Ashalatha Radhakrishnan - Academia.edu (original) (raw)

Papers by Ashalatha Radhakrishnan

DOAJ (DOAJ: Directory of Open Access Journals), 2010

Epileptic Disorders, May 31, 2023

Transfusion and Apheresis Science, Jun 1, 2023

Neurology India, Nov 1, 2020

Neuroradiology, Apr 25, 2019

Purpose Our aim is to investigate whether rs-fMRI can be used as an effective technique to study ... more Purpose Our aim is to investigate whether rs-fMRI can be used as an effective technique to study language lateralization. We aim to find out the most appropriate language network among different networks identified using ICA. Methods Fifteen healthy right-handed subjects, sixteen left, and sixteen right temporal lobe epilepsy patients prospectively underwent MR scanning in 3T MRI (GE Discovery™ MR750w), using optimized imaging protocol. We obtained task-fMRI data using a visual-verb generation paradigm. Rs-fMRI and language-fMRI analysis were conducted using FSL software. Independent component analysis (ICA) was used to estimate rs-fMRI networks. Dice coefficient was calculated to examine the similarity in activated voxels of a common language template and the rs-fMRI language networks. Laterality index (LI) was calculated from the task-based language activation and rs-fMRI language network, for a range of LI thresholds at different z scores. Results Measurement of hemispheric language dominance with rs-fMRI was highly concordant with task-fMRI results. Among the evaluated z scores for a range of LI thresholds, rs-fMRI yielded a maximum accuracy of 95%, a sensitivity of 83%, and specificity of 92.8% for z = 2 at 0.05 LI threshold. Conclusion The present study suggests that rs-fMRI networks obtained using ICA technique can be used as an alternative for task-fMRI language laterality. The novel aspect of the work is suggestive of optimal thresholds while applying rs-fMRI, is an important endeavor given that many patients with epilepsy have co-morbid cognitive deficits. Thus, an accurate method to determine language laterality without requiring a patient to complete the language task would be advantageous. Keywords Temporal lobe epilepsy. Language lateralization. Resting fMRI. Language-fMRI. Independent component analysis Abbreviations RS-fMRI resting-state functional magnetic resonance imaging TLE temporal lobe epilepsy ICA independent component analysis LI laterality index IAP intracarotid amobarbital procedure HCs healthy controls LTLE left temporal lobe epilepsy RTLE right temporal lobe epilepsy Electronic supplementary material The online version of this article (

Neurology India, 2022

Background: Prediction of outcome of West syndrome (WS) in relation to etiology and electrophysio... more Background: Prediction of outcome of West syndrome (WS) in relation to etiology and electrophysiology remain pertinent challenges. Objective: This study aimed to compare electro-clinical and imaging characteristics between WS of “unknown-etiology”; “symptomatic”WS; to gauge the evolution and impact of electroencephalographic (EEG) patterns on seizure outcomes. Materials and Methods: Electro-clinico-radiological data of 76 children with WS who were followed up for atleast 1 year was collected for reviewing clinical, therapeutic and EEG profiles (sub-typed as typical and modified hypsarrhythmia [HA]). Quantified seizure scores were assessed. Results: Among 76 children included in this retrospective analysis, 31 (40.8%) were of unknown-etiology and 45 (59.2%) were “symptomatic” (structural cause/developmental-encephalopathy). Children with symptomatic WS (p = 0.037), specifically with gliosis on imaging (p = 0.05) and typical HA (including the multifocal subtype; P = 0.023) were more likely to have other seizure types before onset of spasms and exhibit prior delay or regression in milestones (p = 0.017). There was negative correlation between time to diagnosis and reduction in seizure scores (r = -0.32; p = 0.005).Significant reduction was noted in seizure scores with pharmacotherapy, irrespective of etiology (P < 0.001 in unknown-etiology and symptomatic subgroups). Seizure freedom rates did not differ between typical and modified HA groups (p = 0.215) with a higher proportion of children with meaningful reduction in seizure scores in the former sub-group (p = 0.030). Children who failed to achieve seizure remission were more likely to exhibit developmental impairment (p = 0.019). Conclusions: Early diagnosis and initiation of optimal therapy is crucial towards improving outcome, irrespective of etiology (which impacts pre-spasm development) and HA subtypes.

Acta Scientific Neurology

Electric Source Imaging (ESI) is an emerging technique that identifies the source of brain electr... more Electric Source Imaging (ESI) is an emerging technique that identifies the source of brain electrical activity by utilizing the spatial and temporal components of EEG recorded on the scalp. ESI appears to be a promising methodology for epilepsy evaluation as well as other neurological disorders based on the present body of research; nevertheless, the precise clinical relevance of ESI localization remains to be explored. This review paper aims to present the basic theoretical aspects of ESI and its clinical applications along with the currently available softwares for implementing this cutting-edge technology by examining some of the key studies performed in the field, with emphasis given to clinical work published in the recent years.

Epilepsy & Behavior, 2006

We report two patients with medically refractory epilepsy who had MRI evidence of unilateral subc... more We report two patients with medically refractory epilepsy who had MRI evidence of unilateral subcortical nodular heterotopia and agenesis of corpus callosum. The abnormal hemisphere was small, whereas the contralateral normal hemisphere appeared large and crossed the midline. Although the normal hemisphere was initially mistaken for hemimegalencephaly, there were no typical radiological features. Moreover, the electroencephalographic abnormalities lateralized to the hemisphere showing heterotopia. Because contralateral hemispheric abnormalities like heterotopia, hemimicrencephaly, and hemimegalencephaly can occur in patients with hemispheric heterotopias, we emphasize the importance of careful scrutiny of the contralateral hemisphere in patients with unilateral heterotopia. Absence of typical radiological features and appropriately lateralized electroencephalographic abnormalities will help differentiate the two. This is crucial when planning epilepsy surgery.

Neurosurgery, Apr 1, 2023

INTRODUCTION: Usage of Electrocorticography (ECoG) is not clearly established. Robust evidence do... more INTRODUCTION: Usage of Electrocorticography (ECoG) is not clearly established. Robust evidence doesnot exist to support its regular usage in Long term Epilepsy associated tumors (LEATs) which constitutes approximately 25-35% cases of drug resistant epilepsy. METHODS: Prospective randomized controlled trial, including all patients operated for drug resistant epilepsy with non-eloquent area LEATs. Patients were randomized into 2 groups namely Group I (without usage of ECoG) and Group II (with ECoG usage). Group II patients further underwent tailored resections if necessary, as per ECoG practice protocols. Surgical outcomes were evaluated for seizure outcome (Engel scale) and adverse event profile. RESULTS: Total of 38 patients operated for LEATs having drug resistant epilepsy were included in the study with mean age of 21.1 years (range 2-46 years). 18 patients belonged to Group I and 20 patients belonged to Group II with mean follow-up period of 11.02 months (range 3-22 months). 30% patients (n = 6) in Group II underwent extended resection based on rhythmic persistent post resection spikes. 90% of Group II patients had Engel score Ia during follow up compared to 77.7% of Group I with Engel score Ia (p = 0.302). In Group II, 85.7% patients with extended tailored resection had Engel score Ia compared to 83.8% cases without extended resection (p = 0.904). CONCLUSIONS: Though ECoGs role may have been established in focal cortical dysplasia, its utility in LEATs is limited. Our randomized study confirmed that there is no added benefit conferred by the use of ECoG in LEATS. Additional tailored resections aided by ECoG also did not yield seizure outcome benefits in LEATS.

Epilepsy & Behavior

Isoform E2 of drebrin, an actin-binding protein originally identified in neuronal cells, has rece... more Isoform E2 of drebrin, an actin-binding protein originally identified in neuronal cells, has recently been identified in diverse non-neuronal cells, mostly in association with cell processes and intercellular junctions. Here, we report on the presence of drebrin in normal human skin, epithelial skin cancers, and cultured keratinocytes. Keratinocytes of normal epidermis contain almost no drebrin but the protein is readily seen in hair follicles. By immunohistochemistry and immunoblot, basal cell carcinomas (BCC) are rich in drebrin, and confocal laser scanning and immunoelectron microscopy show accumulation at adhering junctions, in co-localization with actin and partially with plaque proteins. In squamous cell carcinomas, keratoacanthomas, and in epidermal precancers, drebrin is heterogeneously distributed, appearing as mosaics. Primary keratinocyte cultures contain significant amounts of drebrin enriched at adhering junctions. When epithelium-derived cells devoid of drebrin are transfected with drebrin-enhanced green fluorescent protein, constructs accumulate in the cell periphery, and immunoprecipitation shows complexes with actin. During epidermal growth factor induced formation of cell processes, drebrin retains this junction association, as observed by live cell microscopy. Our results suggest novel functions of drebrin such as an involvement in cell-cell adhesion and tumorigenesis and a potential value in diagnosis of BCC.

Canadian Journal of Neurological Sciences, Jul 1, 2009

American Journal of Neuroradiology, Oct 22, 2015

BACKGROUND AND PURPOSE: Iron-mediated oxidative stress plays a pivotal role in the pathogenesis o... more BACKGROUND AND PURPOSE: Iron-mediated oxidative stress plays a pivotal role in the pathogenesis of amyotrophic lateral sclerosis. This study aimed to assess iron deposition qualitatively and quantitatively by using SWI and microstructural changes in the corticospinal tract by using DTI in patients with amyotrophic lateral sclerosis. MATERIALS AND METHODS: Seventeen patients with amyotrophic lateral sclerosis and 15 age-and sex-matched controls underwent brain MR imaging with SWI and DTI. SWI was analyzed for both signal-intensity scoring and quantitative estimation of iron deposition in the anterior and posterior banks of the motor and sensory cortices and deep gray nuclei. The diffusion measurements along the corticospinal tract at the level of pons and medulla were obtained by ROI analysis. RESULTS: Patients with amyotrophic lateral sclerosis showed reduced signal-intensity grades in the posterior bank of the motor cortex bilaterally. Quantitative analysis confirmed significantly higher iron content in the posterior bank of the motor cortex in patients with amyotrophic lateral sclerosis. In contrast, no significant differences were noted for the anterior bank of the motor cortex, anterior and posterior banks of the sensory cortex, and deep nuclei. Receiver operating characteristic comparison showed a cutoff of 35g Fe/g of tissue with an area under the curve of 0.78 (P ϭ .008) for the posterior bank of the motor cortex in discriminating patients with amyotrophic lateral sclerosis from controls. Fractional anisotropy was lower in the pyramidal tracts of patients with amyotrophic lateral sclerosis at the pons and medulla on either side, along with higher directionally averaged mean diffusivity values. The combination of SWI and DTI revealed an area under the curve of 0.784 for differentiating patients with amyotrophic lateral sclerosis from controls. CONCLUSIONS: Measurements of motor cortex iron deposition and diffusion tensor parameters of the corticospinal tract may be useful biomarkers for the diagnosis of clinically suspected amyotrophic lateral sclerosis. ABBREVIATIONS: ALS ϭ amyotrophic lateral sclerosis, CST ϭ corticospinal tract; D av ϭ directionally averaged mean diffusivity; FA ϭ fractional anisotropy; PBMC ϭ posterior bank of the motor cortex A myotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder of the motor system characterized by progressive degeneration of corticospinal tracts, brain stem, and lower motor neurons in the spinal cord. 1,2 The clinical presentation of ALS includes progressive involvement of the upper motor neu-ron, lower motor neuron, and craniobulbar musculature due to degeneration of the anterior horn cells and motor neurons. The disease shows great variation in its onset, clinical presentation, and survival, with diagnosis usually depending on changes in needle electromyography from various muscles sampled, which include even the tongue and paraspinal muscles. Needle electromyography is invasive and rather cumbersome to perform. Hence, a reliable and objective noninvasive surrogate biomarker of motor neuron dysfunction, if available, may play a pivotal role in the diagnosis and monitoring of disease progression in ALS. Recent investigations proved that ALS pathology is associated with abnormal iron homeostasis inducing excessive oxidative stress in the motor neurons. 3,4 There is also evidence to suggest that reduced fractional anisotropy (FA) and increased directionally averaged mean diffusivity (D av) along the pyra

Annals of Indian Academy of Neurology, 2022

Archives of Medicine and Health Sciences, 2022

Journal of Neuroradiology, Feb 1, 2018

Background and purpose.-The study evaluated the utility of arterial spin labeling (ASL) perfusion... more Background and purpose.-The study evaluated the utility of arterial spin labeling (ASL) perfusion imaging in Rasmussen's encephalitis (RE). Material and methods.-The hospital electronic database was searched using the search words "encephalitis," "autoimmune encephalitis" and "Rasmussen's encephalitis" for the period of 1 Jan 2015 to 31 Jan 2017. Clinically diagnosed cases of RE for which epilepsy protocol magnetic resonance imaging (MRI) with perfusion imaging (ASL) performed on a 3T scanner were retrieved. The diagnosis of RE was based on Bien's criteria (Bien et al., 2005). We obtained patient's demographic details, clinical features, electrophysiological studies, and follow-up data from electronic hospital records. Results.-We included nine patients with RE of whom seven patients showed increased perfusion, and two patients decreased perfusion. Among these patients, MRI changes of gyral hyperintensity without volume loss corresponded to regional ASL hyperperfusion in six patients and ASL hypoperfusion in one patient. Two patients who showed ASL hypoperfusion had corresponding atrophy on MRI. Eight patients of RE had epilepsia partialis continua (EPC) or daily seizures, and one patient was seizure-free postsurgery. Five patients showed a concordance of ASL hyperperfusion with clinical ictal onset zone. Among the seven patients with ASL hyperperfusion, the finding was concordant (complete or partial) with the electroencephalogram (EEG) ictal onset zone in six patients and with interictal epileptiform discharge (IED) in seven patients. Conclusion.-Increased perfusion in ASL of the involved brain parenchyma in RE is a common MRI finding and may be due to either active inflammation of the brain involved or a seizure-related finding.