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Objective-Individuals with 22q11.2 deletion syndrome are known to be at high risk of developing schizophrenia. Previous imaging studies have provided limited data on the relation of schizophrenia expression in 22q11.2 deletion syndrome to specific regional brain volumetric changes. The authors hypothesized that the main structural brain finding associated with schizophrenia expression in 22q11.2 deletion syndrome, as for schizophrenia in the general population, would be gray matter volumetric deficits, especially in the temporal lobes.Method-MR brain images from 29 patients with 22q11.2 deletion syndrome and schizophrenia and 34 comparison subjects with 22q11.2 deletion syndrome and no history of psychosis were analyzed using a voxel-based morphometry method that also yielded volumes for related regionof-interest analyses. The authors compared data from the two groups using an analysis of covariance model correcting for total intracranial volume, age, sex, IQ, and history of congenital cardiac defects. The false discovery rate threshold was set at 0.05 to account for multiple comparisons.Results-Voxel-based morphometry analyses identified significant gray matter reductions in the left superior temporal gyrus (Brodmann's area 22) in the schizophrenia group. There were no significant between-group differences in white matter or CSF volumes. Region-of-interest analyses showed significant bilateral gray matter volume reductions in the temporal lobes and superior temporal gyri in the schizophrenia group.Conclusions-The structural brain expression of schizophrenia associated with the highly penetrant 22q11.2 deletion involves lower gray matter volumes in temporal lobe regions. These structural MRI findings in a 22q11.2 deletion syndrome form of schizophrenia are consistent with those from studies involving schizophrenia samples from the general population. The results provide further support for 22q11.2 deletion syndrome as a genetic subtype and as a useful neurodevelopmental model of schizophrenia. CIHR Author Manuscript CIHR Author Manuscript CIHR Author ManuscriptOf the emerging copy number variations being identified as rare causes of schizophrenia, hemizygous 22q11.2 deletions are the genetic variants with the highest penetrance that convey the greatest elevation of risk for schizophrenia, estimated to be more than 20 times that of the general population (1, 2). Approximately one of every 100 patients with schizophrenia in the general population has a 22q11.2 deletion (3, 4). The associated 22q11.2 deletion syndrome, previously known as velocardiofacial or Di-George syndrome (Mendelian Inheritance of Man #188400, #192430), displays a variable phenotype with common features, including velopharyngeal insufficiency, congenital heart disease, and learning difficulties (5, 6). Mental retardation (IQ <70) is present in a minority of those with the syndrome (5,7,8). The 22q11.2 deletion syndrome has been proposed as a neurodevelopmental model of schizophrenia with enhanced genetic homogeneity that may help us u...

Voxel-based morphometry (VBM) and automated lobar region of interest (ROI) volumetry are comprehensive and fast methods to detect differences in overall brain anatomy on magnetic resonance images. However, VBM and automated lobar ROI volumetry have detected dissimilar gray matter differences within identical image sets in our own experience and in previous reports. To gain more insight into how diverging results arise and to attempt to establish whether one method is superior to the other, we investigated how differences in spatial scale and in the need to statistically correct for multiple spatial comparisons influence the relative sensitivity of either technique to group differences in gray matter volumes. We assessed the performance of both techniques on a small dataset containing simulated gray matter deficits and additionally on a dataset of 22q11-deletion syndrome patients with schizophrenia (22q11DS-SZ) vs. matched controls. VBM was more sensitive to simulated focal deficits compared to automated ROI volumetry, and could detect global cortical deficits equally well. Moreover, theoretical calculations of VBM and ROI detection sensitivities to focal deficits showed that at increasing ROI size, ROI volumetry suffers more from loss in sensitivity than VBM. Furthermore, VBM and automated ROI found corresponding GM deficits in 22q11DS-SZ patients, except in the parietal lobe. Here, automated lobar ROI volumetry found a significant deficit only after a smaller subregion of interest was employed. Thus, sensitivity to focal differences is impaired relatively more by averaging over larger volumes in automated ROI methods than by the correction for multiple comparisons in VBM. These findings indicate that VBM is to be preferred over automated lobarscale ROI volumetry for assessing gray matter volume differences between groups.

574In recent years, blunt cerebrovascular injury (BCVI) is gaining attention as an important sequela of nonpenetrating trauma to the neck and skull base. Blunt cerebrovascular injury affects approximately 1% of all blunt trauma admissions, and the reported incidence is as high as 2.7% in centres with aggressive screening protocols [1][2][3][4][5][6][7][8] . The pattern of BCVI consists of vascular transection, dissection, thrombosis, and formation of pseudoaneurysm or arteriovenous fistula (AVF) 9,10 . The majority of these injuries occur during motor vehicle accidents, with variable rates of carotid and vertebral artery involvement reported in the literature [11][12][13] . If untreated, BCVI can be fatal and result in devastating neurological sequelae, with mortality and morbidity rates reported up to 38% and 67% respectively 14 .One of the difficulties in initiating treatment for BCVI is related to the variable symptomatology. While approximately ABSTRACT: Background: Blunt cerebrovascular injury (BCVI) to the carotid and vertebral arteries is a potentially devastating injury in trauma patients. The optimal management for BCVI has not been standardized. At our institution, 64-slice multi-detector computed tomographic angiography (CTA) has been used as the initial screening exam for BCVI in patients who met predefined screening criteria. The purpose of this study is to review the incidence of CTA-diagnosed BCVI in at-risk patients and to evaluate the treatment and clinical outcome of patients with BCVI. Methods: This study included trauma patients with a positive diagnosis of BCVI on CTA during a 41-month study period. The medical records and relevant radiographic findings were retrospectively reviewed. Results: Twenty seven of 222 blunt trauma patients evaluated with CTA had a positive diagnosis of BCVI, with an occurrence rate of 12.2%. Traumatic brain injury (72.2%) and basal skull fractures (55.6%) were the most frequent associated injuries with carotid trauma while 100% of blunt vertebral injuries occurred in the setting of cervical fractures. Fourteen (51.8%) patients received medical therapy; Eleven (40.7%) patients received conservative treatment. Endovascular treatment was attempted in a single case of vertebral arteriovenous fistula. BCVI-related stroke was found in four patients (14.8%), one of whom developed an infarct while on medical treatment. Conclusions: BCVI is found in a significant portion of blunt trauma patients with identifiable risk factors, and screening CTA has high diagnostic yield in detecting these lesions. Medical therapy is the mainstay of treatment at our institution; however, BCVI-related stroke may occur despite treatment. RÉSUMÉ: Diagnostic et résultats du traitement des traumatismes cérébrovasclaires contondants. Contexte :Le traumatisme cérébrovasculaire contondant (TCVC) à la carotide et aux artères vertébrales est une lésion qui peut être dévastatrice chez les patients qui ont subi un traumatisme. Le traitement optimal du TCVC n'a pas été standardisé. Dans notre institutio...

Diffusion tensor magnetic resonance imaging (DTI) is the first and only non-invasive technique capable of delineating white matter (WM) pathways in vivo.1 Diffusion tensor magnetic resonance imaging can provide qualitative and quantitative information about the directionality (anisotropy) and magnitude (diffusivity) of water diffusion along a vector in 3-dimensional space.2-5 The success of diffusion imaging is related to the fact that during their random, diffusion-driven displacements, water molecules probe tissue structures at a microscopic scale well beyond conventional imaging resolution. 6 In WM fiber tracts, organized bundles of axonal membranes and myelin sheaths present substantial barriers to diffusion, especially in directions perpendicular to that of the fibers. These barriers render water ABSTRACT: Background: Diffusion tensor MRI fiber tractography (DTT) is the first non-invasive in vivo technique for delineating specific white matter (WM) tracts. In cerebral neoplasm, DTT can be used to illustrate the relationship of the tumor with respect to adjacent WM trajectories. Methods: Fiber tractography was used in this study to assess tumor-induced changes in WM trajectories in three cases of cerebral neoplasm: glioblastoma multiforme, meningioma, and anaplastic astrocytoma. Results: Three patterns of WM alteration were identified: 1) disruption, 2) displacement, and 3) infiltration. Tumor disruption of WM tracts was observed in glioblastoma multiforme, which terminated fibers crossing the corpus callosum. In meningioma, DTT illustrated bulk displacement of the corticospinal tract in the affected hemisphere as well as preservation of the deviated axons. In anaplastic astrocytoma, fiber tracking demonstrated disruption of WM tracts at the tumor origin as well as intact axons through areas of tumor infiltration. Conclusions: Fiber tracking results correlated with the clinical and histopathological features of the tumor. Larger case series will be required to determine if fiber tracking can add accuracy to existing imaging methods for grading tumors.RÉSUMÉ: Effet de masse de tumeurs sur la substance blanche cérébrale évalué par IRM en tenseur de diffusion. Contexte : La tractographie par IRM en tenseur de diffusion (TTD) pour étudier les fibres de la substance blanche (SB) est la première technique non effractive in vivo permettant de localiser des faisceaux spécifiques. Dans les tumeurs cérébrales, la TTD peut être utilisée pour illustrer la relation entre la tumeur et la trajectoire des faisceaux de la SB adjacents à la tumeur. Méthodes : La tractographie de faisceaux de fibres a été utilisée dans cette étude pour évaluer les changements induits par la tumeur dans la trajectoire de faisceaux de la SB chez trois cas de néoplasie cérébrale : un glioblastome multiforme, un méningiome et un astrocytome anaplasique. Résultats : Trois types de changements ont été identifiés dans la SB : 1) interruption; 2) déplacement et 3) infiltration. L' interruption de faisceaux de la SB à travers le corps calleux a été obs...

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