Browsing by Author "Kesavadas, Chandrasekharan"

Now showing 1 - 20 of 44
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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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    Acute subdural effusion in vasculitis
    (NEUROLOGY INDIA, 2008)
    We report a 29-year-old man with a unique presentation of vasculitis as acute unilateral subdural effusion and meningoencephalitis. Magnetic resonance imaging showed a brainstem lesion that spread to the thalamus over time. There were no systemic features of vasculitis other than a positive pathergy test. Histopathological examination I from the pathergy site showed neutrophilic infiltrate and leucocytoclastic vasculitis. The condition was steroid responsive and he remained in remission at two years' follow-up. The anatomy of the brainstem lesion, absence of other inflammatory and infective conditions on evaluation suggests a vasculitic pathology either as primary central nervous system angiitis or as neurological presentation of systemic vasculitis like Behcet's disease although the international diagnostic criteria for Behcet's were not fulfilled.
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    An audit of the presurgical evaluation and patient selection for extratemporal resective epilepsy surgery in a resource-poor country
    (SEIZURE-EUROPEAN JOURNAL OF EPILEPSY, 2012)
    Purpose: The selection of ideal candidates for extratemporal resective epilepsy surgery is a challenge in resource-poor countries because of the limited presurgical diagnostic facilities and their affordability. To audit the presurgical evaluation strategy and selection for extratemporal resective epilepsy surgery in a resource-poor region.Methods: From the prospective database maintained at an epilepsy surgery center in southern India, we reviewed the data of consecutive patients who underwent presurgical evaluation from January 2005 through December 2008 for antiepileptic drug-resistant focal epilepsies emanating from the frontal, parietal and occipital lobes. Out of 285 patients, only 71 (24.9%) underwent resective surgery; the remaining 214 (75.1%) patients could not be selected for surgery. We inquired the reasons for their exclusion from surgery.Results: The difference in the rates of seizure-free outcome between surgical and non-surgical groups was highly significant (73.2% vs. 7.7%, P < 0.0005). The major reasons for exclusion from surgery were normal MRI in 107 (50%), inability to afford invasive EEG monitoring in 40 (18.7%) and lesion location adjacent to eloquent cortical areas in 27 (12.6%) patients. While clustering of seizures and presence of preoperative neurological deficits favored surgical selection, the presence of secondary generalized seizures and discordant interictal epileptiform abnormalities were associated with exclusion from surgery.Conclusions: We conclude that, in a resource-poor country, ideal candidates for extratemporal resective epilepsy surgery are those with well-circumscribed lesions not adjoining eloquent cortical areas. In such patients, concordant EEG findings and absence of preoperative secondary generalized seizures reinforce selection for surgery. (C) 2012 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.
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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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    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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    Changing signal intensity of a craniopharyngioma
    (NEUROLOGY INDIA, 2010)
    Craniopharyngiomas can present as suprasellar cystic lesion with varied imaging appearance. In magnetic resonance imaging using T1-weighted sequence, the cyst can show hypointense, isointense or hyper intense signals depending on the cyst content. We report a case where the T1 signal intensity of a craniopharyngioma changed over time. The hypointense lesion had become hyper intense in the follow-up scan after six months. Such change in signal intensity is described with Rathke's cleft cyst but has not been reported with craniopharyngioma. The possible reason for this change in signal intensity is discussed.
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    Clinical and functional outcome and factors predicting prognosis in osmotic demyelination syndrome (central pontine and/or extrapontine myelinolysis) in 25 patients
    (JOURNAL OF NEUROLOGY NEUROSURGERY AND PSYCHIATRY, 2011)
    Aims To assess the functional and clinical outcome in a sizeable cohort of patients with osmotic demyelination syndrome (ODS) and to characterise the factors which could predict the final outcome.Methods Twenty five consecutive patients with ODS formed the study cohort. The diagnosis of ODS was based on clinical features with corroborating imaging findings. Two functional scales-Functional Independent Measure (FIM) and Disability Rating Scale (DRS)-were applied to assess the functional status at the time of admission, discharge and last follow-up. Patients who became independent for activities of daily living (ADL) at last follow-up were classified as favourable outcome, and those who died or became dependent for ADL were classified as a poor outcome group respectively. The Fisher exact test and Manne-Whitney U test were used to assess categorical and continuous variables respectively.Results The mean age at diagnosis was 53 +/- 14 years. Five (20%) had central pontine myelinolysis, seven (28%) had extrapontine myelinolysis, and 13 (52%) had both. Hyponatraemia and hypokalaemia were noted in 20 (80%) and 10 (40%) patients respectively. Six (24%) received intravenous methylprednisolone. Eleven (46%) had a favourable outcome at a mean follow- up of 2.262.5 years. Hyponatraemia <= 115 mEq (p=0.04), associated hypokalaemia (p 0.04) and low Glasgow Coma Scale (GCS) (p=0.008) at presentation were predictive of poor outcome. The mean FIM score at admission (p=0.05) and at discharge (p=0.01), and mean DRS at admission (p=0.05) were predictive of poor outcome.Conclusions Higher GCS scores, better scores in functional scales in hospital, less severe hyponatraemia and absence of superadded hypokalaemia predicted favourable outcome.
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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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    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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    Corpora amylacea in mesial temporal lobe epilepsy: Clinico-pathological correlations
    (EPILEPSY RESEARCH, 2007)
    Purpose: To investigate the etectro-clinical significance of premature accumulation of corpora amylacea (CoA) in the resected hippocampus of patients with medically refractory mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS).Methods: We compared the clinical and EEG characteristics, and post-operative seizure outcome of 373 (mean age 29.4 years, range 7-55 years) surgically treated MTLE-HS patients with (MTLE-HS-CoA(+), n = 129 [34.5%]) and without. (MTLE-HS-CoA(-), n = 244 [65.5%]) CoA.Results: Age at surgery was significantly higher and duration of epilepsy before surgery was significantly longer for MTLE-HS-CoA(+) patients compared to MTLE-HS-CoA(-) patients. Although the distribution of interictal epileptiform EEG abnormalities did not differ, type 1 ictal EEG pattern was more frequent in MTLE-HS-CoA(+) patients. Among the 21 patients with major interictal psychosis detected prior to epilepsy surgery, 19 (90.5%) belonged to MTLE-HS-CoA(+) group. Schizophrenia-like psychosis was most. prevalent. The post-operative seizure-free outcome was comparable, but significantly more MTLE-HS-CoA(-) patients were free of antiepileptic drugs.Conclusions: Overall, our observations support the hypothesis that the pathological process in MTLE-HS is progressive. MTLE-HS-CoA(+) patients are predisposed to increased psychiatric morbidity. In vivo detection of hippocampal CoA accumulation in the future will help us to understand the neurobiological significance of this phenomenon. (C) 2007 Elsevier B.V. All rights reserved.
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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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    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.
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    Evolution and long term outcome in patients presenting with large demyelinating lesions as their first clinical event
    (JOURNAL OF THE NEUROLOGICAL SCIENCES, 2010)
    Objectives: To describe the long term evolution and outcome of a homogeneous cohort of patients (n = 14) with large demyelinating lesions (LDLs) as the first clinical event from a group of idiopathic inflammatory demyelinating diseases of central nervous system.Methods: Detailed review of LDLs from December 2002-January 2007 was made. Patients had at least two magnetic resonance imaging (MRI) and minimum follow-up of 2 years. The disability was assessed using Estimated Expanded Disability Status Scale (EDSS) and Rappaport Disability Rating Scale (DRS) at onset and last follow-up.Results: Fourteen consecutive LDL patients (male = 7), with mean age 32.7 years and mean follow-up of 45.5 months were included. Motor deficits (79%) and cognitive symptoms (43%) marked the onset, none had optic neuritis. All except two responded to steroids. Follow-up MRI showed complete resolution in 43%, 57% showing marked reduction in size. On follow-up, 2 relapsed. Mean EDSS and DRS at presentation were 5.93 and 9.07 and at last follow-up were 1.75 and 2.25 (p<0.001).Conclusions: Our data suggests that, patients presenting with LDLs as their first clinical event behaves distinctly in their presentation, imaging characteristics, prognosis and long term outcome as compared to MS and ADEM. Albeit significant disability at the onset, these patients show an excellent response to treatment with good functional recovery in long term and rare relapses. (C) 2010 Elsevier B.V. All rights reserved.
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    Extent of initial injury determines language lateralization in mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS)
    (EPILEPSIA, 2009)
    P>Purpose:To assess the prevalence and attributes of atypical language lateralization (ALL) in patients with left mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS).Methods:We recruited consecutive patients with left MTLE-HS, who had undergone resective surgery and had pathologically proven HS. Based on the Wada test, language lateralization was classified into typical (left hemispheric) or atypical (right hemispheric or codominant). We assessed the attributes of patients with ALL using univariate and multivariate analyses.Results:Of 124 patients with left MTLE-HS, 23 (18.5%) had ALL. ALL occurred more frequently in patients with severe initial precipitating injury (IPI), early onset of epilepsy, and a short latent period between IPI and onset of habitual seizures. ALL was more common in patients with bitemporal and extratemporal interictal epileptiform discharges (IEDs) on electroencephalogram (EEG) and extratemporal changes on magnetic resonance imaging (MRI). On multivariate analyses, the age at onset of habitual seizures < 6 years, atypical IPI, nonunilateral temporal IEDs, and extratemporal MRI abnormalities independently predicted ALL. The likelihood of ALL was very low (similar to 1%) when all of these four risk factors were absent, whereas it was very high (> 95%), if any three or all four of them were present.Conclusions:ALL occurs in one-fifth of patients with left MTLE-HS. ALL is more frequent in those with structural or functional extrahippocampal involvement and early onset of epilepsy interrupting the development of normal language networks. Because ALL is uncommon in those with damage/dysfunction restricted to the hippocampus, the hippocampus itself may have only a limited role in determining language lateralization.
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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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    Hereditary spastic paraplegia with a thin corpus callosum
    (PEDIATRIC RADIOLOGY, 2007)
    We report a 15-year-old boy with autosomal recessive complicated hereditary spastic paraplegia with a thin corpus callosum (HSP-TCC). The involvement of the corpus callosum was characteristic with the genu and body predominantly affected with relative sparing of the splenium. HSP-TCC is being increasingly recognized over a wider geographical area than earlier believed. We now report a case of HSP-TCC from the Indian subcontinent.