Quantification of diffusion and anisotropy in intracranial epidermoids using diffusion tensor metrics and p: q tensor decomposition.

PURPOSE: To quantitatively evaluate the diffusion tensor metrics p, q, L and fractional anisotropy in intracranial epidermoids in comparison with normal white matter in the splenium of the corpus callosum. METHODS: This retrospective study included 20 consecutive patients referred to our institute. All patients had a magnetic resonance imaging (MRI) study on a 1.5-Tesla MR system. A spin-echo echo-planar DTI sequence with diffusion gradients along 30 non-collinear directions was performed. The eigen values (λ1, λ2, λ3) were computed for each voxel and, using p: q tensor decomposition, the DTI metrics p, q and L-values and fractional anositropy (FA) were calculated. The region of interest (ROI) (6 pixels each) was placed within the lesion in all the cases and in the splenium of the corpus callosum. RESULTS: The mean FA in the lesion and splenium were 0.50 and 0.88 respectively, with a statistically significant difference between them (P<0.01). On p: q tensor decomposition, the mean p-value in the epidermoid was 1.55±0.24 and 1.35±0.20 in the splenium; the mean q-values in the epidermoid was 0.67±0.13 and 1.27±0.17 in the splenium; the differences were statistically significant (P=0.01 and <0.01 respectively). The significant difference between p- and q-values in epidermoids compared with the splenium of callosum was probably due to structural and orientation differences in the keratin flakes in epidermoids and white matter bundles in the callosum. However, no significant statistical difference in L-values was noted (P=0.44). CONCLUSION: DTI metrics p and q have the potential to quantify the diffusion and anisotropy in various tissues thereby gaining information about their internal architecture. The results also suggest that significant differences of DTI metrics p and q between epidermoid and the splenium of the corpus callosum are due to the difference in structural organization within them.

Varying clinical and imaging outcomes in patients with spontaneous thrombosis of vein of Galen malformation--a report of two cases.

BACKGROUND: Vein of Galen malformations are rare congenital intracranial vascular malformations. The pathophysiological consequences usually manifest as high-output cardiac failure and neurological symptoms secondary to cerebral venous congestion and abnormal CSF flow. Management of these patients is complex. Indications and time to intervene are decided depending upon the age of child, clinical presentation, and multisystemic neonatal scores. Many of these children presenting early and who are not in cardiac failure are expectantly followed up. Spontaneous thrombosis of the vein of Galen malformation is a rare occurrence in these as such rare vascular malformations. METHODS: This review reports two cases of spontaneous thrombosis of the vein of Galen malformations with varying clinical as well as imaging outcomes. Possible pathophysiologic mechanisms are discussed with review of literature. RESULTS: This report highlights the importance of vigilant clinical and imaging follow-up even after spontaneous thrombosis in the vein of Galen malformations.

Diffusion tensor imaging and tractography of the human language pathways: moving into the clinical realm.

The functional correlates of anatomical derangements are of interest to the neurological clinician. Diffusion tensor tractography (DTT) is a relatively new tool in the arsenal of functional neuroimaging, by which to assess white matter tracts in the brain. While much import has been given to tracking corticospinal tracts in neurological disease, studying language pathway interconnections using DTT has largely remained in the research realm. Hardware and software advances have allowed this tool to ease into clinical practice, with several radiologists, neurologists, and neurosurgeons now familiar with its applications. DTT images, although visually appealing, are founded in mathematical equations and assumptions, and require a more than basic understanding of principles and limitations before they can be integrated into routine clinical practice. Cognitive pathways like that of language, that are normally hard to assess and especially more so when pathologically affected, have been at the receiving end of several opposing and often controversial hypotheses, and the past decade has seen the clarification, validation or rejection of several of these by the in vivo charting of functional connectivity using DTT. The focus of this review is to illustrate DTT of the language pathways with emphasis on practical considerations, clinical applications, and limitations.

Intracranial ewings sarcoma/peripheral primitive neuroectodermal tumor.

Central nervous system primitive neuroectodermal tumours (CNS PNET) are aggressive embryonal tumours composed of undifferentiated or poorly differentiated neuroepithelial cells seen in the pediatric age group. This is rare and only a handful of cases of ES/pPNET in CNS are reported. We report such a case in a 3 year old child. Reporting of more such cases is needed to better define these rare tumours of the dura.

Implicating the long styloid process in cervical carotid artery dissection.

INTRODUCTION: To look for the presence and strength of association of cervical carotid artery dissection (CCAD) with a long styloid process. METHODS: This case-control analysis included 35 patients with 37 affected carotid arteries. CT angiograms of these patients were analyzed by two raters blinded to clinical and radiological diagnosis. Parameters assessed were styloid process length, its proximity to the cervical internal carotid artery, and its medial and anterior angulations. The same parameters were assessed in 70 CT angiograms in age and sex matched controls. RESULTS: Interrater correlations were 0.87, 0.40, 0.71, and 0.79 for styloid process length, contact distance, medial angulation, and anterior angulation, respectively. The mean styloid process length on the affected side was significantly more than on the contralateral side (37.8 vs. 34.6 mm, p = 0.006). There were also significant length and contact distance differences between the styloid processes ipsilateral to dissection and ipsilateral styloid processes of controls (38.9 vs. 36.2 mm, p = 0.05 and 3.1 vs. 5.0 mm, p = 0.05, respectively). There were increasing odds ratios (OR) for dissection with increasing styloid process length, with OR of 4.36 (95% CI = 1.04 to 18.4, p = 0.04) for length more than 50 mm. ORs for dissection increased with decreasing contact distance, with OR for distances less than 5 mm being 7.58 (95% CI = 0.93 to 62.1, p = 0.06). There was no significant association of CCAD with angulation of the styloid process. CONCLUSION: Length and contact distance of the styloid process are risk factors for CCAD, suggesting mechanical impingement.

Susceptibility weighted imaging in the evaluation of movement disorders.

Movement disorders are neurodegenerative disorders associated with abnormalities of brain iron deposition. In this presentation, we aim to describe the role of susceptibility weighted imaging (SWI) in the imaging of patients with movement disorders and differentiate between the various disorders. SWI is a high-resolution, fully velocity-encoded gradient-echo magnetic resonance imaging (MRI) sequence that consists of using both magnitude and phase information. We describe briefly the physics behind this sequence and the post-processing techniques used. The anatomy of the midbrain and basal ganglia in normal subjects on SWI is covered. A number of neurodegenerative disorders are associated with abnormal iron deposition, which can be detected due to the susceptibility effects.

An unusual cause for unruptured sinus of valsalva aneurysm.

Sinus of valsalva aneurysm is considered to be one of the rarest complications of inflammatory aortitis. Herewith, we are reporting a young male patient who presented to us with severe aortic regurgitation. On evaluation, he was found to have unruptured sinus of valsalva aneurysm. CT angiography and magnetic resonance imaging have shown value in the diagnosis of sinus of valsalva aneurysm.

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.

Advanced MRI in Rosai-Dorfman disease: correlation with histopathology.

Rosai-Dorfman disease is an idiopathic benign lymphoproliferative disorder that can, on rare occasions, cause intracranial or intraspinal lesions with non-specific features on conventional imaging. For this reason, its diagnosis is based on the classical pathological findings of histiocyte proliferation and emperipolesis. In this case report, we describe the imaging features of Rosai-Dorfman disease as visualized by newer types of MRI sequences, such as diffusion tensor imaging (DTI), susceptibility-weighted imaging (SWI) and perfusion-weighted imaging (PWI). In fact, combining the findings of conventional cross-sectional imaging with high fractional anisotropy (FA), a low apparent diffusion coefficient (ADC), mild blooming on SWI and decreased perfusion can help to make the diagnosis of Rosai-Dorfman disease. These newer tools can also be used to clarify the pathology of Rosai-Dorfman disease.

Mean intensity curve on dynamic contrast-enhanced susceptibility-weighted perfusion MR imaging--review of a new parameter to differentiate intracranial tumors.

Dynamic susceptibility contrast (DSC) perfusion imaging has been in clinical use for various indications, including characterization and grading of intracranial neoplasms. However, several technical factors can lead to pitfalls in image interpretation. This review discusses the extraction of T1 and T2* information from mean curve analysis of DSC perfusion imaging of various brain tumors, which provides further insights into tumor biology and, thus, may be useful in the differential diagnosis of such tumors. Indeed, by looking at the mean time-signal intensity curve from the tumor bed in addition to the rCBV maps, it is possible to obtain further inferences of capillary density and lesion leakiness. When dynamic contrast enhanced (DCE) T1 perfusion is not available, DSC perfusion with mean curve analysis appears to be a valid alternative for characterizing various brain neoplasms in a routine clinical setting.

Germinoma of medulla.

Germinoma occurring in the medulla oblongata is extremely rare. We report a case of primary intracranial germinoma arising in the medulla oblongata of a 24-year-old postpartum female who presented with progressive weakness of upper and lower limbs, seventh nerve palsy, and decreased palatal movements. Her MR imaging showed a heterointense mass lesion in the posterior portion of upper medulla, the histology of which was reported as germinoma. Germ cell tumors should be considered in the differential diagnosis of tumors occurring in the brain stem.

Glioma grading: sensitivity, specificity, positive and negative predictive values of diffusion and perfusion imaging.

PURPOSE: The purpose of our study was to determine the statistical significance of thresholds of relative cerebral blood volume (rCBV), apparent diffusion coefficient (ADC) and ADC ratios in grading cerebral gliomas. MATERIALS AND METHODS: In this retrospective study, 51 patients with histopathologically confirmed primary cerebral gliomas who had undergone conventional MR imaging, dynamic contrast-enhanced T2*-weighted perfusion MR imaging and diffusion MR imaging were included. A retrospective blinded analysis of the imaging findings including the perfusion and diffusion parameters was done. The rCBV measurements were obtained from regions of maximum perfusion. Minimum ADC values were obtained from the region of maximum hypointensity within the tumor and from the corresponding opposite white matter. Tumor grade determined with the two methods were then compared with the histopathologic grade. Mann-Whitney tests were performed to compare the DWI and PWI between tumor types. Receiver operating characteristic analyses were performed to determine optimum thresholds for tumor grading and also to calculate the sensitivity, specificity, PPV, and NPV for identifying high-grade gliomas. RESULTS: Statistical analysis demonstrated a threshold value of 2.91 for rCBV to provide sensitivity, specificity, PPV, and NPV of 94.7, 93.75, 90.0, and 96.8%, respectively, in determining high-grade gliomas. An ADC value of 98.50 mm(2)/s was defined as a threshold below which tumors were classified as high-grade gliomas and a sensitivity, specificity, PPV, and NPV of 90, 87.1, 81.81 and 93.10% respectively, were obtained. Significant differences were noted in the rCBV ratios, ADC and ADC ratios between low- and high-grade gliomas (P < 0.0001). CONCLUSION: Combining PWI and DWI with conventional MR imaging increases the accuracy of pre-operative imaging grading of glial neoplasms. The rCBV measurements had the most superior diagnostic performance in predicting glioma grade. Absolute ADC values or ADC ratios were also helpful in preoperative grading of gliomas. Threshold values can be used in a clinical setting to evaluate tumors preoperatively for histologic grade and provide a means for guiding treatment and predicting postoperative patient outcome.

Endovascular treatment of scalp cirsoid aneurysms.

BACKGROUND: Scalp is the most common site of soft tissue arteriovenous fistulae and surgical excision has been the primary mode of treatment. Endovascular treatment has evolved as an alternative to the surgery. AIMS: To evaluate the effectiveness of percutaneous direct-puncture embolization of cirsoid aneurysms. MATERIALS AND METHODS: From January 1995 to December 2004, 15 patients underwent percutaneous direct-puncture embolization of cirsoid aneurysms. Plain X-ray, computerized tomography scan and complete selective cerebral angiogram were done in all. Seven patients had forehead lesions, four had temporal and the remaining four patients had occipital region cirsoid aneurysms. Lesions were punctured with 21-gauge needle and embolized with 20-50% cyanoacrylate-lipiodol mixture. Circumferential compression was applied during injection. RESULTS: Post-embolization angiogram showed complete obliteration in 11 patients. The remaining four patients required adjunctive transarterial embolization with polyvinyl alcohol particles for complete lesion devascularization. Two patients had post procedure surgery for removal of disfiguring and hard glue cast. There were no major procedure-related complications. No patients had any recurrence in the follow-up. CONCLUSION: Percutaneous direct puncture embolization of cirsoid aneurysms is a safe and effective procedure. It can be effectively used as an alternative to surgery. Sometimes adjunctive transarterial embolization is also required to deal with deeper feeders.

Rhabdoid and papillary meningioma with leptomeningeal dissemination.

Rhabdoid meningioma is a rare variant of meningioma classified as grade III under the new World Health Organization (WHO) classification of brain tumors. Although this tumor is known for its aggressive behavior, dissemination into cerebral spinal fluid (CSF) is extremely rare. We report here a case of rhabdoid meningioma in a young man, operated on twice previously, who presented with multiple CSF areas of seeding in the brain and spinal cord. The imaging findings for this tumor, including diffusion and perfusion MR sequences, are highlighted. This particular histological subtype of meningioma has a poor prognosis and must be treated aggressively.