Browsing by Author "Thomas, B."

Now showing 1 - 14 of 14
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    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.
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    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.
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    Endovascular treatment of scalp cirsoid aneurysms
    (NEUROLOGY INDIA, 2008)
    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.
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    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.
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    Fluoroscopic-guided balloon dilatation and stenting in tracheal stenosis with metallic self-expandable stents and long-term follow-up results
    (AUSTRALASIAN RADIOLOGY, 2007)
    The purpose of this study was to assess the safety and long-term efficacy of self-expandable stents in the treatment of benign tracheal stenosis. Nine patients (seven men) with tracheal stenosis (including one with fistula) of varied cause were treated by fluoroscopically guided balloon dilatation and stenting with self-expandable metallic stents. The procedure was carried out under topical spray in eight patients and under general anaesthesia in one patient. The patients were followed up for a period ranging between 13 and 60 months. in eight of the nine patients, satisfactory positioning of the stent was achieved at the first instance, with immediate relief of dyspnoea. One patient with innominate artery aneurysm died 16 days after the procedure because of renal failure. At 1 month of follow up, six out of eight (75%) of our live patients were without any respiratory embarrassment. This dyspnoea-free result reached almost 90% by the end of 1 year especially so in the fibrous strictures. Four out of the eight live patients (50%) had cough for 2 months and two (25%) had mild blood-tinged sputum treated by inhalation and mucolytic agents. Secondary intervention was required in one patient at 1 month because of recurrent symptoms. The patient with tracheo-oesophageal fistula required surgical intervention because of fracture of the stent. Fluoroscopically guided balloon dilatation and stenting of the tracheal stenosis is an effective non-surgical therapy resulting in cure of fibrous strictures and palliation in cases of malignancy.
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    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.
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    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.
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    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.
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    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.
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    Role of diffusion tensor imaging in differentiating subtypes of meningiomas
    (JOURNAL OF NEURORADIOLOGY, 2010)
    Purpose. - Meningiomas are the most common extraaxial intracranial type of tumor, and their management and prognosis depend on their grade and histology. Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) are two new imaging techniques that have proved helpful in elucidating the microarchitecture of brain tumors. The aim of the present study was to assess the role of diffusion and diffusion tensor metrics in the identification and classification of meningioma grades and subtypes.Methods and materials. - A total of 21 consecutive patients with meningioma were included in this retrospective study, of whom 16 had benign meningiomas (three fibroblastic, 11 transitional/mixed, two meningothelial) and five had atypical meningiomas. Tumor mean diffusivity (Day), fractional anisotropy (FA), linear anisotropy (CL), planar anisotropy (CP), spherical anisotropy (CS) and eigenvalues (e1, e2, e3) were measured in all cases, and differences in diffusion tensor metrics between atypical, fibroblastic and other benign (transitional, meningothelial) meningiomas were statistically analyzed using the Mann Whitney test.Results. - No statistically significant differences were found among the mean Day values for atypical, fibroblastic and other benign meningiomas. Both atypical and fibroblastic meningiomas showed significantly higher mean FA values and lower mean CS values compared with other meningiomas (P<0.01), but no statistically significant difference in these values between each other. Atypical meningiomas showed higher CL values compared with fibroblastic and other benign meningiomas but, again, the difference was not statistically significant. Both atypical and fibroblastic meningiomas showed statistically significantly higher CP values and lower e3 values compared with transitional meningiomas (P<0.01).Conclusion. - These results suggest that diffusion tensor metrics may be helpful in the differentiation of atypical, fibroblastic and other benign meningiomas. (C) 2010 Elsevier Masson SAS. All rights reserved.
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    Susceptibility weighted imaging: a new tool in magnetic resonance imaging of stroke
    (CLINICAL RADIOLOGY, 2009)
    Susceptibility weighted imaging (SWI) is a magnetic resonance (MR) technique that is exquisitely sensitive to paramagnetic substances, such as deoxygenated blood, blood products, iron, and calcium. This sequence allows detection of haemorrhage as early as 6 h and can reliably detect acute intracerebral parenchymal, as well as subarachnoid haemorrhage. It detects early haemorrhagic transformation within an infarct and provides insight into the cerebral haemodynamics following stroke. It helps in the diagnosis of cerebral venous thrombosis. It also has applications in the work-up of stroke patients. The sequence helps in detecting microbleeds in various conditions, such as vasculitis, cerebral autosomal dominant arteriopathy, subacute infarcts and leucoencephalopathy (CADASIL), amyloid angiopathy, and Binswanger's disease. The sequence also aids in the diagnosis of vascular malformations and perinatal cerebrovascular injuries. This review briefly illustrates the utility of this MR technique in various aspects of stroke diagnosis and management. (C) 2008 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
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    Uncommon presentation of intracranial cryptococcal infection mimicking tuberculous infection in two immunocompetent patients
    (SINGAPORE MEDICAL JOURNAL, 2009)
    Cryptococcal infection of the brain is commonly seen in immunocompromised patients but rarely considered as the differential diagnosis in immunocompetent patients. We present two cases of cryptococcosis involving the brain in immunocompetent patients, which strongly mimicked tuberculous infection in both conventional as well as advanced magnetic resonance (MR) imaging, and the disease was only confirmed after histopathological/cerebrospinal fluid serological study. One patient was a 52-year-old woman, and the second patient was a 23-year-old man. These two cases highlight the need for workup of fungal infections in immunocompetent patients from the tuberculous endemic regions, even when the imaging is highly suspicious of tuberculous lesions. The imaging findings in advanced MR imaging techniques such as diffusion, perfusion, susceptibility-weighted imaging and MR spectroscopy are discussed.
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    Usefulness of T2*-weighted MR sequence for the diagnosis of subfrontal schwannoma
    (JOURNAL OF NEURORADIOLOGY, 2007)
    Subfrontal schwannomas are rare tumors that are usually diagnosed during surgery. They are often misdiagnosed as meningioma or esthesioneuroblastoma because of their similar clinical and radiological features. We report a case of schwannoma arising from the floor of the anterior cranial fossa that had radiological features similar to that of meningioma. However, T2*-weighted MR imaging revealed multiple foci of Low signal intensities within the tumor related to microbleeds, which suggested a diagnosis of schwannoma that was confirmed by histopathology. This case report demonstrates the usefulness of T2*-weighted sequence in distinguishing meningioma from schwannoma, especially in cases where the tumor has an unusual location. (C) 2007 Elsevier Masson SAS. All rights reserved.