Papers by Chandrasekharan Kesavadas
The Lancet Neurology, 2008
Background Cysticercosis due to Taenia solium is a cause of adult-acquired seizures and epilepsy ... more Background Cysticercosis due to Taenia solium is a cause of adult-acquired seizures and epilepsy even in patients with only calcifi ed larval cysts. Transient perilesional brain oedema is seen around the calcifi ed foci but its importance, association with seizures, incidence, and pathophysiology are unknown.
Journal of Alzheimer's disease : JAD, Jan 12, 2016
The contribution of cerebral small vessel disease to cognitive decline, especially in non-Caucasi... more The contribution of cerebral small vessel disease to cognitive decline, especially in non-Caucasian populations, is not well established. We examined the relationship between cerebral small vessel disease and motoric cognitive risk syndrome (MCR), a recently described pre-dementia syndrome, in Indian seniors. 139 participants (mean age 66.6 ± 5.4 y, 33.1% female) participating in the Kerala-Einstein study in Southern India were examined in a cross-sectional study. The presence of cerebral small vessel disease (lacunar infarcts and cerebral microbleeds (CMB)) and white matter hyperintensities on MRI was ascertained by raters blinded to clinical information. MCR was defined by the presence of cognitive complaints and slow gait in older adults without dementia or mobility disability. Thirty-eight (27.3% ) participants met MCR criteria. The overall prevalence of lacunar infarcts and CMB was 49.6% and 9.4% , respectively. Lacunar infarcts in the frontal lobe, but no other brain regions, ...
Neurology, 2009
A 24-year-old woman presented with 2 months of episodic vertigo, vomiting, and headache triggered... more A 24-year-old woman presented with 2 months of episodic vertigo, vomiting, and headache triggered by abrupt head movements, lasting from a few minutes to 1 hour. She was asymptomatic between the attacks and had mild gait ataxia on examination. Brain MRI revealed obstructive hydrocephalus and a cystic lesion in the fourth ventricle (figures 1 and 2). Her symptoms subsided after cyst excision; a histopathologic diagnosis of neurocysticercosis was made. This clinical picture matches the Bruns syndrome, due to a mobile ventricular mass producing episodic hydrocephalus on changing head posture. 1,2 Cysticercosis of the fourth ventricle can be fatal and mandates prompt neurosurgical treatment.
The neuroradiology journal, Jan 13, 2015
* Equal Contribution.Neuroeconomics employs neuroscience techniques to explain decision-making be... more * Equal Contribution.Neuroeconomics employs neuroscience techniques to explain decision-making behaviours. Prospect theory, a prominent model of decision-making, features a value function with parameters for risk and loss aversion. Recent work with normal participants identified activation related to loss aversion in brain regions including the amygdala, ventral striatum, and ventromedial prefrontal cortex. However, the brain network for loss aversion in pathologies such as depression has yet to be identified. The aim of the current study is to employ the value function from prospect theory to examine behavioural and neural manifestations of loss aversion in depressed and healthy individuals to identify the neurobiological markers of loss aversion in economic behaviour. We acquired behavioural data and fMRI scans while healthy controls and patients with depression performed an economic decision-making task. Behavioural loss aversion was higher in patients with depression than in healthy controls. fMRI results revealed that the two groups shared a brain network for value function including right ventral striatum, ventromedial prefrontal cortex, and right amygdala. However, the neural loss aversion results revealed greater activations in the right dorsal striatum and the right anterior insula for controls compared with patients with depression, and higher activations in the midbrain region ventral tegmental area for patients with depression compared with controls. These results suggest that while the brain network for loss aversion is shared between depressed and healthy individuals, some differences exist with respect to differential activation of additional areas. Our findings are relevant to identifying neurobiological markers for altered decision-making in the depressed.
Neurology India
To evaluate the efficacy of diffusion fiber tractography (DFT) and voxel-based morphometry (VBM) ... more To evaluate the efficacy of diffusion fiber tractography (DFT) and voxel-based morphometry (VBM) for lateralizing language in comparison with functional magnetic resonance imaging (fMRI) to noninvasively assess hemispheric language lateralization in normal healthy volunteers. The aim of the present study is to evaluate the concordance of language lateralization obtained by diffusion tensor imaging (DTI) and VBM to fMRI, and thus to see whether there exists an anatomical correlate for language lateralization result obtained using fMRI. This is an advanced neuroimaging study conducted in normal healthy volunteers. Fifty-seven normal healthy subjects (39 males and 18 females; age range: 15-40 years) underwent language fMRI and 30 underwent direction DTI. fMRI language laterality index (LI), fiber tract asymmetry index (AI), and tract-based statistics of dorsal and ventral language pathways were calculated. The combined results were correlated with VBM-based volumetry of Heschl's gy...
Purpose: The selection of ideal candidates for extratemporal resective epilepsy surgery is a chal... more 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.
To assess the prevalence and attributes of atypical language lateralization (ALL) in patients wit... more 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). 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. 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 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;6 years, atypical IPI, nonunilateral temporal IEDs, and extratemporal MRI abnormalities independently predicted ALL. The likelihood of ALL was very low ( approximately 1%) when all of these four risk factors were absent, whereas it was very high (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;95%), if any three or all four of them were present. 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.
Introduction Increased concentrations of deoxyhemoglobin within veins can induce susceptibility c... more Introduction Increased concentrations of deoxyhemoglobin within veins can induce susceptibility changes resulting in increased conspicuity in susceptibility weighted imaging (SWI). Compensatory mechanisms following reduced cerebral perfusion due to carotid occlusive disease may not be sufficient to meet demands of ischemic tissue and increased tissue oxygen extraction ratio results in relative increase in deoxyhemoglobin levels in the venous blood draining affected hemisphere. We assessed whether patients with carotid disease display prominence of veins over affected cerebral hemisphere. Methods Eighteen patients with unilateral carotid occlusion or critical carotid stenosis proven by magnetic resonance angiography (MRA) were selected. The medical records and MRI findings including SWI and MRA were reviewed. The SWI images were studied for the presence of asymmetry of veins over the cerebral hemispheres and were correlated with the site and severity of stenosis or occlusion. The veins were assumed to be conspicuous and asymmetric if there were more numerous veins and/or large veins with greater signal loss observed compared with opposite normal hemisphere. Results In about half of patients, prominence of veins was noted in the cerebral hemisphere ipsilateral to side of occlusion. This was not observed in patients with significant extracranial carotid stenosis. The SWI abnormalities were seen extending beyond the boundaries of occluded vascular territory. There was good agreement between two observers in all the patients who showed positive finding. Also there was no interobserver variation in patients with negative findings. Conclusion The increased susceptibility arising out of increased deoxyhemoglobin to oxyhemoglobin ratio leads to visualization of prominent veins over the affected cerebral hemisphere on SWI.
Objective-To determine whether the major temporal lobe white matter tracts in patients with tempo... more Objective-To determine whether the major temporal lobe white matter tracts in patients with temporal lobe epilepsy manifest abnormal water diffusion properties.
Functional magnetic resonance imaging (fMRI) has revolutionized our understanding of functional n... more Functional magnetic resonance imaging (fMRI) has revolutionized our understanding of functional networks and cerebral organization in both normal and pathological brains. In the present review, we describe the use of fMRI for mapping language in epilepsy patients prior to surgical intervention including a discussion of methodological issues and task design, comparisons between fMRI and the intracarotid sodium amobarbital test, fMRI studies of language reorganization, and the use of fMRI laterality indexes to predict outcome after anterior temporal lobectomy.
Neuroenteric cysts are developmental cysts that should be differentiated from other, more common ... more Neuroenteric cysts are developmental cysts that should be differentiated from other, more common non-neoplastic cysts as well as cystic neoplasms. While these lesions may have varied imaging findings, T1 hyperintense prepontine lesion due to mucinous/proteinaceous content is characteristic. Location and imaging characteristics aid in formulating the correct diagnosis of neuroepithelial/neuroenteric cysts. Magnetic resonance spectroscopy (MRS) has the specific finding of N-Acetyl Aspartate (NAA)-like peak at 2.02 ppm which is not seen in other cystic lesions. In this study, we aim to discuss the imaging findings of these lesions on conventional and advanced MRI findings and provide radiologic-pathologic correlation. We also briefly describe the pathogenesis, embryology and radiological differential diagnoses of these cysts.
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Papers by Chandrasekharan Kesavadas