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Biomedical subjects

K Radhakrishnan

Publications and source records attributed to K Radhakrishnan.

At least 55 records · Page 3Linked to original sources
PubMed1998

Prevalence of photoparoxysmal response among South Indian epilepsy patients.

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.

Action Potentials↗
PubMed1998

Predictors of outcome of anterior temporal lobectomy for intractable epilepsy: a multivariate study.

OBJECTIVE: To identify presurgical and postsurgical factors that are independently predictive of the outcome of anterior temporal lobectomy (ATL) for intractable epilepsy. BACKGROUND: There have been reports of prognostic factors in epilepsy surgery, but little is known about factors that independently predict outcome of ATL. METHODS: We studied 175 consecutive ATL patients who had at least 2 years of postsurgical follow-up. Significant factors on univariate analyses were subjected to stepwise logistic regression analysis. RESULTS: On univariate analyses, two presurgical conditions were significantly associated with excellent seizure control at last follow-up: (1) unilateral hippocampal formation atrophy as detected on MRI and (2) all scalp interictal epileptiform discharges concordant with the location of ictal onset (p < 0.05). Three postsurgical factors that occurred during the first year were associated with excellent seizure outcome: the absence of interictal epileptiform discharges at 3 months, complete seizure control, and having only nondisabling seizures for those who did not become seizure free. Logistic regression analysis revealed the following to be independently predictive of excellent seizure control: MRI-detected unilateral hippocampal formation atrophy, concordant interictal epileptiform discharges, complete seizure control during the first postsurgical year, and having only nondisabling seizures during the first postsurgical year for those who did not become seizure free. CONCLUSIONS: Presurgical identification of unilateral hippocampal formation atrophy, or of interictal epileptiform discharges that are all concordant with the location of ictal onset, predict excellent outcome of ATL. However, the probability of excellent outcome is highest (94%) when both factors are present.

Adolescent↗
PubMed1998

Acute postoperative seizures following anterior temporal lobectomy for intractable partial epilepsy.

OBJECT: Recurrence of seizures immediately following epilepsy surgery can be emotionally devastating, and raises concerns about the chances of successfully attaining long-term seizure control. The goals of this study were to investigate the frequency of acute postoperative seizures (APOS) occurring in the 1st postoperative week following anterior temporal lobectomy (ATL) to identify potential risk factors and to determine their prognostic significance. METHODS: One hundred sixty consecutive patients who underwent an ATL for intractable nonlesional temporal lobe epilepsy were retrospectively studied. Acute postoperative seizures occurred in 32 patients (20%). None of the following factors were shown to be significantly associated with the occurrence of APOS: age at surgery, duration of epilepsy, side of surgery, extent of neocortical resection, electrocorticography findings, presence of mesial temporal sclerosis, and hippocampal volume measurements (p > 0.05). Patients who suffered from APOS overall had a lower rate of favorable outcome with respect to seizure control at the last follow-up examination than patients without APOS (62.5% compared with 83.6%, p < 0.05). The type of APOS was of prognostic importance, with patients whose APOS were similar to their preoperative habitual seizures having a significantly worse outcome than those whose APOS were auras or were focal motor and/or generalized tonic-clonic seizures (excellent outcome: 14.3%, 77.8%, and 75%, respectively, p < 0.05). Only patients who had APOS similar to preoperative habitual seizures were less likely to have an excellent outcome than patients without APOS (14.3% compared with 75%, p < 0.05). Timing of the APOS and identification of a precipitating factor were of no prognostic importance. CONCLUSIONS: The findings of this study may be useful in counseling patients who suffer from APOS following ATL for temporal lobe epilepsy.

Acute Disease↗
PubMed1998

Mitochondrial myopathies--a clinicopathological study.

Mitochondrial myopathies are heterogeneous group of clinical disorders that can affect multiple systems besides skeletal muscles. The mitochondrial abnormalities in the skeletal muscles are morphologically identified by the presence of characteristic Ragged-red fibers (RRF) in the cryostat sections of the muscle stained with modified Gomori's trichrome stain. In this retrospective study, clinical and histopathological features in six patients with mitochondrial myopathies have been analysed. The utility of histochemical methods in confirming the diagnosis of mitochondrial myopathy has been emphasised.

Adolescent↗
PubMed1997

Assessing changes over time in temporal lobectomy: outcome by scoring seizure frequency.

Current methods of evaluating seizure outcome after anterior temporal lobectomy (ATL) have major limitations. We evaluated the usefulness of a recently proposed system in our study of the stability of seizure frequency after ATL in 184 patients with intractable epilepsy. Data collection by chart review was supplemented by an intensive program of follow-up by our survey research center through correspondence or phone calls according to a protocol approved by our Institutional Review Board. Seizure frequency during each 12-month period after ATL was scored for each patient. The only statistically significant change in seizure frequency scores during follow-up was between the third and the fourth years (means of 2.61 and 2.11; P < 0.045). Further assessment showed that the change was most likely due to an increase in the proportion of patients who achieved a score of 0 when they successfully stopped taking antiepileptic medications (9.1% in the third year and 22.5% in the fourth year; P < 0.05). There was no statistically significant difference between follow-up years in the proportion of patients achieving excellent outcome (i.e. scores of 0-4). Outcome remained unchanged when follow-up at each year was confined to the same patients throughout their postsurgical course. By using the Seizure Frequency Scoring System, we have demonstrated that seizure outcome remains stable after ATL. The scoring system facilitates the detection of subtle changes in the postoperative course. The advantages and the limitations of the system are discussed.

Adult↗
PubMed1997

Inflammatory myopathies--a clinicopathologic study.

In this study, clinical, histopathological and immunological profiles were analysed in ten patients with inflammatory myopathies. Polymyositis and dermatomyositis were more common than other forms of inflammatory myopathies. The pathogenetic mechanisms and distinguishing histopathological and immunological profiles between polymyositis and dermatomyositis have been highlighted.

Adolescent↗
PubMed1996

Ipsilateral independent periodic lateralized epileptiform discharges.

We have identified a previously unreported subtype of periodic lateralized epileptiform discharge (PLED) characterized by periodic discharges arising from ipsilateral independent foci. All 4 patients had acute cerebral lesions, and 3 of them had focal motor seizures with secondary generalization. The site of localization of the PLEDs corresponded to the boundaries of the underlying structural lesion or lesions, and this, together with the variable temporal relationship between them, supports a cortical origin for PLEDs associated with underlying lesions. the spatial and temporal independence of these periodic discharges in combination with their association with (1) acute cerebral lesions. (2) altered consciousness and seizures, and (3) resolution with time leads us to propose the term "IpsiIPs" to describe this subtype of PLEDs.

Aged↗
PubMed1996

Neurologic complications of infective endocarditis observed in a south Indian referral hospital.

We retrospectively reviewed the records of 110 patients with infective endocarditis (IE) who were hospitalized between 1977 and 1994 at a tertiary referral center in Southern India to assess the occurrence of neurologic complications and the factors that contribute to their development, and to compare our experience from a developing country with the reported data from developed countries. There were 62 males and 48 females, aged 0.6-59 (mean 24.0) years. Rheumatic heart disease (RHD) was the most frequent underlying cardiac lesion accounting for 65 (59.1%) patients. Neurologic complications were observed in 58 (52.7%) patients: cerebral embolism was the most frequent (23 patients). Thirty-five (31.8%) patients died. Mortality in the group with neurologic complications (41.4%) was significantly higher than in the group without (21.2%) (p = 0.04). The duration of symptoms prior to the diagnosis was longer in the group with neurologic complications, mean 174.9 versus 95.6 days (p = 0.03). We conclude that (1) IE occurs at younger ages in the Third World and RHD still constitute the major underlying heart disease; (2) in spite of the differences in the general aspects of IE between developed and developing nations, the frequency and gravity of neurologic complications are similar, (3) mortality is significantly increased in patients with neurologic complications; and (4) delay in the diagnosis of IE contributes to the development of neurologic complications.

Adolescent↗
PubMed1996

Periodic electroencephalographic pattern in subacute sclerosing panencephalitis modified by preexisting damaged cerebral hemisphere.

We report a 15 year old girl with a childhood hemiplegia, who developed a recent progressive intellectual decline associated with elevated globulins and measles antibody titres in the cerebrospinal fluid, indicating a diagnosis of subacute sclerosing panencephalitis (SSPE). The magnetic resonance imaging revealed left hemispheric atrophy concordant with a long-standing right hemiplegia, and electroencephalography exhibited lateralized periodic complexes (PCs) over the right hemisphere concordant with left-sided myoclonic jerks. The modification of PCs in our patient due to preexisting damaged cerebral hemisphere illustrate that a fairly functional cortex and subcortical white matter are needed for the expression of the PCs of SSPE.

Adolescent↗
PubMed1996

Response to thymectomy in South Indian patients with myasthenia gravis.

AIMS: The rate of remission among patients with myasthenia gravis (MG) following thymectomy and the predictors of the outcome have revealed vast variation in studies from different geographic regions raising suspicion about the influence of ethnic factors. MATERIAL & METHODS: We retrospectively evaluated the outcome of 71 South Indian MG patients who were thymectomized between 1987 through 1993 and analyzed the relationship between clinical and histopathological features and postthymectomy outcome. RESULTS: The clinical severity of the disease did not differ between the 29 patients with and 42 patients without a thymoma. Seventynine percent of our patients responded favourably to thymectomy; without additional immunosupression therapy, 52% achieved a near-complete remission. An younger age and milder disease correlated with a good outcome. Patients with thymoma responded as favourably as those without a thymoma. CONCLUSIONS: The postthymectomy response of South Indian MG patients in general did not differ from that of Western and Oriental patients.

Adolescent↗
PubMed1996

Detection of Campylobacter jejuni/C.coli infection in patients with Guillain-Barré syndrome by serology and culture.

Serum samples from 43 cases of Guillain-Barré Syndrome (GBS), 32 non-GBS neurology patients, and 35 healthy persons from a medical institute in Kerala, India, were tested for antibody levels against a Campylobacter jejuni strain Penner serotype 0:19 by agglutination and ELISA. Twenty-six percent of samples from GBS cases showed high antibody levels in all assays. Of 8 stool samples of new GBS cases examined by culture, 38% were positive for C. jejuni/C. col1. The results suggest that at least a quarter of GBS cases studied were associated with Campylobacter infection.

Adolescent↗
PubMed1996

Study on the feasibility of delineating mosquitogenic conditions in and around Delhi using Indian Remote Sensing Satellite data.

A feasibility study to identify mosquitogenic conditions in six study sites in and around Delhi (Bhalaswa lake, Nazafgarh drain, Seelampur lake, Sanjay lake, Okhla barrage and Hindon barrage) using Indian Remote Sensing Satellites was carried out. The water bodies with marshy areas, vegetation and human settlements were considered as environmental variables responsible for mosquitogenic conditions. Multidate IRS 1A and B, LISS-II satellite data were collected and analysed on Vax 11/780 computers. False colour composite (FCC) images were generated and land cover assessed using supervised classification based on ground truth training sets. Ground truth validation of satellite data was done on satellite pass dates. Concurrent monitoring of larval and adult mosquito density was performed by selecting sub-sites in each study site. The results indicate that mosquitogenic conditions can be identified (with limitation of resolution, i.e. 36.5 m) using FCC images and these images can be used as base maps of study sites. Characterization of study sites based on land cover was done from the view point of mosquitogenic conditions. Spatial changes in mosquito density vis-a-vis changes in environmental variables revealed positive correlation with water bodies and vegetation in some study sites.

Animals↗
PubMed1995

The trends in incidence of primary brain tumors in the population of Rochester, Minnesota.

A number of reports have suggested an increasing incidence of primary brain tumors, especially malignant astrocytomas, in the elderly population. To investigate this issue, we analyzed the incidence and temporal trends of primary intracranial neoplasms diagnosed in the population of Rochester, Minnesota, over the 40 years between 1950 and 1990. The incidence of symptomatic primary brain tumors (excluding patients diagnosed incidentally at autopsy and by neuroimaging studies) increased from 9.5 per 100,000 population per year in 1950 to 1969 to 12.5 per 100,000 per year in 1970 to 1989; this change was not statistically significant (chi 2 trend, 1.89; p = 0.17). While the incidence of pituitary adenomas increased significantly between the two periods (chi 2 trend, 4.44; p = 0.04), the incidence trends of all gliomas, malignant astrocytomas, and meningiomas showed no change among persons younger than 65 years as well as those 65 years and older. The number of patients incidentally found to have neoplasms by neuroimaging studies increased in the recent 20-year period (chi 2 trend, 4.08; p = 0.04). The average age- and sex-adjusted incidence rates per 100,000 per year during the study period in the population of Rochester, Minnesota, for symptomatic tumors were 5.0 for all gliomas, 3.3 for malignant astrocytomas, 2.0 for meningiomas, and 2.4 for pituitary adenomas. In conclusion, our data indicate that the reported increase in the incidence of primary brain tumors is an artifact of improvement in diagnostic technology and practice.

Adenoma↗
PubMed1995

The significance of the phi rhythm.

We reviewed two series of patients with the phi rhythm (posterior rhythmic slow waves occurring after eye closure) to determine its characteristics and clinical significance. Phi rhythm was defined as a minimum of three consecutive monomorphic posterior delta waves occurring within 2 sec of eye closure on at least two occasions during electroencephalography. Group 1 consisted of 30 patients (16 male and 14 female) with a mean age of 11.6 +/- 8.4 years (range, 3 to 46 years) who were evaluated between 1978 and 1993. Phi rhythm most commonly occurred when the patient was alert and after concentrated visual attention, such as reading or picture or pattern scanning. Seventeen of these patients had epilepsy (11 generalized, 3 focal, 1 both, and 2 unclassified). The frequency of epilepsy was not significantly different from that of a control group of 60 patients matched for age and sex; however, generalized epilepsies were more common in the phi group (P = 0.008). Group 2 consisted of a previously unreported series of 121 patients evaluated between 1960 and 1962. A diverse range of underlying clinical diagnoses was evident in both groups. The mechanism of the phi rhythm is unknown, but the findings suggest that the origin is subcortical and that the presence of this activity should not be considered diagnostic of a seizure disorder.

Adolescent↗
PubMed1995

Reading epilepsy. An appraisal of 20 patients diagnosed at the Mayo Clinic, Rochester, Minnesota, between 1949 and 1989, and delineation of the epileptic syndrome.

The clinical and EEG findings in 20 patients with reading epilepsy (RE) diagnosed at the Mayo Clinic, Rochester, Minnesota, between 1949 and 1989 are documented in this study. Sixteen patients were followed for more than 10 years. The age at onset of RE ranged from 10 to 46 years (median 17.5 years). Precipitating factors other than reading, involving linguistic or non-linguistic higher cognitive processes, occurred in nine patients. Spontaneous myoclonus affecting the upper extremities, especially in the morning, indicated co-occurrence of juvenile myoclonic epilepsy (JME) in four patients. A positive family history for seizures (including one person with RE) was obtained for four patients. Interictal EEG abnormalities were present in 12 patients (60%). Ictal EEG findings were generalized and symmetric in 75% of patients, with a strictly focal (temporoparietal) discharge occurring in only two patients. Of the 11 patients who were alive and for whom recent information regarding seizure status was available, only three were symptom-free without anticonvulsant medication. Our data indicate resemblance of the clinical manifestations of RE with JME and other cognitive function-related seizures and point toward an overlap with them. We propose a classification for higher cognitive function-related epilepsies in general and RE in particular to explain the electrographic heterogeneity and clinical overlap observed. A hypothetical model to explain the ictogenesis and to encompass the electroclinical heterogeneity in RE is suggested.

Adolescent↗
PubMed1994

Idiopathic intracranial hypertension.

OBJECTIVE: This review was undertaken to summarize the significant progress that has been made in the epidemiology of idiopathic intracranial hypertension (IIH), the changing nosology, and the diagnostic criteria and therapeutic strategy. DESIGN: We reviewed the pertinent literature on IIH published in major English-language journals for the last 20 years. MATERIAL AND METHODS: The diagnosis, epidemiology, pathophysiology, complications, and treatment of IIH are described. RESULTS: IIH occurs at an average annual incidence rate per 100,000 persons of 1 to 2 for the total population and 19 to 21 in obese females of the reproductive age-group. IIH is a recognized cause of reversible vision loss in adult obese women. The diagnosis of IIH requires a documented elevation of intracranial pressure, normal cerebrospinal fluid (CSF) composition, and normal findings on neuroimaging studies. At least two primary mechanisms for the development of increased CSF pressure in IIH have been postulated and supported by experimental data: vasogenic extracellular brain edema and a low conductance of CSF outflow at the arachnoid villi. This condition may be secondarily exacerbated by compression of intracranial venous sinuses by the increased intracranial pressure, resulting in a further reduction of flow across the arachnoid villi. The therapeutic strategy is determined by visual status, which needs close monitoring. CONCLUSION: Although medical measures to lower the intracranial hypertension are successful in the majority of patients, surgical therapy should not be delayed in those with significant or progressive vision loss. Based on recent advances, a practical approach has been described for the diagnosis, early detection of visual impairment, and targeting therapy to preserve the vision or to reverse recent loss of vision in patients with IIH.

Adolescent↗
PubMed1994

Epidemiology of cervical radiculopathy. A population-based study from Rochester, Minnesota, 1976 through 1990.

An epidemiological survey of cervical radiculopathy in Rochester, Minnesota, 1976-90, through the records-linkage system of the Mayo Clinic ascertained 561 patients (332 males and 229 females). Ages ranged from 13 to 91 years; the mean age +/- SD was 47.6 +/- 13.1 years for males and 48.2 +/- 13.8 years for females. A history of physical exertion or trauma preceding the onset of symptoms occurred in only 14.8% of cases. A past history of lumbar radiculopathy was present in 41%. The median duration of symptoms prior to diagnosis was 15 days. A monoradiculopathy involving C7 nerve root was the most frequent, followed by C6. A confirmed disc protrusion was responsible for cervical radiculopathy in 21.9% of patients; 68.4% were related to spondylosis, disc or both. During the median duration of follow-up of 4.9 years, recurrence of the condition occurred in 31.7%, and 26% underwent surgery for cervical radiculopathy. A combination of radicular pain and sensory deficit, and objective muscle weakness were predictors of a decision to operate. At last follow-up 90% of our population-based patients were asymptomatic or only midly incapacitated due to cervical radiculopathy. The average annual age-adjusted incidence rates per 100,000 population for cervical radiculopathy in Rochester were 83.2 for the total, 107.3 for males and 63.5 for females. The age-specific annual incidence rate per 100,000 population reached a peak of 202.9 for the age group 50-54 years.

Adolescent↗