Browsing by Author "Radhakrishnan, V. V."
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Item Advanced MR imaging in Lhermitte-Duclos disease: moving closer to pathology and pathophysiology(NEURORADIOLOGY, 2007)Introduction Lhermitte-Duclos disease (LDD, dysplastic gangliocytoma) is an extremely rare cerebellar lesion of uncertain etiology. The debate as to whether it constitutes a neoplastic, malformative, or hamartomatous lesion is still continuing. In this report we explore the usefulness of susceptibility-weighted imaging (SWI), diffusion weighted imaging (DWI), perfusion imaging, and chemical shift imaging (CSI) in demonstrating the pathology and pathophysiology in two patients with LDD.Methods MR imaging of the brain and the cervicodorsal spine was performed on a 1.5-T scanner in a 47-year-old woman presenting with numbness and paresthesia of both upper and lower limbs, and in a 17-year-old male with right frontal headache associated with neck pain.Results Routine imaging in the first patient showed a leftside cerebellar mass with characteristic 'tiger-striped' thick folia associated with Chiari I malformation, tonsillar herniation and cervicodorsal syringomyelia and in the second patient a right cerebellar mass with similar findings. The SWI demonstrated the characteristic deep running veins between the folia, which is thought to be the cause for vascular contrast enhancement. Diffusion showed a T2 shine-through effect with mild increased diffusivity, and perfusion showed increase in relative cerebral blood volume, relative cerebral blood flow, and mean transit time in the lesion. MR spectroscopy demonstrated reduction in metabolites and a prominent lactate peak in both the patients. The pathological and pathophysiological significance of these findings is discussed.Conclusion MRI with the newer imaging capabilities can demonstrate the pathology and pathophysiology in Lhermitte-Duclos disease better. SWI helps in detecting the veins around the thickened folia.Item Alanine peak in central neurocytomas on proton MR spectroscopy(NEURORADIOLOGY, 2007)Introduction We present three consecutive patients with central neurocytoma in whom proton MRS demonstrated the presence of alanine.Materials and methods Three patients in the age range 24 to 30 years underwent MRI and proton MRS using a 1.5-T system. MRS was performed with the multivoxel PRESS sequence. All three patients underwent surgery and the diagnosis of central neurocytoma was established by histopathological examination and immunostaining.Results With an echo time of 135 ms glycine, high choline, small NAA and alanine were observed in all three patients.Conclusion Alanine may be observed in central neurocytomas as it is in meningiomas. Other spectral peaks such as those for glycine and NAA should help to identify this tumor correctly.Item Atypical clinical and imaging manifestation in neurocysticercosis(ANNALS OF INDIAN ACADEMY OF NEUROLOGY, 2011)A 20-year-old man presented with left-sided headache and seizures of three years duration. Conglomerate ring-enhancing lesions were seen in the first magnetic resonance imaging study. He was initially treated with anticonvulsants for two years. Because the symptoms and the lesions were persisting, antitubercular treatment was added. He was asymptomatic after antitubercular treatment despite persisting lesion. Lesion showed exuberant ring enhancement with increased perfusion. Because the lesion was persisting even after 24 months of antitubercular treatment, excision was considered. Lesionectomy was done and histopathology reported meningoencephalitis secondary to neurocysticercosis. The case report highlights the difficulty in differentiating cysticercosis from tuberculoma in patients from countries where both the conditions are endemic.Item Atypical fungal granuloma of the sphenoid wing(JOURNAL OF NEURORADIOLOGY, 2009)A 29-year-old immunocompetent patient presented with a 3-month history of headache and vomiting. Computed tomography (CT) and conventional magnetic resonance imaging (MRI) revealed a mass lesion in the right sphenoid wing. The conventional imaging findings were typical of meningioma. However, diffusion-weighted imaging (DWI), susceptibility-weighted imaging (SWI) and perfusion-weighted imaging (PWI) all revealed details that were unusual for a meningioma. DWI showed diffusion blackout, perfusion was not raised in PWI, and susceptibility effects were noted in SWI. Based on these findings, the possibility of granuloma was kept as the differential diagnosis. Histopathological examination of the lesion was suggestive of fungal granuloma. This case report highlights the importance of advanced neuroimaging techniques in differentiating meningioma and granuloma. (C) 2009 Elsevier Masson SAS. All rights reserved.Item Diagnostic approaches in patients with tuberculous pleural effusion(DIAGNOSTIC MICROBIOLOGY AND INFECTIOUS DISEASE, 2007)The conventional bacteriologic methods used for diagnosing pleural tuberculosis are less sensitive and time consuming. The objective of this study was to develop nonbacteriologic methods and to assess their potential utilities for the rapid diagnosis, especially in smear/culture-negative patients. One hundred forty patients with pleural effusion were investigated for tuberculous etiology by bacteriologic methods. Mycobacterium tuberculosis in the pleural fluid specimens was isolated in I I patients. To establish a tuberculous etiology in the remaining 129 patients, we performed the following assays: a) estimation of tuberculosis-associated glycolipid antigen (TBGL) by a modified indirect enzyme-linked inummosorbent assay (ELISA), b) an immunocytochemical method for the demonstration of TBGL antigen in the Cytospin smears, and c) detection of mycobacterial DNA by polymerase chain reaction (PCR). Estimation of TBGL antigen by ELISA showed 100% specificity and overall 85.5% sensitivity. Immunocytochemistry could be applied only in those samples with adequate number of macrophages. PCR carried sensitivity and specificity of 87% and 93%, respectively. Estimation of TBGL antigen in pleural fluid specimens by ELISA has a definite role in establishing tuberculous etiology, particularly in those patients in whom bacteriologic methods did not demonstrate M. tuberculosis and also in those in whom a distinction between tuberculous and nontuberculous etiology was not possible based on the clinical and radiologic features of the thorax. (c) 2007 Elsevier Inc. All rights reserved.Item Diagnostic Significance of Humoral Immune Responses to Recombinant Antigens of Mycobacterium tuberculosis in Patients with Pleural Tuberculosis(JOURNAL OF CLINICAL LABORATORY ANALYSIS, 2010)Mycobacterium tuberculosis bacilli are seldom demonstrated in tuberculous pleural effusion (TPE) by conventional bacteriological methods. In this study, an indirect enzyme-linked immunosorbent assay (ELISA) was developed to detect IgG against four mycobacterial recombinant antigens (ESAT-6, PlcA, HspX and Tb8.4) in 69 pleural fluids of patients with TPE and 71 patients with malignant pleural effusion. To increase the sensitivity of the assay, a multi-antigen cocktail containing all the above antigens were also used. IgG positivity in ELISA for PlcA, HspX, Tb8.4, ESAT-6 antigens and multi-antigen complex were 49.3, 60.8, 49.3, 53.6 and 75.4% respectively. Each one of the above four antigens and their multi-antigen cocktail were highly specific in distinguishing tuberculous and malignant pleural effusion. This new generation immunoassay will serve as a useful marker for the diagnosis of pleural tuberculosis patients in whom M. tuberculosis bacilli were not demonstrated by bacteriological methods. J. Clin. Lab. Anal. 24:283-288, 2010. (C) 2010 Wiley-Liss, Inc.Item Diffusion tensor mode in imaging of intracranial epidermoid cysts: one step ahead of fractional anisotropy(NEURORADIOLOGY, 2009)The signal characteristics of an epidermoid on T2-weighted imaging have been attributed to the presence of increased water content within the tumor. In this study, we explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in knowing the microstructural anatomy of epidermoid cysts.DTI was performed in ten patients with epidermoid cysts. Directionally averaged mean diffusivity (D (av)), exponential diffusion, and DTM-like fractional anisotropy (FA), diffusion tensor mode (mode), linear (CL), planar (CP), and spherical (CS) anisotropy were measured from the tumor as well as from the normal-looking white matter.Epidermoid cysts showed high FA. However, D (av) and exponential diffusion values did not show any restriction of diffusion. Diffusion tensor mode values were near -1, and CP values were high within the tumor. This suggested preferential diffusion of water molecules along a two-dimensional geometry (plane) in epidermoid cysts, which could be attributed to the parallel-layered arrangement of keratin filaments and flakes within these tumors.Thus, advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.Item Disseminated necrotizing leukoencephalopathy following low-dose oral methotrexate(EUROPEAN JOURNAL OF NEUROLOGY, 2007)Leukoencephalopathy is a recognized complication with intrathecal or intravenous methotrexate (MTX). We report a 59-year-old lady who developed MTX leukoencephalopathy with long-term low-dose oral MTX. She developed posterior leukoencephalopathy (PLE) that initially was reversible on discontinuation of oral MTX. Four months later, she developed disseminated necrotizing leukoencephalopathy (DNL), and was left with devastating neurological deficits. The sequential conventional magnetic resonance imaging (MRI), diffusion weighted imaging (DWI), MR perfusion (MRP) and MR spectroscopic (MRS) changes are highlighted in this report. MRP and MRS showed more wide spread abnormalities than DWI. Stereotactic biopsy from the lesion revealed demyelination with macrophagic infiltration, pericapillary lymphomononucear aggregation,fibrinoid changes in the capillaries and neovascularization. Of the two cases of PLE with oral MTX reported in literature, one reversed clinically and radiologically with the discontinuation of MTX. To the best of our knowledge, this is the first reported case of DNL following oral MTX in the world literature.Item Embryonal tumor with multilayered rosettes: Two case reports with a review of the literature(NEUROLOGY INDIA, 2012)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.Item Fluid-fluid levels in cystic lumbosacral schwannomas: a report of three cases(SINGAPORE MEDICAL JOURNAL, 2009)Magnetic resonance imaging features of three benign cystic lumbosacral schwannomas, which showed multiple fluid-fluid levels, are described. One of the tumours showed bone destruction with fluid-fluid levels that closely mimicked an aneurysmal bone cyst. Pathological examination confirmed haemorrhage as the cause of fluid-fluid levels in the tumours. Though a rare finding, fluid-fluid levels with bone destruction can also be caused by nerve sheath tumours and hence must be included in the list of differential diagnoses of spinal tumours.Item Fungal infections of the central nervous system in HIV-negative patients: Experience from a tertiary referral center of South India(ANNALS OF INDIAN ACADEMY OF NEUROLOGY, 2010)Objective: To describe the clinical, radiological, and cerebrovascular fluid (CSF) findings and the outcome of microbiologically or histopathologically proven fungal infections of the central nervous system (CNS) in HIV-negative patients. Methodology and Results: We identified definite cases of CNS mycosis by screening the medical records of our institute for the period 2000-2008. The clinical and imaging details and the outcome were abstracted from the medical records and entered in a structured proforma. There were 12 patients with CNS mycosis (i.e., 2.7% of all CNS infections treated in this hospital); six (50%) had cryptococcal infection, three (25%) had mucormycosis, and two had unclassified fungal infection. Four (33%) of them had diabetes as a predisposing factor. The common presentations were meningoencephalitis (58%) and polycranial neuritis (41%). Magnetic resonance imaging revealed hydrocephalus in 41% and meningeal enhancement in 25%, as well as some unusual findings such as subdural hematoma in the bulbocervical region, carpeting lesion of the base of the skull, and enhancing lesion in the cerebellopontine angle. The CSF showed pleocytosis (66%), hypoglycorrhachia (83%), and elevated protein levels (100%). The diagnosis was confirmed by meningocortical biopsy (in three cases), paranasal sinus biopsy (in four cases), CSF culture (in three cases), India ink preparation (in four cases), or by cryptococcal polysaccharide antigen test (in three cases). Out of the ten patients for whom follow-up details were available, six patients recovered with antifungal medications (amphotericin B, 1 mg/kg/day for the minimum period of 6 weeks) and/or surgical treatment. Four patients expired (only one of them had received antifungal therapy). Conclusions: Most patients with CNS mycosis recover with appropriate therapy, but the diagnosis and management of these rare infections remains a challenge to clinicians.Item Germinoma of medulla(NEUROLOGY INDIA, 2010)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.Item Glioma grading: sensitivity, specificity, positive and negative predictive values of diffusion and perfusion imaging(JOURNAL OF NEURO-ONCOLOGY, 2009)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.Item Intracranial Intradural Aneurysmal Bone Cyst: A Unique Case(PEDIATRIC NEUROSURGERY, 2009)Aneurysmal bone cyst (ABC) of the skull is exceedingly rare. We report a unique case of an intradural ABC without bone involvement presenting with raised intracranial pressure. The patient was a 14-year-old boy who presented with headache, vomiting and right focal seizure. Imaging showed a large multicystic left frontal lesion without any evidence of bone involvement. The lesion adherent to an intact sphenoid wing dura was completely excised. The histopathology report was consistent with an ABC. This case represents the first report of an ABC without involvement of the skull bones or any evidence of dural erosion. The possible mechanism of origin at this unusual location is hypothesized. Copyright (C) 2009 S. Karger AG, BaselItem Intratumoral microhemorrhages on T2*-weighted gradient-echo imaging helps differentiate vestibular schwannomas from meningioma(AMERICAN JOURNAL OF NEURORADIOLOGY, 2008)BACKGROUND AND PURPOSE: Vestibular schwannomas (VS may be difficult to differentiate from cerebellopontine angle (CPA) meningiomas. Demonstration of microhemorrhages in VS on T2*-weighted gradient-echo (GRE) sequences may have potential value to differentiate VS from CPA meningiomas.MATERIALS AND METHODS: In this prospective study of 20 patients, MR imaging was performed with T2*-weighted GRE in addition to all basic sequences. Histopathologic examination was performed after surgery. Intratumoral hemosiderin was confirmed by pigment staining.RESULTS: There were 15 patients in the VS group with 16 VS and 5 in the meningioma group with 5 posterior fossa meningiomas. Fourteen of the 16 VS and all 5 meningiomas were treated surgically and were confirmed on histopathologic examination. T2*-weighted GRE identified microhemorrhages on T2*-weighted sequence in 15 (93.75%) of the 16 VS. CT excluded calcification in all VS. T2-weighted turbo spin-echo (TSE) and fluid-attenuated inversion recovery (FLAIR) images recognized microhemorrhages in 2 cases. Pigment staining confirmed hemosiderin in all 14 surgically treated VS, and none of the meningiomas showed microhemorrhages on MR imaging. For the detection of microhemorrhages, T2*-weighted GRE showed a sensitivity of 93.8%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 83.3%. The sensitivity of T2 TSE and FLAIR for microhemorrhage was 12.5%. The Fisher exact test showed a statistically significant difference in the differentiation of VS from meningioma on the basis of detection of microhemorrhages (P < .01).CONCLUSION: Most VS demonstrate microhemorrhages on T2*-weighted GRE. This finding is useful to differentiate VS from CPA, meningiomas. T2*-weighted GRE should be used as a basic sequence to evaluate CPA tumors. Identification of microhemorrhages may have the potential to assess the aggressive biologic behavior of VS.Item Mean intensity curve on dynamic contrast-enhanced susceptibility-weighted perfusion MR imaging - review of a new parameter to differentiate intracranial tumors(JOURNAL OF NEURORADIOLOGY, 2011)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. (C) 2011 Elsevier Masson SAS. All rights reserved.Item Meckel's cave tuberculoma with unusual infratemporal extension(JOURNAL OF NEUROIMAGING, 2007)The authors describe a rare case of intracranial tuberculoma of the Meckel's cave and cavernous sinus with extension into the infratemporal fossa causing widening of the foramen ovale and adjacent bone destruction. The rarity of the lesion and the unusual extension of the lesion are presented with a brief review of literature.Item Multifocal desmoplastic noninfantile astrocytoma(JOURNAL OF NEURORADIOLOGY, 2008)This is a report of a case of multifocal desmoplastic astrocytoma in an 11-year-old child in which we describe the MRI findings and discuss the possible mechanism of its development. The MRI appearances in our case support the view that the tumor is primarily of teptomeningeal or superficial cortical origin, with cystic formation secondary to entrapment of cerebrospinal fluid. The question of whether or not the lesions are metastases or metachronous lesions is also discussed. Desmoplastic astrocytoma at a noninfantile age is extremely rare: only four cases have been reported in the literature so far. Even more unusual is the presence of this lesion in multiple locations at the initial presentation. (C) 2008 Elsevier Masson SAS. All rights reserved.Item Primary diffuse leptomeningeal gliomatosis(JOURNAL OF NEURORADIOLOGY, 2009)A 20-year-old woman with a history of seizures presented symptoms of walking difficulties for the past six months. Clinical examination was suggestive of a craniovertebral junction anomaly. A cerebrospinal fluid study showed mild protein elevation with no evidence of an infective pathology. Craniospinal MRI revealed diffuse nodular leptomeningeal enhancement of the brain and spinal cord. Histopathological examination was suggestive of a low-grade glioma, and the patient was diagnosed with primary diffuse leptomeningeal gliomatosis. So far, the patient has survived for more than 110 months without aggressive therapy. (C) 2008 Elsevier Masson SAS. All rights reserved.Item Rhabdoid and papillary meningioma with leptomeningeal dissemination(JOURNAL OF NEURORADIOLOGY, 2008)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. (C) 2008 Elsevier Masson SAS. All rights reserved.