalies (DVAs) are frequently identified on routine MR imaging of the brain with contrast. DVAs are typically considered normal variants of venous development and usually have no associated imaging findings. However, a subset of DVAs has been associated with findings such as cavernous malformations (CMs),^1–3 thrombosis with subsequent venous infarction,^4–8 lobar atrophy,⁹ T2 and FLAIR signal-intensity abnormalities,^9,10 and SWI hypointensities.¹¹ Signal abnormalities can occur in the drainage territory of DVAs and may produce diagnostic uncertainty with regard to the significance and relationship to presenting symptoms. Signal abnormalities on MR imaging have been described in 12.5%¹⁰ to 28.3%⁹ of DVAs in adults, with an increasing prevalence with older age. While well described in adults, this relationship has not been investigated in children, to our knowledge. The MR imaging appearance of the brain in children is quite different from that in adults during myelination, and the effect of DVAs on regional brain maturation has not been studied.The most commonly proposed etiologies for parenchymal abnormalities associated with DVAs are chronic venous hypertension/insufficiency leading to ischemia or microhemorrhage.^9–12 Although the effect of brain maturation is unknown, on the basis of these pathophysiologic mechanisms, we hypothesized that parenchymal abnormalities would be less common in children compared with adults. This study was performed to test this hypothesis and to investigate clinical factors and DVA characteristics associated with parenchymal signal abnormalities in children and young adults.     

Development of the Fetal Vermis: New Biometry Reference Data and Comparison of 3 Diagnostic Modalities–3D Ultrasound, 2D Ultrasound,and MR Imaging

BACKGROUND AND PURPOSE:Normal biometry of the fetal posterior fossa rules out most major anomalies of the cerebellum and vermis. Our aim was to provide new reference data of the fetal vermis in 4 biometric parameters by using 3 imaging modalities, 2D ultrasound, 3D ultrasound, and MR imaging, and to assess the relation among these modalities.MATERIALS AND METHODS:A retrospective study was conducted between June 2011 and June 2013. Three different imaging modalities were used to measure vermis biometry: 2D ultrasound, 3D ultrasound, and MR imaging. The vermian parameters evaluated were the maximum superoinferior diameter, maximum anteroposterior diameter, the perimeter, and the surface area. Statistical analysis was performed to calculate centiles for gestational age and to assess the agreement among the 3 imaging modalities.RESULTS:The number of fetuses in the study group was 193, 172, and 151 for 2D ultrasound, 3D ultrasound, and MR imaging, respectively. The mean and median gestational ages were 29.1 weeks, 29.5 weeks (range, 21–35 weeks); 28.2 weeks, 29.05 weeks (range, 21–35 weeks); and 32.1 weeks, 32.6 weeks (range, 27–35 weeks) for 2D ultrasound, 3D ultrasound, and MR imaging, respectively. In all 3 modalities, the biometric measurements of the vermis have shown a linear growth with gestational age. For all 4 biometric parameters, the lowest results were those measured by MR imaging, while the highest results were measured by 3D ultrasound. The inter- and intraobserver agreement was excellent for all measures and all imaging modalities. Limits of agreement were considered acceptable for clinical purposes for all parameters, with excellent or substantial agreement defined by the intraclass correlation coefficient.CONCLUSIONS:Imaging technique–specific reference data should be used for the assessment of the fetal vermis in pregnancy.

Imaging of the fetal posterior fossa is considered a routine part of the fetal sonographic examination. Normal sonographic biometry and normal morphology of the posterior fossa rule out most major anomalies of the fetal cerebellum and vermis.¹ However, in case of an abnormal posterior fossa, evaluation of the vermian biometry and morphology is of paramount importance, considering the wide clinical spectrum of this imaging finding.²Fetal posterior fossa anomalies range from benign asymptomatic conditions to severe abnormalities associated with neurologic impairment.^3–6 The most frequent of these anomalies, Blakes pouch cyst, vermian hypoplasia, and Dandy-Walker malformation, have a similar imaging appearance^7,8 but different vermian biometry and, therefore, different prognoses.⁹Many anomalies of the posterior fossa can be depicted with sonography alone.¹⁰ Although the standard axial imaging planes may detect most anomalies of the posterior fossa, the diagnosis of the exact type of abnormality might be challenging because a clear visualization of the midsagittal plane is essential. Subtle changes in the morphology of the vermis are hidden by this axial view, and this feature can lead to false-positive diagnoses of vermian pathologies.^11,12Our group has proposed using the transabdominal sagittal plane for visualization of the fetal vermis,¹³ while Malinger et al¹⁴ reported their experience with the transvaginal approach. Vinals et al¹⁵ used volume contrast imaging (VCI) on plane C to construct nomograms for the normal fetal vermis. Our group used this same VCI on plane C technique to compare normal and abnormal fetal vermis measurements, and we concluded that the 3D sonographic technique has many advantages in the detection of posterior fossa anomalies.¹⁶ It allows off-line evaluation and reconstruction of images, even with abnormal angles when the midsagittal plane is difficult to obtain.MR imaging is a well-known complementary tool in the prenatal diagnosis of fetal brain abnormalities. The challenges described above in achieving a good visualization of the midsagittal plane in prenatal sonography led to frequent use of this tool to assess, more accurately, the structures of the posterior fossa and improve prenatal diagnosis.Various nomograms have been developed to establish normal biometric measures of the fetal vermis by using ultrasound (US) or MR imaging.^17–19 None of these nomograms provided data regarding all 4 vermian biometric parameters. Moreover, there were no comparisons among all 3 imaging modalities.²⁰The aims of our study were the following: to provide normal reference biometric data of the fetal vermis in 4 biometric parameters for 3 imaging modalities, to evaluate the reproducibility of the vermian biometry, and to compare the measurements obtained by 2D sonography, 3D sonography, and MR imaging.     

3T Intraoperative MRI for Management of Pediatric CNS Neoplasms

BACKGROUND AND PURPOSE:High-field-strength intraoperative MR imaging has emerged as a powerful adjunct for resection of brain tumors. However, its exact role has not been firmly established. We sought to determine the impact of 3T-intraoperative MRI on the surgical management of childhood CNS tumors.MATERIALS AND METHODS:We evaluated patient data from a single academic children''s hospital during a consecutive 24-month period after installation of a 3T-intraoperative MRI. Tumor location, histology, surgical approach, operating room time, presence and volume of residual tumor, need for tumor and non-tumor-related reoperation, and anesthesia- and MR imaging–related complications were evaluated. Comparison with pre-intraoperative MRI controls was performed.RESULTS:One hundred ninety-four patients underwent intraoperative MRI–guided surgery. Of these, 168 were 18 years or younger (mean, 8.9 ± 5.0 years; 108 males/60 females). There were 65 posterior fossa tumors. The most common tumors were pilocytic astrocytoma (n = 31, 19%), low-grade glioma (n = 31, 19%), and medulloblastoma (n = 20, 12%). An average of 1.2 scanning sessions was performed per patient (maximum, 3). There were no MR imaging–related safety issues. Additional tumor was resected after scanning in 21% of patients. Among patients with a preoperative goal of gross total resection, 93% achieved this goal. The 30-day reoperation rate was <1% (n = 1), and no patient required additional postoperative MR imaging during the same hospital stay.CONCLUSIONS:Intraoperative MRI is safe and increases the likelihood of gross total resection, albeit with increased operating room time, and reduces the need for early reoperation or repeat sedation for postoperative scans in children with brain tumors.

Brain tumors are the second most common type of pediatric cancer, affecting more than 4000 children per year in the United States.¹ For many tumors, such as ependymoma and medulloblastoma, maximal cytoreductive resection offers the greatest chance for long-term survival.² Intraoperative MR imaging (iMRI) has been proposed as an adjunctive technique to achieve maximal tumor resection while limiting iatrogenic neurologic injury.^3–11 However, the benefits of this expensive technology have not been uniformly demonstrated in the literature.^11–14 With respect to high-field-strength iMRI, typically defined as 1.5T or higher, its impact on operating room and anesthesia time and the incidence of MR imaging–related complications, particularly in the pediatric population, have been the topic of limited publications.^3,15–17 We performed a retrospective review of our 24-month experience with a 3T-iMRI at a tertiary care children''s hospital to determine the impact of this tool on surgical planning, workflow, and patient outcomes. Comparison was made with a cohort of pediatric patients with brain tumor at our institution from before installation of the iMRI scanner.     

MR Elastography Can Be Used to Measure Brain Stiffness Changes as a Result of Altered Cranial Venous Drainage During Jugular Compression

BACKGROUND AND PURPOSE:Compressing the internal jugular veins can reverse ventriculomegaly in the syndrome of inappropriately low pressure acute hydrocephalus, and it has been suggested that this works by “stiffening” the brain tissue. Jugular compression may also alter blood and CSF flow in other conditions. We aimed to understand the effect of jugular compression on brain tissue stiffness and CSF flow.MATERIALS AND METHODS:The head and neck of 9 healthy volunteers were studied with and without jugular compression. Brain stiffness (shear modulus) was measured by using MR elastography. Phase-contrast MR imaging was used to measure CSF flow in the cerebral aqueduct and blood flow in the neck.RESULTS:The shear moduli of the brain tissue increased with the percentage of blood draining through the internal jugular veins during venous compression. Peak velocity of caudally directed CSF in the aqueduct increased significantly with jugular compression (P < .001). The mean jugular venous flow rate, amplitude, and vessel area were significantly reduced with jugular compression, while cranial arterial flow parameters were unaffected.CONCLUSIONS:Jugular compression influences cerebral CSF hydrodynamics in healthy subjects and can increase brain tissue stiffness, but the magnitude of the stiffening depends on the percentage of cranial blood draining through the internal jugular veins during compression—that is, subjects who maintain venous drainage through the internal jugular veins during jugular compression have stiffer brains than those who divert venous blood through alternative pathways. These methods may be useful for studying this phenomenon in patients with the syndrome of inappropriately low-pressure acute hydrocephalus and other conditions.

Changes in venous drainage from the cranium, such as reduction in internal jugular vein flow when moving from a supine to upright posture, can alter cerebral hemodynamics and CSF dynamics.¹ However, postural changes are difficult to study by using brain MR imaging. There is recent clinical interest in understanding how cranial venous outflow affects the brain, in part due to the controversial chronic cerebrospinal venous insufficiency hypothesis.²Reduction in venous outflow through the internal jugular veins, through the use of an elastic bandage (neck wrap), has also been used as a treatment for the syndrome of inappropriately low-pressure acute hydrocephalus (SILPAH),³ also known as negative or low-pressure hydrocephalus, rapidly reversing ventriculomegaly and restoring neurologic function.^4–8 SILPAH is a rare and enigmatic condition in which patients exhibit ventriculomegaly and very low intracranial pressure⁹ associated with obstruction to the CSF pathways between the ventricles and the subarachnoid space. Despite low intracranial pressure, symptoms mirror those of high intracranial pressure.^4–7,9–12 The pathophysiology for SILPAH remains unclear. However, changes in brain stiffness as a result of the loss of extracellular fluid^{4,8,9,11–13} combined with CSF leaks⁶ have been suggested. Jugular compression has also been observed to increase the amplitude of CSF waveforms in the cervical subarachnoid space in subjects whose venous drainage took place primarily through the internal jugular veins and to decrease the amplitudes in subjects with primarily extrajugular drainage.¹⁴ These changes may be related to alterations in intracranial pressure arising from increased dural venous pressure⁴ and stiffening of brain tissue.^4,6,8 However, the relationships between cranial venous drainage routes, cerebral CSF flow, and brain tissue properties in the context of jugular compression have not been investigated, to our knowledge.Viscoelastic tissue response to loading consists of a recoverable elastic component and a nonrecoverable viscous component. The response to shear loading comprises the shear storage (G′) and loss (G″) moduli, representing elastic and viscous components, respectively. Increases in the shear moduli reflect higher stiffness.MR elastography (MRE)¹⁵ is a noninvasive imaging technique that measures tissue stiffness by imaging the propagation of mechanical vibration with motion-sensitive gradients. Viscoelastic properties are quantified by analyzing the wave-propagation characteristics. MRE has been used to quantify the viscoelastic properties of healthy in vivo brain tissue^16–18 and brain disorders such as normal pressure hydrocephalus.^19,20 The shear moduli obtained depend on the vibration frequency, with lower values obtained at low frequencies.In this study, we aimed to use MRE to determine the effect of restricting cranial venous outflow by using bilateral jugular compression on brain stiffness and CSF flow in healthy volunteers. We hypothesized that brain viscoelasticity and CSF velocity would increase with jugular compression.     

Comparison of High-Resolution MR Imaging and Digital Subtraction Angiography for the Characterization and Diagnosis of Intracranial Artery Disease

BACKGROUND AND PURPOSE:High-resolution MR imaging has recently been introduced as a promising diagnostic modality in intracranial artery disease. Our aim was to compare high-resolution MR imaging with digital subtraction angiography for the characterization and diagnosis of various intracranial artery diseases.MATERIALS AND METHODS:Thirty-seven patients who had undergone both high-resolution MR imaging and DSA for intracranial artery disease were enrolled in our study (August 2011 to April 2014). The time interval between the high-resolution MR imaging and DSA was within 1 month. The degree of stenosis and the minimal luminal diameter were independently measured by 2 observers in both DSA and high-resolution MR imaging, and the results were compared. Two observers independently diagnosed intracranial artery diseases on DSA and high-resolution MR imaging. The time interval between the diagnoses on DSA and high-resolution MR imaging was 2 weeks. Interobserver diagnostic agreement for each technique and intermodality diagnostic agreement for each observer were acquired.RESULTS:High-resolution MR imaging showed moderate-to-excellent agreement (interclass correlation coefficient = 0.892–0.949; κ = 0.548–0.614) and significant correlations (R = 0.766–892) with DSA on the degree of stenosis and minimal luminal diameter. The interobserver diagnostic agreement was good for DSA (κ = 0.643) and excellent for high-resolution MR imaging (κ = 0.818). The intermodality diagnostic agreement was good (κ = 0.704) for observer 1 and moderate (κ = 0.579) for observer 2, respectively.CONCLUSIONS:High-resolution MR imaging may be an imaging method comparable with DSA for the characterization and diagnosis of various intracranial artery diseases.

Intracranial artery disease (ICAD) is one of the major causes of ischemic stroke and neurologic symptoms.^1–3 ICAD generally presents with intracranial artery stenosis on luminal evaluation, even though it includes various ICADs, such as atherosclerosis, dissection, Moyamoya disease, and vasculitis. The degree of stenosis has been the most common and important characteristic for evaluating ICAD and determining the treatment options.^4,5Luminal angiography, such as digital subtraction angiography, CT angiography, and MR angiography, has been widely used and has functioned successfully for the evaluation of stenosis and the diagnosis of ICAD. Among these methods, DSA is thought to be the criterion standard tool compared with the other modalities because it depicts luminal geometric shapes and hemodynamic information with higher resolution.^6–8 However, DSA has several limitations. It only depicts the luminal morphology and not the vessel walls directly, and many diseases share nonspecific luminal findings. Because DSA is also an invasive procedure with the risk of neurologic complications and radiation exposure, it is not suitable for screening or serial examinations.^9–11 Accordingly, CTA and MRA have been commonly used as the minimally invasive method to diagnose and differentiate intracranial artery disease in the clinical field, though they have more drawbacks in the luminal evaluation to DSA.High-resolution MR imaging (HR-MR) has recently been introduced as a minimally invasive and promising advanced imaging technique for directly depicting the intracranial arterial wall.^12,13Although HR-MR evaluates and differentiates various ICADs with the direct depiction of arterial walls and multicontrast images^6,14–20 that may correlate with luminal angiography,^8,21,22 the usefulness and value of HR-MR compared with luminal angiography are still unclear. Only a few studies presented a comparison or correlation between DSA and HR-MR,^8,13,23 and these studies showed a good correlation regarding the degree of stenosis^8,23 and HR-MR features beyond DSA.¹³ However, the observations were based on single vascular pathology or a single cerebral artery (middle cerebral artery, basilar artery) or a small sample size (n = 9).In our study, we compared HR-MR with DSA in the characterization and diagnosis of various ICADs. We hypothesized that HR-MR may be an imaging method comparable with DSA for the characterization and diagnosis of ICAD.     

Utility of Proton MR Spectroscopy for Differentiating Typical and Atypical Primary Central Nervous System Lymphomas from Tumefactive Demyelinating Lesions

BACKGROUND AND PURPOSE:It may be challenging to differentiate primary CNS lymphomas, especially primary CNS lymphomas with atypical MR features, from tumefactive demyelinating lesions by the use of conventional MR. This study aimed to investigate the usefulness of ¹H-MR spectroscopy for making this discrimination.MATERIALS AND METHODS:Forty-four patients with primary CNS lymphomas and 21 with tumefactive demyelinating lesions were enrolled. Single-voxel (TE = 144 ms) ¹H-MR spectroscopy scans with the use of the point-resolved spectroscopy sequence were retrospectively analyzed. The Cho/Cr and Cho/NAA area ratios were calculated. The lipid and/or lactate peak was visually categorized into 5 grades on the basis of comparison with the height of the Cr peak. The ¹H-MR spectroscopy findings were compared in all of the primary CNS lymphomas and the tumefactive demyelinating lesions and in the subgroup of atypical primary CNS lymphomas and tumefactive demyelinating lesions. The thresholds and added value of ¹H-MR spectroscopy to conventional MR were calculated by use of receiver operating characteristic curves.RESULTS:Discrepancies between all of the primary CNS lymphomas and tumefactive demyelinating lesions were found in the Cho/Cr ratio (P = .000), Cho/NAA ratio (P = .000), and the lipid and/or lactate peak grade (P = .000). Lymphoma rather than tumefactive demyelinating lesions was suggested when the Cho/Cr ratio was >2.58, the Cho/NAA ratio was >1.73, and a high lipid and/or lactate peak grade (grade >3) was seen. Higher Cho/Cr ratios, Cho/NAA ratios, and lipid and/or lactate peak grades were found in atypical primary CNS lymphomas when compared with those of tumefactive demyelinating lesions. The area under the receiver operating characteristic curve of conventional MR was improved from 0.827 to 0.870 when Cho/NAA ratio was added in the uncertain cases.CONCLUSIONS:¹H-MR spectroscopy may be useful for differentiating primary CNS lymphomas from tumefactive demyelinating lesions. Cho/NAA ratio could provide added value to conventional MR imaging.

Primary central nervous system lymphomas (PCNSLs) are aggressive tumors that represent approximately 1–6% of primary intracranial neoplasms.¹ Their incidence has been increasing during the past 2 decades not only in immunocompromised patients but also in immunocompetent patients.^2,3 Typical MR imaging features of PCNSLs are characterized by their periventricular locations, well-defined margin, moderate or marked edema, and intense and homogeneous nodular enhancement and are usually easy to correctly diagnose.^4–6 However, some patients present with atypical MR imaging features, commonly those of heterogeneous enhancement, such as patchy enhancement, streaky enhancement without mass formation, or even no enhancement.^6–9Demyelinating diseases of the CNS are pathologic entities that are frequently encountered in clinical practice. When such lesions appear as solitary masses >2 cm in the longest diameter, they are defined as tumefactive demyelinating lesions (TDLs), and they can cause symptoms mimicking brain neoplasms and can be associated with variable enhancement on MR imaging.¹⁰ Differentiation between PCNSLs and TDLs by use of conventional MR can sometimes be challenging, especially when there are atypical MR imaging features in PCNSLs. Considering the rapid progress of PCNSLs, early differentiation is important because both the treatment effectiveness and the patient survival rate will substantially decrease if there is delayed radiation therapy and/or chemotherapy.⁷ Accurate differentiation is also important to avoid unnecessary biopsies of TDLs.¹H-MR spectroscopy can provide noninvasive biochemical information regarding in vivo tissue. Some authors have suggested that ¹H-MR spectroscopy is helpful for discriminating tumors and pseudotumors,^11,12 whereas others argue that it may not be so, because there is some overlap of the metabolites.^13,14 There are many published ¹H-MR spectroscopy studies of PCNSLs as well as TDLs^3,10,15,16; however, to our knowledge, there is still no ¹H-MR spectroscopy study that distinguishes PCNSLs from TDLs. Our current study attempts to investigate the potential clinical utility of ¹H-MR spectroscopy for differentiating PCNSLs from TDLs and further focuses on evaluating whether ¹H-MR spectroscopy is also helpful for discriminating PCNSLs with atypical MR imaging features from TDLs.     

Diffusion and Perfusion MRI Findings of the Signal-Intensity Abnormalities of Brain Associated with Developmental Venous Anomaly

BACKGROUND AND PURPOSE:Developmental venous anomalies are the most common intracranial vascular malformation. Increased signal-intensity on T2-FLAIR images in the areas drained by developmental venous anomalies are encountered occasionally on brain imaging studies. We evaluated diffusion and perfusion MR imaging findings of the abnormally high signal intensity associated with developmental venous anomalies to describe their pathophysiologic nature.MATERIALS AND METHODS:We retrospectively reviewed imaging findings of 34 subjects with signal-intensity abnormalities associated with developmental venous anomalies. All subjects underwent brain MR imaging with contrast and diffusion and perfusion MR imaging. Regions of interest were placed covering abnormally high signal intensity around developmental venous anomalies on fluid-attenuated inversion recovery imaging, and the same ROIs were drawn on the corresponding sections of the diffusion and perfusion MR imaging. We measured the apparent diffusion coefficient, relative cerebral blood volume, relative mean transit time, and time-to-peak of the signal-intensity abnormalities around developmental venous anomalies and compared them with the contralateral normal white matter. The Mann-Whitney U test was used for statistical analysis.RESULTS:The means of ADC, relative cerebral blood volume, relative mean transit time, and TTP of signal-intensity abnormalities around developmental venous anomalies were calculated as follows: 0.98 ± 0.13 10⁻³mm²/s, 195.67 ± 102.18 mL/100 g, 16.74 ± 7.38 seconds, and 11.65 ± 7.49 seconds, respectively. The values of normal WM were as follows: 0.74 ± 0.08 10⁻³mm²/s for ADC, 48.53 ± 22.85 mL/100 g for relative cerebral blood volume, 12.12 ± 4.27 seconds for relative mean transit time, and 8.35 ± 3.89 seconds for TTP. All values of ADC, relative cerebral blood volume, relative mean transit time, and TTP in the signal-intensity abnormalities around developmental venous anomalies were statistically higher than those of normal WM (All P < .001, respectively).CONCLUSIONS:The diffusion and perfusion MR imaging findings of the signal-intensity abnormalities associated with developmental venous anomaly suggest that the nature of the lesion is vasogenic edema with congestion and delayed perfusion.

Developmental venous anomalies (DVAs) are encountered frequently on brain imaging studies. DVAs are identified in up to 2% of the general population, and they are the most common intracranial vascular malformation (63% and 50% of all malformations in postmortem examinations and MR imaging series, respectively).^1,2 They are composed of dilated medullary veins that drain centripetally and radially into enlarged transcortical or subependymal collector veins.^3–5 DVAs serve as normal drainage routes of the brain tissue because the normal venous drainage pattern is underdeveloped in the area adjacent to the DVA. These venous channels have no malformed or neoplastic elements and are generally described as having normal intervening parenchyma.^6,7 However, increased signal intensity (SI) on T2 FLAIR images in the areas drained by DVAs have been reported in 7.8%–54.1% of MR imaging investigations.^8–10 Such abnormal SI related to DVAs has been explained as edema, ischemia, demyelination, gliosis, leukoaraiosis, or a combination of these conditions.^11,12 Several studies have been undertaken to understand the mechanism of SI change.^13–15 However, there has been no report of the diffusion and perfusion changes of abnormal SI in the area of DVAs by using diffusion- and perfusion-weighted MR imaging, to our knowledge. Therefore, the aim of this study was to characterize these SIs by using DWI and PWI. DWI would discriminate between vasogenic edema and gliosis, and PWI would demonstrate signs of outflow obstruction and venous congestion.     

Differentiation between Treatment-Induced Necrosis and Recurrent Tumors in Patients with Metastatic Brain Tumors: Comparison among 11C-Methionine-PET,FDG-PET,MR Permeability Imaging,and MRI-ADC—Preliminary Results

BACKGROUND AND PURPOSE:In patients with metastatic brain tumors after gamma knife radiosurgery, the superiority of PET using ¹¹C-methionine for differentiating radiation necrosis and recurrent tumors has been accepted. To evaluate the feasibility of MR permeability imaging, it was compared with PET using ¹¹C-methionine, FDG-PET, and DWI for differentiating radiation necrosis from recurrent tumors.MATERIALS AND METHODS:The study analyzed 18 lesions from 15 patients with metastatic brain tumors who underwent gamma knife radiosurgery. Ten lesions were identified as recurrent tumors by an operation. In MR permeability imaging, the transfer constant between intra- and extravascular extracellular spaces (/minute), extravascular extracellular space, the transfer constant from the extravascular extracellular space to plasma (/minute), the initial area under the signal intensity–time curve, contrast-enhancement ratio, bolus arrival time (seconds), maximum slope of increase (millimole/second), and fractional plasma volume were calculated. ADC was also acquired. On both PET using ¹¹C-methionine and FDG-PET, the ratio of the maximum standard uptake value of the lesion divided by the maximum standard uptake value of the symmetric site in the contralateral cerebral hemisphere was measured (¹¹C-methionine ratio and FDG ratio, respectively). The receiver operating characteristic curve was used for analysis.RESULTS:The area under the receiver operating characteristic curve for differentiating radiation necrosis from recurrent tumors was the best for the ¹¹C-methionine ratio (0.90) followed by the contrast-enhancement ratio (0.81), maximum slope of increase (millimole/second) (0.80), the initial area under the signal intensity–time curve (0.78), fractional plasma volume (0.76), bolus arrival time (seconds) (0.76), the transfer constant between intra- and extravascular extracellular spaces (/minute) (0.74), extravascular extracellular space (0.68), minimum ADC (0.60), the transfer constant from the extravascular extracellular space to plasma (/minute) (0.55), and the FDG-ratio (0.53). A significant difference in the ¹¹C-methionine ratio (P < .01), contrast-enhancement ratio (P < .01), maximum slope of increase (millimole/second) (P < .05), and the initial area under the signal intensity–time curve (P < .05) was evident between radiation necrosis and recurrent tumor.CONCLUSIONS:The present study suggests that PET using ¹¹C-methionine may be superior to MR permeability imaging, ADC, and FDG-PET for differentiating radiation necrosis from recurrent tumors after gamma knife radiosurgery for metastatic brain tumors.

Stereotactic radiosurgery such as gamma knife radiosurgery (GK) and CyberKnife (Accuray, Sunnyvale, California) is an effective method for treating intracranial neoplasms.^1,2 For metastatic tumors of the brain, stereotactic radiosurgery has generally been the main tool used in therapeutic regimens.^3,4 Although stereotactic radiosurgery is an effective treatment method, it has a risk of radiation necrosis. Radiation necrosis after stereotactic radiosurgery for metastatic tumors of the brain is more common than previously reported.^5,6 It generally occurs 3–12 months after therapy⁷ and often resembles recurrent tumors on conventional imaging techniques, such as MR imaging,^8–11 CT,¹² and SPECT.¹³ Differentiating radiation necrosis and recurrent tumor is extremely important because of the different treatment implications. Histologic examination from a biopsy or resection may aid in differentiating these 2 events. However, a noninvasive method is needed for diagnosing whether a contrast-enhanced lesion with surrounding edema on conventional MR imaging is radiation necrosis or a recurrent tumor.Advanced MR imaging techniques including MR spectroscopy,¹⁴ DWI,¹⁵ and DTI¹⁶ have been used for differentiation of radiation necrosis and recurrent tumors. The CTP technique has also been reported as promising in this field.¹⁷ CTP has the advantage of using widely available CT scanners, though x-ray exposure and administration of ionizing contrast material limit the clinical use. In radionuclide studies, SPECT with ²⁰¹TI-chloride,¹⁸ technetium Tc99m-sestamibi,^{19 123}I-alfa-methyl-L-tyrosine,²⁰O-(2-[¹⁸F]-fluoroethyl)-L-tyrosine (FET-PET),^21,22 6-[¹⁸F]-fluoro-L-dopa (FDOPA),²³ and FDG-PET^24–26 have been reported to differentiate between radiation necrosis and recurrent tumors. Compared with those studies, the superiority of PET with ¹¹C-methionine (MET) for differentiating radiation necrosis and recurrent tumors has been accepted because of the high sensitivity and specificity.^27–31 However, MET-PET is not widely available. Dynamic contrast-enhanced MR imaging with a contrast agent has been used to characterize brain tumors^32,33 and stroke.³⁴MR permeability imaging with dynamic contrast-enhanced–MR imaging based on the Tofts model³⁵ has recently been developed and used for evaluating cerebrovascular diseases,³⁶ brain tumors,^37–39 nasopharyngeal carcinomas,^40,41 rectal carcinomas,⁴² and prostate carcinomas.⁴³ The endothelial permeability of vessels in brain tumors can be quantitatively acquired with MR permeability imaging. The vascular microenvironment in tumors can be measured by parameters such as influx transfer constant, reverse transfer constant, and the extravascular extracellular space.⁴⁴ These parameters may reflect tissue characteristics including vascular density, a damaged blood-brain barrier, vascularity, and neoangiogenesis.⁴⁴ If the feasibility of MR permeability imaging for differentiating radiation necrosis and recurrent tumors could be demonstrated, this technique may contribute to the management of patients after stereotactic radiosurgery and conventional radiation therapy because MR permeability imaging is widely available. To evaluate the feasibility of MR permeability imaging in the present study, we compared it with MET-PET, FDG-PET, and DWI for differentiating radiation necrosis from recurrent tumor after GK in patients with metastatic brain tumors.     

Pretreatment Advanced Imaging in Patients with Stroke Treated with IV Thrombolysis: Evaluation of a Multihospital Data Base

BACKGROUND AND PURPOSE:CT angiography, CT perfusion, and MR imaging have all been advocated as potentially useful in treatment planning for patients with acute ischemic stroke. We evaluated a large multihospital data base to determine how the use of advanced imaging is evolving in patients treated with intravenous thrombolysis.MATERIALS AND METHODS:Patients with acute ischemic stroke receiving IV thrombolytic therapy from 2008 to 2011 were identified by using the Premier Perspective data base. Mortality and discharge to long-term care rates were compared following multivariate logistic regression between patients who received head CT only versus those who received CTA without CT perfusion, CT perfusion, or MR imaging.RESULTS:Of 12,429 included patients, 7305 (59%) were in the CT group, 2359 (19%) were in the CTA group, 848 (7%) were in the CTP group, and 1917 (15%) were in the MR group. From 2008 to 2011, the percentage of patients receiving head CT only decreased from 64% to 55%, while the percentage who received cerebral CT perfusion increased from 3% to 8%. The use of CT angiography and MR imaging marginally increased (1%–2%). Outcomes were similar between CT only and advanced imaging patients, except discharge to long-term care was slightly more frequent in the CTP group (OR = 1.17 [95% CI, 0.96–1.43]; P = .0412) and MR group (OR = 1.14 [95% CI, 1.01–1.28]; P = .0177) and mortality was lower in the MR group (OR = 0.64 [95% CI, 0.52–0.79]; P < .0001).CONCLUSIONS:Use of advanced imaging is increasing in patients treated with IV thrombolysis. While there were differences in outcomes among imaging groups, the clinical effect of advanced imaging remains unclear.

The potential benefit of intravenous thrombolytic therapy for acute ischemic stroke decreases rapidly with time. Because of wide variability in collateral circulation, time elapsed since onset is a crude indicator of the potential benefit of treatment in each patient. Advanced imaging might provide a means to refine selection of patients who could potentially benefit from revascularization therapy. The advanced imaging techniques that might add clinically useful information in the setting of acute ischemic stroke include CT angiography, CT perfusion, and MR imaging. CT angiography can be used to identify patients with large-artery occlusions potentially amenable to intra-arterial therapy,^1–3 and CT angiography source images have been proposed as a means of evaluating collateral circulation.^4–6 CT perfusion may potentially allow discrimination between salvageable brain (“penumbra”) and brain already doomed to infarction (“ischemic core”)^2,7–10 and thus may be useful in helping to refine selection of patients for IV thrombolysis^11,12 or intra-arterial thrombectomy.^13–15 MR perfusion and diffusion imaging have also been reported to be useful in screening patients for intravenous therapy.^16–22While advanced imaging techniques hold promise for the evaluation of patients with acute ischemic stroke, there is variation in techniques and definitions of parameters that limit wide application and acceptance of these techniques.^4,23–25 There is currently no consensus on a standard imaging approach for acute ischemic stroke. We studied a large data base of hospitals in the United States to assess the recent use of advanced imaging in patients with acute ischemic stroke treated with intravenous thrombolysis, including an evaluation of the use of advanced imaging, with respect to patient outcome.     

Diagnostic Value of Prenatal MR Imaging in the Detection of Brain Malformations in Fetuses before the 26th Week of Gestational Age

BACKGROUND AND PURPOSE:In several countries, laws and regulations allow abortion for medical reasons within 24–25 weeks of gestational age. We investigated the diagnostic value of prenatal MR imaging for brain malformations within 25 weeks of gestational age.MATERIALS AND METHODS:We retrospectively included fetuses within 25 weeks of gestational age who had undergone both prenatal and postnatal MR imaging of the brain between 2002 and 2014. Two senior pediatric neuroradiologists evaluated prenatal MR imaging examinations blinded to postnatal MR imaging findings. With postnatal MR imaging used as the reference standard, we calculated the sensitivity, specificity, positive predictive value, and negative predictive value of the prenatal MR imaging in detecting brain malformations.RESULTS:One-hundred nine fetuses (median gestational age at prenatal MR imaging: 22 weeks; range, 21–25 weeks) were included in this study. According to the reference standard, 111 malformations were detected. Prenatal MR imaging failed to detect correctly 11 of the 111 malformations: 3 midline malformations, 5 disorders of cortical development, 2 posterior fossa anomalies, and 1 vascular malformation. Prenatal MR imaging misdiagnosed 3 findings as pathologic in the posterior fossa.CONCLUSIONS:The diagnostic value of prenatal MR imaging between 21 and 25 weeks'' gestational age is very high, with limitations of sensitivity regarding the detection of disorders of cortical development.

Prenatal MR imaging of the brain is a technique increasingly used in clinical practice; it is generally performed as a second-look investigation in case of abnormal or suspicious findings at prenatal ultrasonography (US).¹Prenatal MR imaging is often advocated as an important tool in parental counseling and decision-making regarding the fate of the pregnancy.² In several countries, crucial decisions on pregnancy must be made before the 24th to 25th week of gestation because local laws and regulations allow abortion for medical reasons within this deadline. In these cases, a correct diagnosis should be reached early during pregnancy because performing additional MR imaging follow-up is not compatible with legal time constraints. Moreover, an early correct diagnosis may have an important impact on the psychological well-being of the mother and may help the clinician in planning other diagnostic or therapeutic procedures.To determine prenatal MR imaging accuracy, several studies have already compared its results with ones from postmortem examinations,^3–5 postnatal MR imaging,^6–11 or both postmortem examination and postnatal MR imaging.^12,13 However, these studies were performed in small cohorts of fetuses, and they were focused on a single specific class of anomalies or accounted for few fetuses younger than 24–25 weeks'' gestational age (GA), thus providing little information about the diagnostic accuracy of prenatal MR imaging performed at an early GA.The purpose of our study was to assess the diagnostic value of prenatal MR imaging in the diagnosis of brain malformations, in a large cohort of fetuses (109 cases) within 25 weeks of GA, by using postnatal MR imaging as the reference standard.     

Identification of the Inflow Zone of Unruptured Cerebral Aneurysms: Comparison of 4D Flow MRI and 3D TOF MRA Data

BACKGROUND AND PURPOSE:The hemodynamics of the inflow zone of cerebral aneurysms may be a key factor in coil compaction and recanalization after endovascular coil embolization. We performed 4D flow MR imaging in conjunction with 3D TOF MRA and compared their ability to identify the inflow zone of unruptured cerebral aneurysms.MATERIALS AND METHODS:This series comprised 50 unruptured saccular cerebral aneurysms in 44 patients. Transluminal color-coded 3D MRA images were created by selecting the signal-intensity ranges on 3D TOF MRA images that corresponded with both the luminal margin and the putative inflow.RESULTS:4D flow MR imaging demonstrated the inflow zone and yielded inflow velocity profiles for all 50 aneurysms. In 18 of 24 lateral-projection aneurysms (75%), the inflow zone was located distally on the aneurysmal neck. The maximum inflow velocity ranged from 285 to 922 mm/s. On 4D flow MR imaging and transluminal color-coded 3D MRA studies, the inflow zone of 32 aneurysms (64%) was at a similar location. In 91% of aneurysms whose neck section plane angle was <30° with respect to the imaging section direction on 3D TOF MRA, depiction of the inflow zone was similar on transluminal color-coded 3D MRA and 4D flow MR images.CONCLUSIONS:4D flow MR imaging can demonstrate the inflow zone and provide inflow velocity profiles. In aneurysms whose angle of the neck-section plane is obtuse vis-a-vis the imaging section on 3D TOF MRA scans, transluminal color-coded 3D MRA may depict the inflow zone reliably.

Although endovascular coil embolization has become a major tactic to address cerebral aneurysms, recanalization or recurrence, which may result in rebleeding, are important problems. Recanalization was reported in 6.1%–39.8% of patients who had undergone endovascular treatment,^1–6 and a meta-analysis found that 20.8% of treated aneurysms recurred.³ The rate of rerupture after endovascular treatment for ruptured aneurysms has ranged from 0.11% to 5.3%,^1,4,6 and the rupture rate in the first year after coil embolization was reported as 2.5%⁷ and 2.2%.⁸ Because hemodynamics acting on the aneurysmal inflow zone may play a key role in the development of coil compaction or recanalization after endovascular coil embolization, the aneurysmal inflow zone must be packed densely to preserve the durability of aneurysm obliteration and to prevent rerupture.^9–15The inflow through the aneurysmal neck into the dome can be seen on 3D TOF MRA images.^13,16,17 Satoh et al,^16,17 who used conventional 3D TOF MRA techniques to select threshold ranges based on the signal intensity of the volume-rendering data, determined the spatial signal-intensity distribution in aneurysms. They developed transluminal color-coded 3D MRA (TC 3D MRA) to improve visualization of the aneurysmal inflow. More recently, 4D flow MR imaging based on time-resolved 3D cine phase-contrast MR imaging techniques was used to evaluate the hemodynamics of cerebral aneurysms.^18–27 However, 4D flow MR imaging requires additional time for data acquisition, and TC 3D MRA may be a convenient alternative to 4D flow MR imaging for identifying the aneurysmal inflow zone.Here, we compared the ability of 4D flow MR imaging and TC 3D MRA to identify the inflow zone of cerebral aneurysms.     

Validation of an MRI Brain Injury and Growth Scoring System in Very Preterm Infants Scanned at 29- to 35-Week Postmenstrual Age

BACKGROUND AND PURPOSE:The diagnostic and prognostic potential of brain MR imaging before term-equivalent age is limited until valid MR imaging scoring systems are available. This study aimed to validate an MR imaging scoring system of brain injury and impaired growth for use at 29 to 35 weeks postmenstrual age in infants born at <31 weeks gestational age.MATERIALS AND METHODS:Eighty-three infants in a prospective cohort study underwent early 3T MR imaging between 29 and 35 weeks'' postmenstrual age (mean, 32⁺² ± 1⁺³ weeks; 49 males, born at median gestation of 28⁺⁴ weeks; range, 23⁺⁶–30⁺⁶ weeks; mean birthweight, 1068 ± 312 g). Seventy-seven infants had a second MR scan at term-equivalent age (mean, 40⁺⁶ ± 1⁺³ weeks). Structural images were scored using a modified scoring system which generated WM, cortical gray matter, deep gray matter, cerebellar, and global scores. Outcome at 12-months corrected age (mean, 12 months 4 days ± 1⁺² weeks) consisted of the Bayley Scales of Infant and Toddler Development, 3rd ed. (Bayley III), and the Neuro-Sensory Motor Developmental Assessment.RESULTS:Early MR imaging global, WM, and deep gray matter scores were negatively associated with Bayley III motor (regression coefficient for global score β = −1.31; 95% CI, −2.39 to −0.23; P = .02), cognitive (β = −1.52; 95% CI, −2.39 to −0.65; P < .01) and the Neuro-Sensory Motor Developmental Assessment outcomes (β = −1.73; 95% CI, −3.19 to −0.28; P = .02). Early MR imaging cerebellar scores were negatively associated with the Neuro-Sensory Motor Developmental Assessment (β = −5.99; 95% CI, −11.82 to −0.16; P = .04). Results were reconfirmed at term-equivalent-age MR imaging.CONCLUSIONS:This clinically accessible MR imaging scoring system is valid for use at 29 to 35 weeks postmenstrual age in infants born very preterm. It enables identification of infants at risk of adverse outcomes before the current standard of term-equivalent age.

Preterm infants are at risk of brain injury and impaired brain growth and consequently poorer outcomes in infancy and childhood.^1–6 Scoring of structural MR imaging to classify brain injury and growth has been validated for use at term-equivalent age (TEA) in infants born preterm.^1,7 Initial systems were qualitative, focusing on classification of the severity of WM and cortical gray matter (CGM) injuries.^7–9 The degree of WM abnormality demonstrated significant associations with concurrent motor, neurologic, and neurobehavioral performance^10–13 and increasing WM abnormality was associated with poorer motor and cognitive outcomes.^{1,2,5,7,14–16}Scoring systems of MR imaging at TEA were further developed to include quantitative biometrics to measure the impact of secondary brain maturation and growth following preterm brain injury.¹⁷ These brain metrics correlated with brain volumes and differentiated preterm and term-born infants at TEA MR imaging.¹⁷ At TEA, transcerebellar diameter was associated with fidgety general movements at 3-month corrected age (CA),¹⁸ poorer cognitive outcomes at 12-month CA,¹⁹ and poorer motor and cognitive outcomes at 2-year CA.²⁰ Reduced deep gray matter area at TEA was associated with poorer motor and cognitive outcomes,¹⁹ and an increased interhemispheric distance independently predicted poorer cognitive development at 2-year CA.³ Reduced biparietal width at TEA predicted both motor and cognitive outcomes at 2-year CA in infants born very preterm.^3,21Term-equivalent age MR imaging scoring systems have been further developed to include evaluation of deep gray matter (DGM) structures and the cerebellum.²² At TEA, global brain abnormality scores were significantly associated with motor outcomes at 2-years CA²³; and cognitive outcomes, at 7 years.^24,25 Deep gray matter scores were significantly associated with poorer attention and processing speeds, memory, and learning.^24,25With safe earlier MR imaging now possible with MR compatible incubators, valid scoring systems for use earlier than TEA are required. The aim of this study was to validate an MR imaging scoring system previously developed for very preterm infants at TEA in a cohort of infants born <31-weeks gestational age with MR imaging between 29 and 35 weeks'' postmenstrual age (PMA).²² The study aimed to establish predictive validity for motor and cognitive outcomes at 12-months CA. Secondary aims were to examine inter- and intrarater reproducibility and to examine relationships between global brain abnormality categories and known perinatal risk factors. It was hypothesized that the scoring system would be valid and reliable for use at this earlier time point but with more infants classified with brain abnormalities, due to immaturity rather than injury.     

Hydrocephalus Decreases Arterial Spin-Labeled Cerebral Perfusion

BACKGROUND AND PURPOSE:Reduced cerebral perfusion has been observed with elevated intracranial pressure. We hypothesized that arterial spin-labeled CBF can be used as a marker for symptomatic hydrocephalus.MATERIALS AND METHODS:We compared baseline arterial spin-labeled CBF in 19 children (median age, 6.5 years; range, 1–17 years) with new posterior fossa brain tumors and clinical signs of intracranial hypertension with arterial spin-labeled CBF in 16 age-matched controls and 4 patients with posterior fossa tumors without ventriculomegaly or signs of intracranial hypertension. Measurements were recorded in the cerebrum at the vertex, deep gray nuclei, and periventricular white matter and were assessed for a relationship to ventricular size. In 16 symptomatic patients, we compared cerebral perfusion before and after alleviation of hydrocephalus.RESULTS:Patients with uncompensated hydrocephalus had lower arterial spin-labeled CBF than healthy controls for all brain regions interrogated (P < .001). No perfusion difference was seen between asymptomatic patients with posterior fossa tumors and healthy controls (P = 1.000). The median arterial spin-labeled CBF increased after alleviation of obstructive hydrocephalus (P < .002). The distance between the frontal horns inversely correlated with arterial spin-labeled CBF of the cerebrum (P = .036) but not the putamen (P = .156), thalamus (P = .111), or periventricular white matter (P = .121).CONCLUSIONS:Arterial spin-labeled–CBF was reduced in children with uncompensated hydrocephalus and restored after its alleviation. Arterial spin-labeled–CBF perfusion MR imaging may serve a future role in the neurosurgical evaluation of hydrocephalus, as a potential noninvasive method to follow changes of intracranial pressure with time.

Hydrocephalus is a common neurosurgical condition in children and adults, accounting for approximately 69,000 annual hospital admissions and 39,000 shunt procedures in the United States.^1,2 While concepts of hydrocephalus remain complex, including pathophysiology, diagnostic and therapeutic approaches,^3–5 and outcome,^6,7 it is generally accepted that hydrocephalus reflects pathologic dynamics among brain, spinal cord, blood, and CSF within a confined environment.^8–10 In clinical practice, imaging is often used to work-up hydrocephalus in search of obstructing lesions or the presence of ventriculomegaly. However, ventricular size, a frequently used imaging feature, does not always correlate with underlying CSF pressures or resorptive capacity for CSF^11–16 and, therefore, may not reliably identify compensated hydrocephalus without signs of raised intracranial pressure (ICP) and progressive hydrocephalus with raised ICP.Prior studies have shown reduced CBF with elevated ICP in various animal models of hydrocephalus.^17–20 Reduced CBF has also been reported in small case series of children with either congenital hydrocephalus or acute hydrocephalus from brain tumors by using ¹⁵O-PET²¹ or SPECT.²² Recently, 2D phase-contrast MRA has shown that carotid and basilar arterial flow rates are reduced in infants with hydrocephalus.²³ However, 2D phase-contrast MRA does not directly measure CBF at the tissue level and may be hampered by long scanning times and flow-sensitive technical challenges.^24,25In contrast, arterial spin-labeled (ASL) MR imaging perfusion directly measures tissue perfusion without requiring long scanning times, contrast, or radioisotope injection.²⁶ It is also uniquely advantageous in children with high labeling efficiency and SNR and can be repeated in the event of patient motion or after CSF diversion without the risk of radiation exposure.²⁷ While ASL perfusion has increasingly become clinically available, no studies have investigated its role for evaluating hydrocephalus. We hypothesized that ASL-CBF is reduced in uncompensated hydrocephalus and improved after its alleviation and, therefore, can be used as a marker for symptomatic hydrocephalus.     

MRI-Visible Perivascular Spaces in the Centrum Semiovale Are Associated with Brain Amyloid Deposition in Patients with Alzheimer Disease–Related Cognitive Impairment

BACKGROUND AND PURPOSE:The association of perivascular spaces in the centrum semiovale with amyloid accumulation among patients with Alzheimer disease–related cognitive impairment is unknown. We evaluated this association in patients with Alzheimer disease–related cognitive impairment and β-amyloid deposition, assessed with [¹⁸F] florbetaben PET/CT.MATERIALS AND METHODS:MR imaging and [¹⁸F] florbetaben PET/CT images of 144 patients with Alzheimer disease–related cognitive impairment were retrospectively evaluated. MR imaging–visible perivascular spaces were rated on a 4-point visual scale: a score of ≥3 or <3 indicated a high or low degree of MR imaging–visible perivascular spaces, respectively. Amyloid deposition was evaluated using the brain β-amyloid plaque load scoring system.RESULTS:Compared with patients negative for β-amyloid, those positive for it were older and more likely to have lower cognitive function, a diagnosis of Alzheimer disease, white matter hyperintensity, the Apolipoprotein E ε4 allele, and a high degree of MR imaging–visible perivascular spaces in the centrum semiovale. Multivariable analysis, adjusted for age and Apolipoprotein E status, revealed that a high degree of MR imaging–visible perivascular spaces in the centrum semiovale was independently associated with β-amyloid positivity (odds ratio, 2.307; 95% CI, 1.036–5.136; P = .041).CONCLUSIONS:A high degree of MR imaging–visible perivascular spaces in the centrum semiovale independently predicted β-amyloid positivity in patients with Alzheimer disease–related cognitive impairment. Thus, MR imaging–visible perivascular spaces in the centrum semiovale are associated with amyloid pathology of the brain and could be an indirect imaging marker of amyloid burden in patients with Alzheimer disease–related cognitive impairment.

Accumulating evidence suggests that MR imaging–visible perivascular spaces (PVS) are not innocent lesions but may be a neuroimaging marker of cerebral small-vessel disease.^1-3 The perivascular space is a potential space filled with interstitial fluid surrounding penetrating vessels. It is involved in the drainage of interstitial fluid and solutes from the brain.⁴ Therefore, several clinical conditions that reduce the clearance of solutes from the brain interstitial fluid such as aging, hypertension, and inflammation can result in MR imaging–visible PVS.⁵ MR imaging–visible PVS are also associated with various diseases, such as traumatic brain injury, Parkinson disease, and dementia.^6-9 The location of MR imaging–visible PVS is an important factor to consider when predicting disease status because MR imaging–visible PVS in the basal ganglia may be associated with markers of arteriolosclerosis, whereas MR imaging–visible PVS in the centrum semiovale (PVS-CS) are linked to diseases involving amyloid pathology, such as Alzheimer disease (AD) and cerebral amyloid angiopathy.^10,11Many different studies on cerebral amyloid angiopathy have demonstrated a strong relationship between MR imaging–visible PVS-CS and cerebral amyloid angiopathy.^12-15 Some studies have suggested that the dilation of PVS and failure in the drainage of interstitial fluid may result from deposition of β-amyloid in the cortical and leptomeningeal arteries.¹⁶ Furthermore, evidence indicates that MR imaging–visible PVS-CS are associated with in vivo β-amyloid deposition in the brain, based on amyloid PET scanning,^14,17 which enables the visualization of brain amyloid deposition and measures the distribution and density of β-amyloid plaques.¹⁸Failure in the perivascular clearance of β-amyloid may also be involved in the accumulation of β-amyloid in AD.¹⁹ In patients with AD, MR imaging–visible PVS-CS may reflect impaired perivascular clearance of β-amyloid, and several studies have indicated a link between MR imaging–visible PVS and AD.^7,20 However, unlike evidence for the association between MR imaging–visible PVS-CS and cerebral amyloid angiopathy, scant evidence exists regarding the association between β-amyloid deposition and MR imaging–visible PVS in the population with dementia.Several compounds labeled with radioisotopes have been developed to image amyloid deposition. In patients with cognitive impairment, PET scans using these tracers are widely used for diagnosis and follow-up.²¹ Among the radiopharmaceuticals, [¹⁸F] florbetaben ([¹⁸F] FBB) is widely used for PET imaging to evaluate AD and other causes of dementia. [¹⁸F] FBB has a proper half-life and also allows high-resolution image acquisition, diagnostic capability, and quantification.²² For these reasons, [¹⁸F] FBB is suitable for evaluating amyloid accumulation and its association with enlarged PVS in patients with dementia.We hypothesized that MR imaging–visible PVS-CS would be associated with brain amyloid deposition in cognitively impaired patients, as it is in patients with cerebral amyloid angiopathy. We also evaluated the association using [¹⁸F] FBB, a PET radiotracer that labels in vivo amyloid deposits, in patients with cognitive impairment.