Browsing by Author "Thomas, Bejoy"

Now showing 1 - 20 of 42
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    A 6-year-old girl with progressive ataxia
    (JOURNAL OF CLINICAL NEUROSCIENCE, 2012)
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    Aberrant petrous internal carotid artery with cochlear anomaly-an unusual association
    (SURGICAL AND RADIOLOGIC ANATOMY, 2008)
    The magnetic resonance imaging (MRI) in a female patient who presented with headache and hearing loss revealed aberrant course of the petrous segment of internal carotid artery (ICA). Computed tomography (CT) of the temporal bone done to confirm the findings of MRI revealed aberrant course of right ICA, a persistent stapedial artery (PSA) and absent foramen spinosum on the same side. In addition patient had a cystic cochleovestibular anomaly on the right side with both conditions may probably be contributing to her hearing loss.
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    Applications of 3D CISS sequence for problem solving in neuroimaging.
    (The Indian journal of radiology & imaging, 2011)
    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.
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    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.
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    Calcified neurocysticercosis lesions and hippocampal sclerosis: Potential dual pathology?
    (EPILEPSIA, 2012)
    In areas where cysticercosis is endemic, calcified neurocysticercosis lesion(s) (CNL) and hippocampal sclerosis (HS) commonly coexist in patients with localization-related epilepsies. To understand the pathogenesis of HS associated with CNL, we compared the characteristics of three groups of patients with antiepileptic drugresistant epilepsies: CNL with HS, CNL without HS (CNL alone), and HS without CNL (HS alone). In comparison to patients with CNL alone, those with CNL with HS had CNL more frequently located in the ipsilateral temporal lobe. Those with CNL with HS had a lower incidence of febrile seizures, older age at initial precipitating injury and at onset of habitual complex partial seizures, and more frequent clustering of seizures and extratemporal/bitemporal interictal epileptiform discharges as compared to patients with HS alone. Our study illustrates that HS associated with CNL might have a different pathophysiologic basis as compared to classical HS.
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    Can diffusion tensor metrics help in preoperative grading of diffusely infiltrating astrocytomas? A retrospective study of 36 cases
    (NEURORADIOLOGY, 2011)
    Diffusion weighted imaging and diffusion tensor imaging (DTI) give information about the amount and directionality of water diffusion occurring in a given tissue. Here we study the role of diffusion tensor metrics including fractional anisotropy (FA) and spherical anisotropy (CS) in preoperative grading of diffusely infiltrating astrocytomas.We performed DTI in 38 patients with pathologically proven diffusely infiltrating astrocytomas, who were classified into two groups, i.e., 15 patients with high-grade astrocytoma (HGAs, WHO grade III and IV) and 23 patients with low-grade astrocytoma (LGAs, WHO grade II). We measured maximum FA and minimum CS values in all cases from tumor. Histopathological diagnosis was established in all cases.The mean maximum FA values were higher in HGA (0.583 +/- 0.104) than LGA (0.295 +/- 0.058), while mean minimum CS values were lower in HGA (0.42 +/- 0.121) than LGA (0.722 +/- 0.061). The difference in the diffusion tensor indices between HGA and LGA was found to be statistically significant with P value of < 0.001. Keeping cutoff FA value of 0.4, all HGAs showed higher maximum FA values, and all LGAs showed lower maximum FA values. Also, all HGAs showed minimum CS values less than a cutoff value of 0.6, and all LGAs showed minimum CS values higher than 0.6.Diffusion tensor metrics such as maximum FA and minimum CS can help to differentiate HGA from LGA.
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    Clinical applications of functional MRI in epilepsy.
    (The Indian journal of radiology & imaging, 2008)
    The role of functional MRI (fMRI) in the presurgical evaluation of patients with intractable epilepsy is being increasingly recognized. Real-time fMRI is an easily performable diagnostic technique in the clinical setting. It has become a noninvasive alternative to intraoperative cortical stimulation and the Wada test for eloquent cortex mapping and language lateralization, respectively. Its role in predicting postsurgical memory outcome and in localizing the ictal activity is being recognized. This review article describes the biophysical basis of blood-oxygen-level-dependent (BOLD) fMRI and the methodology adopted, including the design, paradigms, the fMRI setup, and data analysis. Illustrative cases have been discussed, wherein the fMRI results influenced the seizure team's decisions with regard to diagnosis and therapy. Finally, the special issues involved in fMRI of epilepsy patients and the various challenges of clinical fMRI are detailed.
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    Clinical applications of susceptibility weighted MR imaging of the brain - a pictorial review
    (NEURORADIOLOGY, 2008)
    Introduction Susceptibility-weighted imaging (SWI) is a novel magnetic resonance (MR) technique that exploits the magnetic susceptibility differences of various tissues, such as blood, iron and calcification. This pictorial review covers many clinical conditions illustrating its usefulness.Methods SWI consists of using both magnitude and phase images from a high-resolution, three-dimensional fully velocity-compensated gradient echo sequence. Phase mask is created from the MR phase images, and multiplying these with the magnitude images increase the conspicuity of the smaller veins and other sources of susceptibility effects, which is depicted using minimal intensity projection (minIP).Results The phase images are useful in differentiating between diamagnetic and paramagnetic susceptibility effects of calcium and blood, respectively. This unique MR sequence will help in detecting occult low flow vascular lesions, calcification and cerebral microbleed in various pathologic conditions and aids in characterizing tumors and degenerative diseases of the brain. This sequence also can be used to visualize normal brain structures with conspicuity.Conclusion Susceptibility-weighted imaging is useful in differentiating and characterizing diverse brain pathologies.
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    Clinical utility of susceptibility-weighted imaging in vascular diseases of the brain
    (NEUROLOGY INDIA, 2010)
    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.
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    Concepts and Controversies in Nonketotic Hyperglycemia-Induced Hemichorea: Further Evidence from Susceptibility-Weighted MR Imaging
    (JOURNAL OF MAGNETIC RESONANCE IMAGING, 2009)
    Hyperglycemia-induced hemichorea can show T1 hyperintensity of the contralateral striatum on MRI. This is thought to be due to petechial hemorrhages or gemistocytic astrocyte accumulation. This study explores the utility of susceptibility-weighted imaging (SWI) and diffusion-weighted imaging (DWI) in identifying the nature of these lesions. Three patients underwent MR imaging of the brain with SE T1, F SE T2. DWI, and SWI. T1 images showed hyperintensity predominantly involving the contralateral striatum, where mild (two cases) to moderate (one case) restricted diffusion (low apparent diffusion coefficient [ADC]) was detected on DWI. SWI demonstrated bilateral symmetrical hypointensities in the first two cases, suggesting age associated mineralization. In addition, increased susceptibility change (hypointensity) was also noted in the right putamen in the first and the third cases, suggesting paramagnetic mineral deposition. T1 hyperintensity may be from the protein hydration layer inside the cytoplasm of swollen gemistocytes appearing after an acute cerebral injury. These astrocytes also express metallothionein with zinc, which is thought to be the cause of asymmetric hypointensity of the posterior putamen on SWI. ADC values were thought to be useful for prognostication: however, they should be interpreted cautiously in the presence of susceptibility changes.
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    Diffusion Tensor and Tensor Metrics Imaging in Intracranial Epidermoid Cysts
    (JOURNAL OF MAGNETIC RESONANCE IMAGING, 2009)
    Purpose: To explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) In characterizing the structural pathology of epidermoid cysts. DTI gives Information about the tissue structure: a high fractional anisotropy (FA) indicates a highly structured orientation of the tissue, fibers, or white matter tracts. Based on the tensor rank, a set of three metrics has been described that can be used to measure the directional dependence of diffusion: linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS). DTM takes into account the shape of diffusion anisotropy and hence may provide better insight Into the orientation of structures than FA.Materials and Methods: DTI was performed in three patients with epidermoid cysts. FA, directionally-averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), and DTM, such as CL, CP, and CS, were measured from the tumor core as well as from the normal-appearing white matter. Histopathological correlation was obtained.Results: Epidermoid cysts showed high FA with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were. high, but not. as high as that for the white matter, CP values were higher and CL values were lower than those obtained for the white matter in various regions.Conclusion: High CP values suggest preferential diffusion of water molecules along a two-dimensional geometry, which could be attributed to the well-structured orientation of keratin filaments and flakes within the tumor as demonstrated by histopathology. Advanced imaging modalities like DTI with DTM can provide Information regarding the microstructural anatomy of the epidermoid cysts.
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    Endovascular treatment of direct carotid cavernous fistulae: a pictorial review
    (NEURORADIOLOGY, 2006)
    Introduction Direct carotid-cavernous fistulae (CCFs) are type A fistulae according to Barrow's classification. Endovascular treatment of these lesions is challenging.Methods The purpose of this review was to evaluate the endovascular treatment of direct CCFs. We also describe the technique, symptomatology and complications associated with the procedure and report on the long-term follow-up in our treated patients.Results A total of 89 patients with a direct CCF were treated. All patients had baseline brain CT or MR imaging. Treatment comprised transarterial balloon or coil embolizations. The patients were followed up at 1 month and then every 6 months thereafter. Detachable balloons were used in 79 fistulae. In 12 fistulae the balloon could not be negotiated through the fistula and these fistulae were treated with transarterial coil occlusion. Clinical outcomes of the treated patients evaluated at 1 month were: 79 patients (88.8%) cured, 9 (10.1%) significantly improved, 1 (1.1%) remaining static.Conclusion Endovascular treatment of direct CCFs is safe and effective and results in long-term cure.
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    Focal Cortical Dysplasia (FCD) lesion analysis with complex diffusion approach
    (COMPUTERIZED MEDICAL IMAGING AND GRAPHICS, 2009)
    Identification of Focal Cortical Dysplasia (FCD) can be difficult due to the subtle MRI changes. Though sequences like FLAIR (fluid attenuated inversion recovery) can detect a large majority of these lesions, there are smaller lesions without signal changes that can easily go unnoticed by the naked eye. The aim of this study is to improve the visibility of focal cortical dysplasia lesions in the T1 weighted brain MRI images. In the proposed method, we used a complex diffusion based approach for calculating the FCD affected areas. Based on the diffused image and thickness map, a complex map is created. From this complex map; FCD areas can be easily identified. MRI brains of 48 subjects selected by neuroradiologists were given to computer scientists who developed the complex map for identifying the cortical dysplasia. The scientists were blinded to the MRI interpretation result of the neuroradiologist. The FCD could be identified in all the patients in whom surgery was done, however three patients had false positive lesions. More lesions were identified in patients in whom surgery was not performed and lesions were seen in few of the controls. These were considered as false positive. This computer aided detection technique using complex diffusion approach can help detect focal cortical dysplasia in patients with epilepsy. (C) 2009 Elsevier Ltd. All rights reserved.
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    Functional magnetic resonance imaging of the brain: a quick review.
    (Neurology India, 2010)
    Ability to non-invasively map the hemodynamic changes occurring focally in areas of brain involved in various motor, sensory and cognitive functions by functional magnetic resonance imaging (fMRI) has revolutionized research in neuroscience in the last two decades. This technique has already gained clinical use especially in pre-surgical evaluation of epilepsy and neurosurgical planning of resection of mass lesions adjacent to eloquent cortex. In this review we attempt to illustrate basic principles and techniques of fMRI, its applications, practical points to consider while performing and evaluating clinical fMRI and its limitations.
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    Hypertrophic pachymeningitis in a patient with Takayasu arteritis: One more association
    (ANNALS OF INDIAN ACADEMY OF NEUROLOGY, 2012)
    Hypertrophic pachymeningitis (HP) is a rare chronic inflammatory disease of the dura mater, described in association with various infections, systemic vasculitides such as Wegeners granulomatosis and giant cell arteritis. However, HP in association with Takayasu arteritis (TA) has not been described. We report a young woman who presented with headache, seizures, and right third and fourth cranial neuropathy. Magnetic resonance imaging of the brain showed HP in bifrontal and right temporal region extending to cavernous sinus. She was also found to have systemic hypertension, stenosis of left subclavian, and left renal artery with narrowing of abdominal aorta, satisfying the diagnostic criteria for TA. A detailed evaluation for secondary causes of HP failed to reveal an alternative etiology. This report describes an unusual association of HP in a patient with TA, also emphasizing that seizures and cranial neuropathy may further expand the spectrum of neurological manifestations in patients with TA.
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    Insights from a rare clinical presentation of herpes simplex encephalitis: adding to the catatonic dilemma?
    (The neurologist, 2011)
    BACKGROUND: Catatonia is associated with a variety of psychiatric and medical illnesses. Very little research is available on the syndrome and the exact neurobiological correlates are not known. Though various cortical and subcortical circuits are implicated in the pathogenesis, the role of cerebellum is unknown. We report an unusual presentation of herpes simplex encephalitis, clinically as catatonic stupor and radiologically as isolated symmetrical cerebellar involvement affecting the posterior cerebellum. We discuss the possible role of the cerebellum in producing a catatonic state.CASE REPORT: We describe the clinical presentation of catatonia in a 19-year-old woman with herpes simplex encephalitis. Her magnetic reasonance imaging showed features of viral cerebellitis involving the posterior cerebellum with hemorrhagic transformation. She lacked the classical frontotemporal involvement of herpes and recovered completely without physical or neuropsychological sequelae. She did not show signs associated with cerebellar disease at any point during the illness.CONCLUSIONS: This case provides compelling evidence for the possible role of the posterior cerebellum in the clinical presentation of catatonia. This is probably related to its role in controlling the nonmotor cerebral functions through corticocerebellar connections. Further studies of catatonic syndromes are needed to establish this association.
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    Iophendylate myelography induced thoracic arachnoiditis, arachnoid cyst and syrinx, four decades later
    (BRITISH JOURNAL OF NEUROSURGERY, 2010)
    Iophendylate (Myodil) was a popular oil-based contrast agent used until late 1980s for myelography, ventriculography and cisternography. Although several long-term sequelae have been reported in literature, they are extremely rare. We report a rare occurrence of symptomatic dorsal arachnoid cyst 40 years after Myodil myelography.
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    Ischemic hyperintensities on T1-weighted magnetic resonance imaging of patients with stroke: New insights from susceptibility weighted imaging
    (NEUROLOGY INDIA, 2010)
    Hyperintensities on T1-weighted magnetic resonance imaging (MRI) in the setting of brain ischemia are usually considered hemorrhagic transformations. Such changes can also be seen due to "incomplete infarction" with selective neuronal loss. Arguments regarding the cause of these T1 hyperintensities have shuttled between gemistocytic astrocyte accumulation, tissue calcification and paramagnetic substance deposition. Susceptibility weighted imaging (SWI), a sensitive modality for detecting paramagnetic agents and blood products, has never been used to resolve this issue. The study was aimed to evaluate the SWI signal changes of T1 hyperintense lesion in stroke patients and understand its usefulness in differentiating a hemorrhagic infarct and an incomplete infarct. All the seven patients with infarct, having hyperintensities on T1 weighted MRI seen over the last one year were subjected to SWI. In none of the patients SWI failed to show any blooming. By doing SWI for T1-weighted hyperintensities, we can differentiate hemorrhagic infarct and a non-hemorrhagic "incomplete infarct". This differentiation will immensely help in planning management strategy and prognostication.