Browsing by Author "Nayak, SD"
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Item A multi-level wavelet approach for automatic detection of epileptic spikes in the electroencephalogram(COMPUTERS IN BIOLOGY AND MEDICINE, 2008) Indiradevi, KP; Elias, E; Sathidevi, PS; Nayak, SD; Radhakrishnan, KWe describe a strategy to automatically identify epileptiform activity in 18-channel human electroencephalogram (EEG) based on a multi-resolution, multi-level analysis. The signal on each channel is decomposed into six sub-bands using discrete wavelet transform. Adaptive threshold is applied on sub-bands 4 and 5. The spike portion of EEG signal is then extracted from the raw data and energy of the signal for locating the exact location of epileptic foci is determined. The key points of this process are identification of a suitable wavelet for decomposition of EEG signals, recognition of a proper resolution level, and computation of an appropriate dynamic threshold. (c) 2008 Elsevier Ltd. All rights reserved.Item Antiepileptic pharmacotherapy: Prevalence of polytherapy and its implications(NEUROLOGY INDIA, 1998) Radhakrishnan, K; Nayak, SDItem Epilepsy surgery in a developing country(11TH INTERNATIONAL CONGRESS OF NEUROLOGICAL SURGERY, VOLS 1 AND 2, 1997) Rao, MB; Radhakrishnan, K; Thomas, SV; Nayak, SD; Santoshkumar, BWe performed a prospective study of 55 consecutive patients who underwent anterior temporal lobectomy and amygdalo-hippocampectomy (ATL) for intractable complex partial seizures (CPS) of temporal lobe origin. Presurgical evaluation included detailed clinical history and examination, scalp EEG, video-EEG, MRI, intracarotid amytal test, neuropsychological, psyche-social and psychiatric evaluation. Three-months and 1-year post-ATL assessment revealed a remarkable improvement in outcome scores; nearly 96% patients are either totally free or almost free of seizures (Engel class I and II). Utilizing non-invasive evaluation, patients with intractable temporal lobe epilepsy can be selected for cost-effective surgical treatment to provide good seizure control and improved quality of life.Item Ischaemic stroke in the young adult: Clinical features, risk factors and outcome(NATIONAL MEDICAL JOURNAL OF INDIA, 1997)Background. Stroke is an important cause of morbidity and mortality in young adults, especially in developing countries. This study aimed to evaluate the clinical features, risk factors and outcome of ischaemic stroke in young adults aged 15-45 years.Methods. A retrospective review was done of the medical records of 177 patients seen in a tertiary referral centre in Thiruvananthapuram, Kerala between January 1988 and Anarch 1994.Results. There were 135 males and 42 females with a mean (SD) age of 34.7 (8) years at onset of stroke. An aetiological categorization of stroke was obtained in 111 (63%) patients and it was uncertain or unknown in the rest. Athero-thrombotic stroke and cardio-embolic stroke occurred in 24% and 17%, respectively. Hypertension, smoking, hypertipidaemia and athero-thrombotic stroke were significantly more prevalent in the 31-45 year age group competed to the 15-30 year age group. There was only one patient with postpartum intracranial sinovenous thrombosis. At a mean follow up of 7 months (range 1-62 months), 75% of the patients were independent or only mildly disabled. The case-fatality rate was 1%.Conclusion. Ischaemic stroke in the young adult is more frequent in males. The aetiopathogenesis can be determined in the majority and the athero-thrombotic process predominates. The mortality is negligible and the functional outcome is good in most patients.Item Longitudinal CT and MR appearances of hemimegalencephaly in a patient with tuberous sclerosis(CHILDS NERVOUS SYSTEM, 2008) Balaji, R; Kesavadas, C; Ramachandran, K; Nayak, SD; Priyakumari, TCase report A 3-day-old baby was referred to our institution with seizures since birth and a presumptive diagnosis of cerebral tumor detected by prenatal ultrasound. Computed tomography (CT) and Magnetic Resonance (MR) imaging performed immediately after birth revealed the presence of an enhancing mass in the left cerebral hemisphere. Discussion The possibility of a congenital malignant brain tumor was considered. Although surgery was advised, the parents opted for conservative medical management. The infant was under treatment for seizures with antiepileptic drugs. At 7-month follow-up, there was a noticeable increase in the seizure activity with signs of developmental delay and increased head circumference. Repeat CT and MR imaging showed features of hemimegalencephaly with a calcified mass involving the left hemisphere. The patient was diagnosed to have tuberous sclerosis. This case report illustrates how an enhancing mass (possibly a tuber) over a period of time diminishes in size and becomes calcified in a patient with tuberous sclerosis and associated hemimegalencephaly.Item Prevalence of photoparoxysmal response among South Indian epilepsy patients(SEIZURE-EUROPEAN JOURNAL OF EPILEPSY, 1998)The reported geographical variations in the prevalence of photoparoxysmal response (PPR) among epilepsy patients have been variously attributed to methodological problems such as patient selection, technique of intermittent photic stimulation (IPS) and definition of PPR, and environmental and racial factors. We determined the prevalence rate of PPR among South Indian epilepsy patients and compared it with the rates reported from elsewhere. Twenty of our 575 patients had a PPR, a prevalence ratio of 3.5%, which is in striking contrast to the 0.6% reported for North Indian epilepsy patients. Environmental and racial factors cannot explain the difference in the prevalence rates of PPR between South and North Indian epilepsy patients. We conclude that the demographic characteristics of the patient group, such as age and gender, the epilepsy type, sleep deprivation, technique of IPS and definition of PPR, greatly influence the prevalence rate of PPR.Item Profile of antiepileptic pharmacotherapy in a tertiary referral center in South India: A pharmacoepidemiologic and pharmacoeconomic study(EPILEPSIA, 1999)Purpose: To study the current pharmacotherapy practices of epilepsy and its economics in a developing country by correlating the epidemiology and economics of antiepileptic drug (AED) treatment in general epilepsy care and comprehensive epilepsy care.Methods: We compared the AED-use profiles, efficacy, and tolerability at entry and at last follow-up for 972 patients seen at a comprehensive epilepsy clue program in South India from 1993 to 1995. The relative cost was expressed as the average percentage of the per capita gross national product (GNP/capita) each individual spent for AED treatment.Results: At entry, 562 (57.8%) subjects were receiving polytherapy; at last follow-up, 743 (76.4%) patients were receiving monotherapy, an increase of 34.3% in the use of monotherapy. One or more adverse drug reactions were reported by 28.6% of patients at entry and by 19.8% at last follow-up. The proportion of patients who were seizure free increased from 29.0 to 44.8%. Carbamazepine (CBZ) was the most frequently used AED, followed by diphenylhydantoin (DPH), valproate (VPA), and phe nobarbitone (PB). The relative cost (% GNP/capita) for standard AEDs were as follows: PB, 4.4%; DPH, 7.1%; CBZ, 16.8%; and VPA, 29.5%. The average annual cost of AED treatment per patient in U.S. dollars was $64.32 at entry and $47.73 at last follow-up. Reduction in polytherapy resulted in the net annual saving of $16,128 ($16.59 per patient, or 5.4% GNP/capita).Conclusions: The more frequent use of relatively expensive drugs like CBZ and VPA and the use of polytherapy-still quite prevalent in developing countries-has escalated the cost of AED therapy. Although in recent years AEDs have become more available in developing regions, primary and secondary care physicians have not been adequately educated about the current trends in the pharmacotherapy of epilepsy.Item Simultaneous traumatic brachial plexopathy and cervical root avulsion(AMERICAN JOURNAL OF ELECTRONEURODIAGNOSTIC TECHNOLOGY, 2001) Kuruvilla, A; Nayak, SD; Joseph, SWe report a 38-year-old man who sustained combined brachial plexus injury and cervical root avulsion after a fall. Such combined injuries are not very common and the diagnosis of a combined lesion needs a high index of suspicion. The electrophysiological evaluation of a brachial monoplegia showing absent sensory nerve action potentials (SNAPs) and denervation in the appendicular muscles confirm a lesion distal to dorsal root ganglion. If the study is terminated at this point, a co-existing preganlionic lesion can be easily missed due to the exclusion of cervical paraspinal muscles during electromyography (EMG). This report emphasizes that in every instance of a traumatic brachial plexopathy, an additional preganglionic lesion like a root avulsion must be suspected and may be carefully evaluated by means of electrophysiologic techniques and myelographic computerized axial tomography (MCT) scan or magnetic resonance imaging (MRI). A brief review of neuroimaging techniques and their correlation with electrodiagnostic findings in cervical root avulsion is also presented.Item Untitled - Reply(EPILEPSIA, 1999) Radhakrishnan, K; Nayak, SD; Kumar, SP; Sarma, PS