Atherosclerotic Carotid Plaques: Multimodality Imaging with Contrast-enhanced Ultrasound, Computed Tomography, and Magnetic Resonance Imaging.

INTRODUCTION: The imaging of carotid plaques has undergone a paradigm shift increasing importance being given to plaque characterization. Patients with "vulnerable" plaques are more prone to develop future neurovascular events. PURPOSE: The purpose of this study is to analyze the role of multimodality imaging techniques in the assessment of carotid atherosclerotic plaques. MATERIALS AND METHODS: Twenty-six patients were prospectively enrolled in the study. Patients underwent multidetector computed tomography (CT) angiography, ultrasound, contrast-enhanced ultrasound, and high-resolution magnetic resonance imaging (MRI) of the carotid arteries with special emphasis on the carotid bifurcation. RESULTS: The mean age of patients was 65.41 years. Twenty-one were males. Plaque neovascularization was seen in 10 of the 18 plaques studied (55.56%). Based on the predominant components of the plaque, plaques were characterized as lipid (3), lipid with recent hemorrhage (1), fibrous (7), fibrofatty (4), fibrofatty with some hemorrhagic components (3), and recent hemorrhage (2). CONCLUSIONS: Together, contrast-enhanced ultrasound, CT, and MRI provide complete information about the plaque characteristics.

Correlation between anatomic landmarks and fMRI in detection of the sensorimotor cortex in patients with structural lesions.

BACKGROUND: Structural lesions in/near the sensorimotor cortex may cause distortion/obscuration of the anatomic landmarks. PURPOSE: To compare the localization of the sensorimotor cortex using anatomical landmarks and fMRI in the clinical setting in patients with structural lesions in/near the central sulcus. MATERIAL AND METHODS: We analyzed the anatomic and fMRI data of 68 consecutive patients (42 tumors, 15 gliotic lesions, 11 focal cortical dysplasias [FCD]) who underwent MRI to assess the relationship of these lesions to the sensorimotor cortex. Anatomical data was analyzed on conventional two- and three-dimensional sequences. BOLD fMRI was performed with block design hand/leg or lip movement paradigm and general linear model was used for detecting the activated cortex. fMRI was considered as a valid method for identifying the sensorimotor cortex based on previously reported literature. RESULTS: The sensorimotor cortex could not be identified with anatomical landmarks in 9/68 (13.2%) patients. fMRI detected activation in areas different from that predicted by anatomical landmarks in 11/68 (16.2%) cases. This occurred in 5/42 (11.9%) tumors, 6/15 (40%) gliotic lesions, and 0/11 (0%) FCDs. The kappa value for concordance between fMRI and anatomic landmarks was 0.883 overall, 1.0 for tumors, 0.721 for gliotic lesions, and in none of the patients with focal cortical dysplasias. CONCLUSION: In patients with lesions that obscure normal cerebral landmarks, fMRI supplies the information that is not available from the anatomic images. In patients with landmarks that can be recognized, the location of the rolandic cortex may be misjudged in some cases if functional imaging is not used. Anatomic landmarks may not correlate with the area of functional activation in gliotic lesions and tumors. Determining the risk of a postoperative neurologic defect from surgery is likely to be more reliable with functional imaging than with conventional anatomic imaging.

Neuroenteric cysts of the brain-comprehensive magnetic resonance imaging.

Neuroenteric cysts are developmental cysts that should be differentiated from other, more common non-neoplastic cysts as well as cystic neoplasms. While these lesions may have varied imaging findings, T1 hyperintense prepontine lesion due to mucinous/proteinaceous content is characteristic. Location and imaging characteristics aid in formulating the correct diagnosis of neuroepithelial/neuroenteric cysts. Magnetic resonance spectroscopy (MRS) has the specific finding of N-Acetyl Aspartate (NAA)-like peak at 2.02 ppm which is not seen in other cystic lesions. In this study, we aim to discuss the imaging findings of these lesions on conventional and advanced MRI findings and provide radiologic-pathologic correlation. We also briefly describe the pathogenesis, embryology and radiological differential diagnoses of these cysts.

Multimodality imaging of carotid atherosclerotic plaque: Going beyond stenosis.

Apart from the degree of stenosis, the morphology of carotid atherosclerotic plaques and presence of neovascularization are important factors that may help to evaluate the risk and 'vulnerability' of plaques and may also influence the choice of treatment. In this article, we aim to describe the techniques and imaging findings on CTA, high resolution MRI and contrast enhanced ultrasound in the evaluation of carotid atherosclerotic plaques. We also discuss a few representative cases from our institute with the related clinical implications.

Imaging signs in idiopathic intracranial hypertension: Are these signs seen in secondary intracranial hypertension too?

BACKGROUND: The purpose of this study was to evaluate the difference in the occurrence of the various "traditional" imaging signs of intracranial hypertension (IIH) on magnetic resonance imaging (MRI) in patients with idiopathic (IIH) and secondary intracranial hypertension. MATERIALS AND METHODS: In a retrospective analysis, the MRI findings of 21 patients with IIH and 60 patients with secondary intracranial hypertension (41 with tumors; 19 with intracranial venous hypertension) were evaluated for the presence or absence of various "traditional" imaging signs of IIH (perioptic nerve sheath distention, vertical buckling of optic nerve, globe flattening, optic nerve head protrusion and empty sella) using the Fisher's exact test. Odds ratios were also calculated. Statistical Package for the Social Sciences version 17.0 was used for statistical analysis. Subgroup analysis of the IIH versus tumors and IIH versus venous hypertension were performed. RESULTS: Optic nerve head protrusion and globe flattening were significantly associated with IIH. There was no statistically significant difference in the occurrence of rest of the findings. On subgroup analysis, globe flattening and optic nerve head protrusion occurred significantly more often in IIH than in tumors. However, there was no statistically significant difference in the occurrence of any of these findings in patients with IIH and venous hypertension. CONCLUSIONS: IIH is a diagnosis of exclusion. While secondary causes of raised intracranial pressure (ICP) have obvious clinical findings on MRI, some conditions like cerebral venous thrombosis may have subtle signs and differentiating between primary and secondary causes may be difficult. In the absence of any evident cause of raised ICP, presence of optic nerve head protrusion or globe flattening can suggest the diagnosis of IIH.

'Susceptibility sign' on susceptibility-weighted imaging in acute ischemic stroke.

BACKGROUND AND AIM: Acute intra-arterial thrombus produces susceptibility artifact on gradient echo images (susceptibility sign). Our aim was to study the sensitivity and specificity of the susceptibility sign in various major intracranial arteries on susceptibility-weighted imaging (SWI) in patients with acute stroke. We also compared it with the 'hyperintensity sign' on fluid-attenuated inversion recovery (FLAIR) and 'hyperdense artery sign' on computed tomography (CT) for middle cerebral artery (MCA) occlusion. MATERIALS AND METHODS: We have retrospectively studied 48 patients with ischemic stroke in various stages, due to intracranial arterial occlusions, for presence of 'hyperdense artery sign' (CT), 'hyperintense arterial sign' (FLAIR sequence) and 'susceptibility sign' (SWI). The sensitivity and specificity of each sign to detect intracranial arterial occlusion were calculated using the contrast-enhanced magnetic resonance (MR) angiogram as reference standard. RESULTS: The sensitivity and specificity of the 'susceptibility sign' for detecting the MCA occlusion were 77% and 100% respectively (10 of 13).The sensitivity of the 'susceptibility sign' for detecting anterior cerebral artery (ACA) occlusion was 50% (1 of 2), 66.6% for posterior cerebral artery (2 of 3) and 75% for basilar artery (3 of 4). All the vertebral artery occlusions showed 'susceptibility sign' (6 of 6). Overall sensitivity and specificity of the 'susceptibility sign' for all acute major intracranial arterial occlusions were 82% and 100% respectively. Only one of the two cases of subacute infarcts studied showed a positive susceptibility sign. None of the 11 chronic intracranial occlusions and seven internal carotid occlusions showed the sign intracranially. CONCLUSION: 'Susceptibility sign' is more sensitive in detecting the acute MCA thrombus as compared to 'hyperdense MCA sign' on CT and 'hyperintense artery' sign on FLAIR images. It also has high sensitivity and specificity for other intracranial acute arterial occlusions.

Embryonal tumor with multilayered rosettes: Two case reports with a review of the literature.

Embryonal tumor with multilayered rosettes (ETMR) is a well-recognized histopathological variant of primitive neurectodermal tumors of the central nervous system. This tumor depicts histopathological features that are common to both ependymoblastoma (EBL) and neuroblastoma. Here we report two pediatric cases of ETMR, one exhibiting dominant neuronal differentiation and the other with dominant glial differentiation, thereby expanding the previously known pathologic spectrum. The varying histological features, common morphologic diagnostic difficulties as well as variable postsurgical survival of this entity compared to similar embryonal tumors are highlighted.

Tumefactive demyelinating lesions: a clinicopathological correlative study.

Tumefactive demyelinating (TDL) lesions are focal zones of demyelination in the central nervous system and they often mimic the neuroimaging features of an intraxial neoplasm. In this report we describe the clinical, neuroimaging and neuropathological features of six cases of TDL. Only in two patients the neuroimaging features in MRI (magnetic resonance imaging) scans were suggestive of TDL while in the other four cases a diagnosis of glioma was suggested. In order to establish a confirmatory diagnosis neuronavigation/stereotactic biopsy was undertaken and the diagnosis of TDL was established in all six cases at histopathology. Two out of six patients did not respond to the conventional corticosteroid therapy and they were treated with plasma exchange. It is being concluded that neuronavigation biopsy, though provide only a small amount of tissue, and is extremely useful in making the diagnosis of TDL.

Tanycytic ependymoma of filum terminale: a case report.

Tanycytic ependymoma is an uncommon but well-recognized variant of ependymoma. Here we report a case of tanycytic ependymoma occurring at the region of filum terminale in a 44-year male who presented with low backache, bilateral lower limb weakness and urinary incontinence. MR imaging in this patient showed a lesion that was composed of solid and cystic components and was suggestive of ependymoma. The filum terminale region is an extremely unusual location for the occurrence of tanycytic ependymoma. To the best of our knowledge this is the third case of tanycytic ependymoma occurring in the filum terminale region.

Spontaneous intracranial hypo and hypertensions: an imaging review.

Cerebrospinal fluid (CSF) pressure changes can manifest as either intracranial hypertension or hypotension. The idiopathic forms are largely under or misdiagnosed. Spontaneous intracranial hypotension occurs due to reduced CSF pressure usually as a result of a spontaneous dural tear. Idiopathic intracranial hypertension (IIH) is a syndrome of elevated intracranial tension without hydrocephalus or mass lesions and with normal CSF composition. Neuroimaging plays an important role in excluding secondary causes of raised intracranial tension. As the clinical presentation is varied, imaging may also help the clinician in arriving at the diagnosis of IIH with the help of a few specific signs. In this review, we attempt to compile the salient magnetic resonance imaging findings in these two conditions. Careful observation of these findings may help in early accurate diagnosis and to provide appropriate early treatment.

Applications of 3D CISS sequence for problem solving in neuroimaging.

Three-dimensional (3D) constructive interference in steady state (CISS) is a gradient-echo MRI sequence that is used to investigate a wide range of pathologies when routine MRI sequences do not provide the desired anatomic information. The increased sensitivity of the 3D CISS sequence is an outcome of the accentuation of the T2 values between cerebrospinal fluid (CSF) and pathological structures. Apart from its well-recognized applications in the evaluation of the cranial nerves, CSF rhinorrhea and aqueduct stenosis, we have found the CISS sequence to be useful for the cisternal spaces, cavernous sinuses and the ventricular system, where it is useful for detecting subtle CSF-intensity lesions that may be missed on routine spin-echo sequences. This information helps in the management of these conditions. After a brief overview of the physics behind this sequence, we illustrate its clinical applications with representative cases and discuss its potential role in imaging protocols.

Clinical utility of susceptibility-weighted imaging in vascular diseases of the brain.

Susceptibility-weighted imaging (SWI) is a rapidly evolving technique that utilizes both the magnitude and phase information to obtain valuable information about susceptibility changes between tissues. SWI is very sensitive to the paramagnetic effects of deoxyhemoglobin. SWI plays an important role in the diagnostic evaluation and management of acute stroke. In addition, it also plays an important role in the imaging of patients with chronic arterial occlusion and in understanding the effects of chronic infarction, like incomplete infarction and cortical laminar necrosis. The hemodynamic status and oxygen extraction fraction can also be evaluated. SWI is useful in evaluating cerebral venous sinus thrombosis by demonstrating the hemorrhagic venous infarction and thrombus in the sinus and the cortical veins, as well as secondary phenomena like venous stasis in the form of engorged cortical and transmedullary veins and collateral slow flow. Low-flow vascular malformations that are not visualized well on conventional sequences are depicted in exquisite detail along with the venous components on SWI. SWI is used for evaluating cavernomas, developmental venous anomalies, telangiactasias, dural arteriovenous fistulas and the various components of arteriovenous malformations. It has also evolved as a noninvasive technique for evaluating various anomalies of the venous system without administering contrast. Vasculopathies and vasculitis are associated with cerebral microbleeds which are detected on SWI. On the basis of the additional information provided by SWI, it can be included in the routine brain imaging protocol.

Colloid cyst of the velum interpositum: a common lesion at an uncommon site.

BACKGROUND: Colloid cysts are typically located in the region of the anterior third ventricle in the proximity of foramen of Monro. Although 'endodermal cyst' has been identified in several regions of the brain, location of characteristic colloid cyst entirely within the confines of velum interpositum and outside the ventricles has not been reported earlier. CASE DESCRIPTION: We report a unique case of colloid cyst located in the region of velum interpositum in a 33-year-old patient with headache and seizures. Such a location of the colloid cyst has not been identified earlier in the literature. The literature on pathogenesis of colloid cysts in general is briefly reviewed. CONCLUSIONS: Colloid cyst located in the velum interpositum is reported. Such a location gives additional information on the pathogenesis of these lesions.