Localization of spinal dural arteriovenous fistulas from the spatial relationships of perimedullary vessels on standard MRI.

OBJECTIVE: The goal in this study was to explore the spatial relationship of perimedullary vessels visualized on MRI to localize the side and the site of spinal dural arteriovenous fistula (SDAVF). METHODS: A retrospective analysis of 30 consecutive patients diagnosed with SDAVF on MRI was undertaken. Two experienced reviewers blinded to all reports and angiographic images analyzed T2-weighted as well as postcontrast T1-weighted sequences. A focal prominent zone of perimedullary vessels with lateralization to one side in the thecal space was evaluated to locate the side and the site of the fistula. Spinal digital subtraction angiography served as the gold standard technique. RESULTS: Good interrater agreement (κ = 0.77) was shown for the diagnosis of SDAVF with perimedullary vessels on T2-weighted MRI. Flow voids on T2-weighted MRI demonstrated a sensitivity of 1.0 (95% CI 1.0-1.0) and an accuracy of 0.87 (95% CI 0.79-0.95) to identify the presence of fistula. The flow voids on T2-weighted MRI also demonstrated 0.88 (95% CI 0.71-1.03) sensitivity and 0.81 (95% CI 0.70-0.92) accuracy to identify the side of SDAVF. Furthermore, flow voids on T2-weighted MRI showed 0.87 (95% CI 0.71-1.03) sensitivity and 0.87 (95% CI 0.79-0.95) accuracy to identify the site of SDAVF within 3 vertebral levels above or below the actual site. Area under the receiver operating characteristic curve demonstrated significant results (0.87 [95% CI 0.73-1.0]; p < 0.001) for flow voids on T2-weighted MRI to identify the site of shunts within 3 vertebral levels in the cranial or caudal direction. CONCLUSIONS: Spatial distribution of perimedullary vessels observed on standard MRI show promise to locate the side and the site of fistula in patients with SDAVF.

Detection of cerebral cortical vein thrombosis with high-resolution susceptibility weighted imaging - A comparison with MR venography and standard MR sequences.

PURPOSE: Comparison of the performance of high-resolution susceptibility weighted imaging with standard MR sequences and MR venography to identify cortical vein clots. METHODS: A retrospective review of 51 consecutive cases of cerebral venous thrombosis and 27 controls was performed with independent analysis of all MR sequences. Reference standard was obtained with consensus in a separate session by reviewing all MR sequences together. RESULTS: Cortical vein clots were observed in 30 cases including 9 males and 21 females in the age range of 1 month to 70 years (Mean 34.9 ± 20.2 years). Sensitivity, specificity, negative predictive value, positive predictive value and accuracy of susceptibility weighted imaging for the identification of cortical vein clots were 0.93, 1.0, 1.0, 0.96 and 0.97 respectively. For all other sequences, sensitivity ranged from 0.06 to 0.39 and accuracy from 0.60 to 0.73. Combination of all sequences yielded a value of 1.0 for sensitivity, specificity, positive predictive value, negative predictive value and accuracy for the detection of cortical vein clots. Significant result for area under the receiver operating curve was observed only for SWI with a value of 0.91 (p - .000). CONCLUSION: Susceptibility weighted imaging demonstrates the best sensitivity and accuracy among standard MR sequences including MR venography for the detection of early stage cortical vein clots. However, it needs to be interpreted in combination with other MR sequences for the most accurate evaluation of cortical vein clots.

Temporal radiographic and histological study of necrosis development in a mouse glioblastoma model.

Tumor necrosis is a poor prognostic marker in glioblastoma (GBM) and a variety of other solid cancers. Accumulating evidence supports that necrosis could facilitate tumor progression and resistance to therapeutics. GBM necrosis is typically first detected by magnetic resonance imaging (MRI), after prominent necrosis has already formed. Therefore, radiological appearances of early necrosis formation and the temporal-spatial development of necrosis alongside tumor progression remain poorly understood. This knowledge gap leads to a lack of reliable radiographic diagnostic/prognostic markers in early GBM progression to detect necrosis. Recently, we reported an orthotopic xenograft GBM murine model driven by hyperactivation of the Hippo pathway transcriptional coactivator with PDZ-binding motif (TAZ) which recapitulates the extent of GBM necrosis seen among patients. In this study, we utilized this model to perform a temporal radiographic and histological study of necrosis development. We observed tumor tissue actively undergoing necrosis first appears more brightly enhancing in the early stages of progression in comparison to the rest of the tumor tissue. Later stages of tumor progression lead to loss of enhancement and unenhancing signals in the necrotic central portion of tumors on T1-weighted post-contrast MRI. This central unenhancing portion coincides with the radiographic and clinical definition of necrosis among GBM patients. Moreover, as necrosis evolves, two relatively more contrast-enhancing rims are observed in relationship to the solid enhancing tumor surrounding the central necrosis in the later stages. The outer more prominently enhancing rim at the tumor border probably represents the infiltrating tumor edge, and the inner enhancing rim at the peri-necrotic region may represent locally infiltrating immune cells. The associated inflammation at the peri-necrotic region was further confirmed by immunohistochemical study of the temporal development of tumor necrosis. Neutrophils appear to be the predominant immune cell population in this region as necrosis evolves. This study shows central, brightly enhancing areas associated with inflammation in the tumor microenvironment may represent an early indication of necrosis development in GBM.

A Quantitative Subarachnoid Hemorrhage Grading System, Including Supratentorial and Infratentorial Cisterns, With Multiplanar Computed Tomography Reformations.

Background Subarachnoid hemorrhage (SAH) grading scales typically evaluate a limited number of cisterns on the axial plane. The goal of our study is to apply a simple quantitative yet comprehensive SAH grading scale to all major intracranial cisterns, including the infratentorial cisterns, with multiplanar computed tomography (CT) reformations. Methodology We performed a retrospective review of 94 consecutive cases of spontaneous SAH presenting within 72 hours of onset. SAH was categorized into five grades based on the short-axis thickness of SAH in 20 intracranial cisterns measured on the axial, coronal, and sagittal planes. Statistical analysis was performed for inter-rater agreement with kappa statistics, for inter-plane agreement by Spearman correlation statistics, and for inter-rater and inter-plane agreement by Pearson correlation statistics. Results The extended kappa coefficient for the three reviewers across all 20 cisterns varied from 0.38 (0.27, 0.50) to 0.59 (0.52, 0.65) on the axial plane. The kappa coefficient for two reviewers varied from 0.46 (0.33, 0.59) to 0.70 (0.60, 0.80) on the coronal plane and from 0.35 (0.20, 0.49) to 0.87 (0.77, 0.96) on the sagittal plane. The average grade of cisterns per case demonstrated mostly excellent correlation between the imaging planes with Spearman correlation statistics (≥0.70). Pairwise concordance correlation coefficient of the total SAH score revealed agreement ranging from 0.81 to 0.90 in all three planes. Pearson correlation statistics of the average total SAH scores revealed excellent correlation among the three planes (≥0.91). Conclusion A simple quantitative SAH grading scale can be successfully applied to the supratentorial and infratentorial cisterns in three standard CT imaging planes.

High-resolution susceptibility-weighted imaging of clots in cerebral venous thrombosis.

PURPOSE: To distinguish cerebral venous clots from patent dural sinuses, cortical veins, and calvarium on high-resolution susceptibility-weighted imaging, since there is lack of a well-designed study in the literature. METHODS: A retrospective review of 51 consecutive cases and 27 controls was performed with susceptibility-weighted imaging independently by two investigators. MR venography along with MR sequences other than the susceptibility-weighted imaging served as the reference standard. RESULTS: There were 29 males and 49 females in the age range of 1 month to 70 years (mean 27 ± 19.8 years). Substantial (k 0.84 to 1.0) to good (k 0.60 to 0.75) inter-rater agreement was observed on the magnitude images for the demonstration of clots in all venous segments, excluding left sigmoid sinus, jugular bulb, and internal jugular vein (k 0.43 to 0.56). Comparatively magnitude images demonstrated better sensitivity (0.83 (0.54-1.13) to 1.0), specificity (0.92 (0.85-0.99) to 1.0), and negative predictive value (0.98 (0.94-1.02) to 1.0) for the detection of clots across all venous segments. Magnitude images showed positive predictive value ranging from 0.83 (0.66-1.0) to 1.0 for clots anywhere from the anterior aspect of superior sagittal sinus to bilateral transverse sinuses. For the detection of clots from bilateral sigmoid sinuses to internal jugular veins, magnitude images showed relatively better positive predictive value ranging from 0.57 (0.20-0.94) to 0.75 (0.45-1.06) in comparison to the processed magnitude and minimum intensity pixel images. CONCLUSION: Susceptibility-weighted imaging can successfully distinguish majority of clots from patent dural sinuses, cortical veins, and calvarium with excellent inter-rater agreements.

Role of Neurovascular Compression of Oculomotor Nerve in Ophthalmoplegic Migraine.

Ophthalmoplegic migraine is considered to occur more commonly in children than in adults. It commonly affects the oculomotor nerve among the cranial nerves. Demyelination of the nerve is proposed as the main mechanism for the etiology of ophthalmoplegic migraine, though it is not fully understood. Neurovascular compression as a cause of ophthalmoplegic migraine has not been well demonstrated in children. In this report, we present a case of a 13-year-old male with recurrent episodes of left ophthalmoplegic migraine. Oculomotor nerve enhancement with swelling was evident on MRI at the exit zone. Magnetic resonance angiography (MRA) revealed a sharp loop of the left posterior cerebral artery compressing the nerve. The case highlighted the unusual etiology of neurovascular compression resulting in ophthalmoplegic migraine in a pediatric patient. A supplemental case of ophthalmoplegic migraine in a seven-year-old male is also shown to highlight the role of neurovascular compression and the importance of using MR angiography to evaluate cases presenting clinically with ophthalmoplegic migraine.

Magnetic Resonance Angiography After Flow Diversion: The Use of Complementary Magnetic Resonance Angiography Techniques to Monitor Aneurysm Occlusion and Device and Arterial Branch Patency After Flow Diverter Placement.

BACKGROUND: Few studies have evaluated flow diversion with magnetic resonance angiography (MRA). Studies have shown better success of MRA in assessing the aneurysm response, but limited success in assessing stent patency. The patency of arterial branches on MRA remains to be explored. METHODS: Retrospective evaluation of 31 consecutive cases of carotid aneurysms treated with flow diversion was performed with noncontrast time-of-flight (TOF), contrast-enhanced TOF, and cine MRA (time-resolved angiography with interleaved stochastic trajectories) independently by 2 investigators for aneurysm occlusion, stent patency, and arterial branch patency. Digital subtraction angiography served as the gold standard technique. RESULTS: Patients were 6 men and 25 women with a mean ± SD age of 57.8 ± 12.27 years (range, 32-79 years). Stent patency, aneurysm occlusion, and branch patency mostly revealed substantial to perfect interobserver agreement (κ >0.60). Sensitivity, specificity, positive predictive value, and negative predictive value for stent patency on raw data images of TOF were 0.50, 0.86, 0.20, and 0.96 and on contrast-enhanced TOF were 1.0, 0.93, 0.50, and 1.0. Ranges for aneurysm response on the 3 MRA scans were 0.78-0.89 for sensitivity, 0.54-0.92 for specificity, 0.73-0.93 for positive predictive value, and 0.78-0.86 for negative predictive value. Ranges for arterial branch patency among the 3 MRA scans were 0.87-0.96 for sensitivity, 0.50-1.0 for specificity, 0.90-1.0 for positive predictive value, and 0.33-0.80 for negative predictive value. CONCLUSIONS: Aneurysm occlusion, stent patency, and arterial branch patency in flow diversion can be successfully evaluated with the combination of 3 MRA techniques.

Multiplanar CT evaluation of aneurysm rupture signs in subarachnoid hemorrhage.

PURPOSE: In subarachnoid hemorrhage, noncontrast CT features are used to guide the localization of ruptured aneurysms on CT angiography and DSA. Multiplanar CT may improve the localization of aneurysm rupture sites over axial plane CT alone. METHODS: Multiplanar CT in three orthogonal planes was used to evaluate 94 cases of SAH. Two investigators independently evaluated each imaging plane for focal thick SAH with mass effect, intracerebral hemorrhage, focal edema, filling defect, subdural hemorrhage, and dominant intraventricular hemorrhage. Also, rupture site was qualitatively identified by combining these variables in each plane and combination of three planes. DSA served as the gold standard to locate the rupture sites. RESULTS: Interobserver agreement was k 0.60 to 0.79 for axial, k 0.43 to 0.86 for coronal and k 0.43 to 0.74 for sagittal planes. Good to substantial agreement was observed for the localization of rupture site in three planes (focal SAH with mass effect - k 0.78 to 0.85; filling defect - k 0.95 to 1.0; intracerebral hemorrhage - k 1.0; focal edema k 1.0; subdural hemorrhage - k 0.61 to 0.83). Dominant intraventricular hemorrhage revealed significant association with DSA to locate ruptured aneurysms (Fisher's exact test - Pr < = P (< 0.001)). With non-missing data, frequency of correct ratings to locate rupture site was 66/67 (99%) in axial plane, 59/66 (89%) in coronal plane, 64/67 (96%) in sagittal plane and 77/77 (100%) in combined 3 planes. CONCLUSIONS: Multiplanar CT head is more successful than axial plane CT alone for the localization of aneurysm rupture sites in SAH.

Neuroradiologic timing of intracranial hemorrhage in abusive head trauma.

Determining the timing of intracranial injuries in general, and abusive head trauma (AHT) in particular, is important to the care of children with traumatic brain injury. Additionally, identifying the time of the injury provides important information as to who might have, and who did not, inflict the trauma. Understanding the appearance and evolution of intracranial findings on neuroimaging has been an important factor in assessing the time of the injury. However, a number of studies in the last two decades have both suggested greater uncertainty about the reliability of this process and advanced our knowledge in this area. In this review, the authors consider the biophysical factors that contribute to the appearance and evolution of intracranial hemorrhage and, in particular, subdural hemorrhage (SDH). The traditional view of SDH is predicated largely on prior studies of intracerebral hemorrhage, although a number of variables make this comparison untenable. Moreover, more recent studies have suggested a number of factors that could alter the density (CT) or signal intensity (MRI) and produce mixed density/intensity SDH. These factors need to be considered in interpreting neuroimaging studies. A number of these recent studies evaluating serial neuroimaging in children with AHT have modified our understanding of intracranial hemorrhage and its evolution in this context. Taken together, the studies to date, having important limitations, provide only broad ranges over which to time injuries. The authors conclude that neuroimaging studies at this time are not likely, in isolation, to be able to accurately pinpoint a specific time of injury; rather, neuroimaging can only provide a range of possible times and should instead be used as a means to supplement or corroborate timing based on clinical presentation and other imaging findings.

Neutrophil-induced ferroptosis promotes tumor necrosis in glioblastoma progression.

Tumor necrosis commonly exists and predicts poor prognoses in many cancers. Although it is thought to result from chronic ischemia, the underlying nature and mechanisms driving the involved cell death remain obscure. Here, we show that necrosis in glioblastoma (GBM) involves neutrophil-triggered ferroptosis. In a hyperactivated transcriptional coactivator with PDZ-binding motif-driven GBM mouse model, neutrophils coincide with necrosis temporally and spatially. Neutrophil depletion dampens necrosis. Neutrophils isolated from mouse brain tumors kill cocultured tumor cells. Mechanistically, neutrophils induce iron-dependent accumulation of lipid peroxides within tumor cells by transferring myeloperoxidase-containing granules into tumor cells. Inhibition or depletion of myeloperoxidase suppresses neutrophil-induced tumor cell cytotoxicity. Intratumoral glutathione peroxidase 4 overexpression or acyl-CoA synthetase long chain family member 4 depletion diminishes necrosis and aggressiveness of tumors. Furthermore, analyses of human GBMs support that neutrophils and ferroptosis are associated with necrosis and predict poor survival. Thus, our study identifies ferroptosis as the underlying nature of necrosis in GBMs and reveals a pro-tumorigenic role of ferroptosis. Together, we propose that certain tumor damage(s) occurring during early tumor progression (i.e. ischemia) recruits neutrophils to the site of tissue damage and thereby results in a positive feedback loop, amplifying GBM necrosis development to its fullest extent.

Dilated Epidural Venous Plexus Causing Radiculopathy: A Report of 2 Cases and Review of the Literature.

BACKGROUND: A dilated epidural venous plexus (DEVP) is a rare cause of radiculopathy, back pain, cauda equina syndrome, and other neurological symptoms. This vascular mass can be secondary to inferior vena cava obstruction, portal hypertension, vascular agenesis, and hypercoagulable states. Although rare, DEVP should be considered in the differential diagnosis for patients who present with lumbar radiculopathy. CASE DESCRIPTION: We present 2 cases involving patients with lumbar DEVP as well as a literature review of the role of hypercoagulability, vascular anatomy, and inferior vena cava thrombosis in the development of DEVP. The first patient had a history of recurrent deep vein thrombosis, systemic lupus erythematosus, and antiphospholipid syndrome. The diagnosis of DEVP was determined after intraoperative biopsy. The patient reported symptom resolution at her 6-month postoperative appointment. The second patient developed DEVP associated with Klippel-Trenaunay syndrome. She presented with back pain and leg weakness, and DEVP was diagnosed via magnetic resonance imaging. A neurosurgeon is currently following the patient. We believe this is the first case of Klippel-Trenaunay syndrome associated with DEVP. CONCLUSIONS: If a patient presents with an enhancing epidural lesion on magnetic resonance imaging and neurological symptoms, DEVP should be considered in the differential diagnosis. Additionally, a search for inferior vena cava thrombosis should be performed as well as risk factors for venous hypertension and hypercoagulable states.

Susceptibility-weighted imaging of retinal hemorrhages in abusive head trauma.

BACKGROUND: Retinal hemorrhages are one of the most important supportive evidences for abusive head trauma (AHT). Susceptibility-weighted imaging (SWI) is highly suited to identify various forms of intracranial hemorrhage in AHT. However its utility in imaging retinal hemorrhage is not well established. OBJECTIVE: SWI is a sensitive sequence for identifying retinal hemorrhage on MRI. MATERIALS AND METHODS: In this retrospective analysis, 26 consecutive infants and young children with a suspected admission diagnosis of AHT underwent indirect ophthalmoscopy and brain MRI protocol for AHT along with SWI. Brain susceptibility-weighted images of 14 age-matched children were used as controls. For detecting retinal hemorrhage, susceptibility-weighted images of patients and controls were reviewed randomly and independently by two neuroradiologists who were blinded to the history and ophthalmology findings. A pediatric ophthalmologist graded the indirect ophthalmoscopy images. RESULTS: A diagnosis of AHT was confirmed in all 26 cases from a multidisciplinary meeting. Indirect ophthalmoscopy images were available in 21 cases. Ophthalmoscopy was positive for retinal hemorrhage in the right eye in 18 cases (85.7%) and in the left eye in 16 cases (76.2%). On SWI, retinal hemorrhage was identified in the right eye in 9/21 cases (42.8%) and in the left eye in 8/21 cases (38.1%) of AHT. Analysis of SWI in 21 cases of AHT demonstrated a sensitivity of 50%, specificity of 100%, positive predictive value of 100% and negative predictive value of 32% for detecting retinal hemorrhage. CONCLUSION: SWI is moderately sensitive and highly specific for identifying retinal hemorrhage in AHT. Further studies are needed to identify steps to improve the efficiency of SWI in detecting retinal hemorrhage.

Pericallosal Lipoma and Cortical Dysplasia Masquerading as a Glioma.

Intracranial lipomas represent approximately 1% of intracranial lesions generally felt to represent the abnormal persistence of the meninx primitiva and are commonly accompanied by various developmental brain abnormalities. We report a case of midline intracranial lipoma and evolving frontal lobe fluid-attenuated inversion recovery (FLAIR) abnormality concerning for glial neoplasm in a patient with intractable epilepsy. Our case shows evolving magnetic resonance imaging (MRI) features over two decades raising suspicion for low-grade neoplasm which was ultimately found to represent cortical dysplasia.

Neuroleukemiosis: Two Case Reports.

Extramedullary tumors composed of myeloblasts or monoblasts can present in various locations. Patients with a history of acute myeloid leukemia (AML) can present with neuropathic pain and no evidence of relapse of their leukemia. Neuroleukemiosis is a form of extramedullary tumor present in the peripheral nervous systems (PNS) of leukemia patients. We report two AML patients who were in remission and later presented with neurological symptoms due to neuroleukemiosis with negative bone marrow biopsies.

A Comparison of Magnetic Resonance Angiography Techniques for the Evaluation of Intracranial Aneurysms Treated With Stent-assisted Coil Embolization.

AIM: To identify the effective magnetic resonance angiography (MRA) technique to monitor intracranial aneurysms treated with stent-assisted coiling. MATERIALS AND METHODS: Retrospective analysis of various MRA techniques was performed in 42 patients. Three neuroradiologists independently compared non-contrast time of flight (ncTOF) MRA of the head, contrast-enhanced time of flight (cTOF) MRA of the head and dynamic contrast-enhanced MRA (CEMRA) of the head and neck or of the head. Digital subtraction angiography (DSA) was available for comparison in 32 cases. Inter-rater agreement (kappa statistic) was assessed. RESULTS: Artifactual in-stent severe stenosis or flow gap was identified by ncTOF MRA in 23 of 42 cases (55%) and by cTOF MRA in 23 of 38 cases (60%). DSA excluded in-stent stenosis or occlusion in all 32 cases. No difference was noted between ncTOF and cTOF in the demonstration of neck remnants or residual aneurysms in three cases each. CEMRA of the head and neck or of the head was rated superior to ncTOF and cTOF MRA by all three investigators in seven out of eight cases. In one case, all three techniques demonstrated signifcant artifacts due to double stent placement during coiling. The kappa statistic revealed 0.8 agreement between investigators. CONCLUSIONS: In the assessment of stent-assisted coiling of intracranial aneurysm, both ncTOF and cTOF MRA show similar results. CEMRA tends to show better flow signals in stent and residual aneurysm.

Diffuse Subarachnoid Hemorrhage Secondary to Cerebral Venous Sinus Thrombosis.

BACKGROUND: Aneurysmal rupture accounts for the majority of nontraumatic subarachnoid hemorrhage (SAH). Increasingly recognized is the occurrence of nontraumatic convexity SAH unaccounted for by aneurysmal rupture. CASE REPORT: These presentations require consideration of rare but clinically significant sources of SAH. We report a patient presenting with prolonged mild headaches and acute onset of seizure like activity found to have diffuse subarachnoid hemorrhage and extensive dural venous sinus thrombosis involving the superior sagittal sinus and right transverse-sigmoid sinuses. CONCLUSIONS: There are few reported cases of SAH secondary to dural sinus thrombosis; however most of these are convexity hemorrhage. Sinus thrombosis presenting as diffuse SAH is extremely rare, as is showcased in this report.

Magnetic resonance characteristics and susceptibility weighted imaging of the brain in gadolinium encephalopathy.

BACKGROUND AND PURPOSE: To report the brain imaging features on magnetic resonance imaging (MRI) in inadvertent intrathecal gadolinium administration. METHODS: A 67-year-old female with gadolinium encephalopathy from inadvertent high dose intrathecal gadolinium administration during an epidural steroid injection was studied with multisequence 3T MRI. RESULTS: T1-weighted imaging shows pseudo-T2 appearance with diffusion of gadolinium into the brain parenchyma, olivary bodies, and membranous labyrinth. Nulling of cerebrospinal fluid (CSF) signal is absent on fluid attenuation recovery (FLAIR). Susceptibility-weighted imaging (SWI) demonstrates features similar to subarachnoid hemorrhage. CT may demonstrate a pseudo-cerebral edema pattern given the high attenuation characteristics of gadolinium. CONCLUSION: Intrathecal gadolinium demonstrates characteristic imaging features on MRI of the brain and may mimic subarachnoid hemorrhage on susceptibility-weighted imaging. Identifying high dose gadolinium within the CSF spaces on MRI is essential to avoid diagnostic and therapeutic errors.

Hemorrhage in the Wall of Pyogenic Brain Abscess on Susceptibility Weighted MR Sequence: A Report of 3 Cases.

Background and Purpose. In pyogenic brain abscess, hemorrhage in the walls is considered exceptional. Recently, hemorrhagic changes in the walls of pyogenic abscess have been demonstrated on susceptibility weighted imaging with 3T MRI. Here, we report hemorrhagic changes in the walls of pyogenic brain abscess on susceptibility weighted imaging with 1.5T MRI. Method. MRI of brain was done using 1.5T MRI with diffusion weighted sequence, susceptibility weighted sequence, and other standard sequences in 3 consecutive cases of pyogenic brain abscess. Stereotactic biopsy and cultures were obtained in 2 cases. One case was treated empirically with antibiotics. Results. Susceptibility sequence demonstrated hemorrhage in the wall of brain abscess in all three cases. All three cases also demonstrated restricted diffusion on diffusion weighted imaging. Conclusion. Susceptibility weighted imaging can demonstrate hemorrhagic changes in the walls of pyogenic brain abscess on 1.5T MRI. Presence of hemorrhage in the walls of ring enhancing lesions should not automatically lead to a diagnosis of tumor.

Sensitivity of 3D Gradient Recalled Echo Susceptibility-Weighted Imaging Technique Compared to Computed Tomography Angiography for Detection of Middle Cerebral Artery Thrombus in Acute Stroke.

We aimed at comparing the sensitivity of magnetic resonance (MR) susceptibility-weighted imaging (SWI) with computed tomography angiography (CTA) in the detection of middle cerebral artery (MCA) thrombus in acute stroke. Seventy-nine patients with acute MCA stroke was selected using our search engine software; only the ones showing restricted diffusion in the MCA territory on diffusion-weighted images were included. We finally selected 35 patients who had done both MRI (including SWI) and CTA. Twenty random subjects with completely normal MRI (including SWI) exam were selected as control. Two neuroradiologists (blinded to the presence or absence of stroke) reviewed the SW images and then compared the findings with CT angiogram (in patients with stroke). The number of MCA segments showing thrombus in each patient was tabulated to estimate the thrombus burden. Thrombus was detected on SWI in one or more MCA segments in 30 out of 35 patients, on the first review. Of the 30, SWI showed thrombus in more than one MCA segments in 7 patients. CTA depicted branch occlusion in 31 cases. Thrombus was seen on both SWI and CTA in 28 patients. Thrombus was noted in two patients on SWI only, with no corresponding abnormality seen on CTA. Two patients with acute MCA showed no vascular occlusion or thrombus on either CTA or SWI. Only two case of false-positive thrombus was reported in normal control subjects. Susceptibility-weighted images had sensitivity and specificity of 86% and 90% respectively, with positive predictive value 94%. Sensitivity was 86% for SWI, compared with 89% for CTA, and this difference was statistically insignificant (P>0.05). Of all the positive cases on CTA (31) corresponding thrombus was seen on SWI in 90% of subjects (28 of 31). Susceptibility-weighted imaging has high sensitivity for detection of thrombus in acute MCA stroke. Moreover, SWI is a powerful technique for estimation of thrombus burden, which can be challenging on CTA.

Transient leukoencephalopathy after intrathecal methotrexate mimicking stroke.

Methotrexate (MTX) is an indispensable antimetabolite for the treatment of oncological and immunological disorders in all age groups. It can be administrated intravenously as well as intrathecally and may be used alone or in combination with other drugs. Chronic leukoencephalopathy is a well-known side effect of MTX, especially in conjunction with intrathecal administration. However, acute neurotoxicity with confusion, disorientation, seizures, and focal deficits may also be seen. This can clinically mimic stroke with restricted diffusion on MRI. However, unlike stroke, there is resolution of clinical and imaging findings within 1-4 weeks. We report two cases of transient leukoencephalopathy following intrathecal methotrexate, with complete clinical and radiological resolutions on follow-up.