Ruchi Kothari

Neurophysiologic findings in children with spastic cerebral palsy

Context: Cerebral palsy (CP) is a heterogeneous group of permanent, non-progressive motor disorders of movement and posture caused by chronic brain injuries. It is the most common cause of physical disability in childhood; spastic cerebral palsy being the most prevalent of its various forms. There is scanty information about the neurophysiologic investigations in children diagnosed as having spastic CP. Aims: The aim of the study was to investigate the relationship between abnormal VEP and BAEP findings with different clinical parameters in children with spastic cerebral palsy. Materials and Methods: Fifteen children with spastic CP in the age range 4 months to 10 years participated in this study. Evaluation of VEPs, brainstem evoked potentials (BAEPs) were performed in all study patients as well as 35 healthy children as controls. The study was conducted after obtaining ethics committee approval and informed consent of parents. Statistical Analysis Used: Significance of difference in the mean values of different parameters in different groups was assessed by Student’s “t” test and the P value <0.05 was considered to be significant. All the values were expressed as mean ± 1 Std. Deviation. Results: A significant difference was found in the VEP latencies and amplitude between the subjects with CP and controls. Striking BAEP abnormalities in CP patients include prolongation of absolute latency of wave V, interpeak latencies of III-V and lowered I-V ratio. Abnormal VEPs and BAEPs in children with bilateral spastic cerebral palsy demonstrated a correlation with the presence of moderate to severe developmental delay. Conclusions: The differences in VEPs and BAEPs were determined between CP children and healthy children. The abnormalities found are probably linked to the neurological deficits present in cases of cerebral palsy.

Correlation of pattern reversal visual evoked potential parameters with the pattern standard deviation in primary open angle glaucoma

AIM To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation (PSD) of Humphrey visual field could be associated with visual evoked potential (VEP) parameters of patients having primary open angle glaucoma (POAG). METHODS Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential (PRVEP) were assessed in 100 patients with POAG. The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated (full field) and displayed on VEP monitor (colour 14″) by an electronic pattern regenerator inbuilt in an evoked potential recorder (RMS EMG EP MARK II). RESULTS The results of our study indicate that there is a highly significant (P<0.001) negative correlation of P100 amplitude and a statistically significant (P<0.05) positive correlation of N70 latency, P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Students t-test. CONCLUSION Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values. Conversely, as PSD increases the magnitude of VEP excursions were found to be diminished.

Significance of Visual Evoked Potentials in the Assessment of Visual Field Defects in Primary Open-Angle Glaucoma: A Review

Visual evoked potentials is an important visual electrophysiological tool which has been used for the evaluation of visual field defects in primary open-angle glaucoma and is an appropriate objective measure of optic nerve function. Significant correlations between the magnitude of the VEP parameters and MD of Humphrey static perimetry suggest that the impaired visual cortical responses observed in glaucoma patients can be revealed by both electrophysiological and psychophysical methods. In addition, the severity of global glaucomatous damage evidenced by reduction in MD could depend on the delay in neural conduction from retina to the visual cortex as revealed by the significant correlation between VEP latencies and MD which also supports the validity of the VEP testing in progression of glaucoma.

A Comprehensive Review on Methodologies Employed for Visual Evoked Potentials

Visual information is fundamental to how we appreciate our environment and interact with others. The visual evoked potential (VEP) is among those evoked potentials that are the bioelectric signals generated in the striate and extrastriate cortex when the retina is stimulated with light which can be recorded from the scalp electrodes. In the current paper, we provide an overview of the various modalities, techniques, and methodologies which have been employed for visual evoked potentials over the years. In the first part of the paper, we cast a cursory glance on the historical aspect of evoked potentials. Then the growing clinical significance and advantages of VEPs in clinical disorders have been briefly described, followed by the discussion on the earlier and currently available methods for VEPs based on the studies in the past and recent times. Next, we mention the standards and protocols laid down by the authorized agencies. We then summarize the recently developed techniques for VEP. In the concluding section, we lay down prospective research directives related to fundamental and applied aspects of VEPs as well as offering perspectives for further research to stimulate inquiry into the role of visual evoked potentials in visual processing impairment related disorders.

Influence of visual angle on pattern reversal visual evoked potentials

Purpose: The aim of this study was to find whether the visual evoked potential (VEP) latencies and amplitude are altered with different visual angles in healthy adult volunteers or not and to determine the visual angle which is the optimum and most appropriate among a wide range of check sizes for the reliable interpretation of pattern reversal VEPs (PRVEPs). Materials and Methods: The present study was conducted on 40 healthy volunteers. The subjects were divided into two groups. One group consisted of 20 individuals (nine males and 11 females) in the age range of 25-57 years and they were exposed to checks subtending a visual angle of 90, 120, and 180 minutes of arc. Another group comprised of 20 individuals (10 males and 10 females) in the age range of 36-60 years and they were subjected to checks subtending a visual angle of 15, 30, and 120 minutes of arc. The stimulus configuration comprised of the transient pattern reversal method in which a black and white checker board is generated (full field) on a VEP Monitor by an Evoked Potential Recorder (RMS EMG. EPMARK II). The statistical analysis was done by One Way Analysis of Variance (ANOVA) using EPI INFO 6. Results: In Group I, the maximum (max.) P100 latency of 98.8 ± 4.7 and the max. P100 amplitude of 10.05 ± 3.1 μV was obtained with checks of 90 minutes. In Group II, the max. P100 latency of 105.19 ± 4.75 msec as well as the max. P100 amplitude of 8.23 ± 3.30 μV was obtained with 15 minutes. The min. P100 latency in both the groups was obtained with checks of 120 minutes while the min. P100 amplitude was obtained with 180 minutes. A statistically significant difference was derived between means of P100 latency for 15 and 30 minutes with reference to its value for 120 minutes and between the mean value of P100 amplitude for 120 minutes and that of 90 and 180 minutes. Conclusion: Altering the size of stimulus (visual angle) has an effect on the PRVEP parameters. Our study found that the 120 is the appropriate (and optimal) check size that can be used for accurate interpretation of PRVEPs. This will help in better assessment of the optic nerve function and integrity of anterior visual pathways.

Association of Height With Pattern Reversal Visual Evoked Potentials.

PurposeThis study was conducted to investigate whether pattern reversal visual evoked potential parameters in a large sample of healthy subjects are influenced by height of the subjects. DesignIt was an institutional, cross-sectional study. MethodsPattern reversal visual evoked potential (PRVEP) recordings from 400 eyes from 200 normal subjects were performed in the Neurophysiology unit of the Department of Physiology in accordance to the standardized methodology and montages were kept as per 10–20 International System of electroencephalogram electrode placements. VEP latencies, duration and amplitude were measured in all subjects. The correlation of all the electrophysiological parameters with height was evaluated by Pearson’s correlation co-efficient (r) and its statistical significance was evaluated. ResultsOn correlating mean height with mean VEP parameters of both eyes in the subjects it was found that there is a positive correlation of P100 latency and N155 latency in the subjects and a highly significant negative correlation of P100 amplitude with height in the subjects of various age groups. N70 latency was found to be significantly positively correlated with height whereas P100 Duration showed a non-significant negative correlation with height of the subjects. ConclusionOur findings suggest that VEP latencies, duration and amplitude are influenced by the height of the individual. The positive correlation between VEP latencies and increasing height may all reflect the increase in length between the optic nerve head and the visual processing areas-the striate and the extra striate cortex which are the main generators of the various PRVEP waveforms.

Impact of spectral severity of alcoholism on visual-evoked potentials: A neuropsychiatric perspective

Background: The deleterious effects of alcohol on the brain are replete in literature. Only a few neurophysiologic measures can pick up the neuronal dysfunctions, one of them being visual-evoked potential (VEP). A very limited amount of data exists on the progression of neural abnormalities related to the spectral severity of alcoholism. Aim of the Study: To evaluate the impact of spectral severity of alcoholism through VEP and to understand the emergence of any specific pattern or morphometric abnormalities related to alcohol-induced neuropsychiatric presentations. Methodology: A total of 90 cases were recruited in addition to 180 age- and sex-matched controls using purposive and random sampling. The Structured Clinical Interview for DSM-IV Axis I Disorders, Clinician Version and Campbell Neuropsychiatric Inventory were used to evaluate alcohol disorders and its neuropsychiatric complications apart from the mandatory consultant-specific clinical evaluations of all the cases. Of 90 cases of alcohol dependence, 15 patients were currently abstinent for >6 months, 15 had alcohol intoxication, 15 had signs of alcohol withdrawal, 15 had physical complications, 15 had psychiatric comorbidity, and 15 had neurological complications such as epilepsy. VEP recordings were taken using an Evoked Potential Recorder (RMS EMG. EP MARK II) where the stimulus configuration consisted of transient pattern-reversal method in which a black and white checkerboard was generated full field. Results: Mean age of cases was 37.71 ± 11.49 years compared to 39.43 ± 10.67 years in controls (range 18–65 years). VEP abnormalities comprising of prolonged latencies (62.5%) with a statistically significant difference (P < 0.001) from the healthy controls was observed in cases of alcohol withdrawal syndrome. Predominant amplitude reduction with normal latency was obtained in 37.5% cases of withdrawal. Severe VEP abnormalities, i.e., both latency delay and amplitude reduction, were found in 75% patients with psychiatric comorbidity, 66.67% patients with neurological complications, i.e., epilepsy, and 33.34% patients with physical complications. An explicit finding of prominent interocular differences was a prominent feature present in 25% of patients with complications.

An investigative study on the impact of smoking on visual evoked response of healthy volunteers

Background: Cigarette smoking not only has numerous deleterious effects on respiratory and cardiovascular systems of the body but also poses a threat to damage the visual system and may lead to poor eyesight. Visual evoked potentials (VEPs) reflect electrical phenomena occurring during the visual processing so are widely used both in research and in clinical practice to elucidate the function of the visual system. Aim of Study: To explore the effect of smoking on the VEP response of healthy volunteers. Materials and Methods: VEP recordings were taken using an Evoked Potential Recorder (RMS EMG. EP MARK II) where the stimulus configuration consisted of transient pattern-reversal method, in which a black-and-white checkerboard was generated (full field) on a VEP monitor. Results: The mean age of thirty smokers was 46.70 ± 17.33 years compared to 47.25 ± 15.62 years in 60 controls (range 19–76 years). Predominant P100 latency delays in 60% of cases, of which 55.56% had markedly prolonged latencies. Both latency delay and amplitude reduction were seen in remaining 40% of cases, i.e., 12 of 30 smokers. Marked prolongation of latency with marked amplitude reduction was observed in 9 (75%) of these 12 cases and all belonging to the most chronic smokers. Conclusion: To the best of our knowledge, ours is one of the first studies to comment on implications of smoking on VEP. As VEP abnormalities obtained in cases of smokers having extreme chronicity were severe, substantial, and explicit, we propose that VEP could be a useful neurophysiologic tool to demonstrate the visual deficits due to smoking.

Atypical waveform morphology in schizophrenia-visual evoked potential as a promising endophenotype

Background: Electrophysiological research has provided measures of dysfunction of visual pathway in schizophrenia through the use of visual evoked potential (VEP) as the neurophysiologic tool. Objective: The main objective of this study is to examine the morphology and topography of VEP responses in schizophrenic patients and to explore the potentiality of VEP as an endophenotype. Materials and Methods: The study included 20 patients of schizophrenia who were recruited from the outpatient and inpatient department of psychiatry of a tertiary care rural hospital. The patients were assessed by tools such as Positive and Negative Symptoms Assessment Scale and Clinical Global Impression Scale for Severity. Transient Pattern Reversal VEP recordings were taken using an Evoked Potential Recorder (RMS EMG EP MARK II), and it was a cross-sectional study. Results: The mean age of patients was 45.95 ± 10.14 years in the range of 35–60 years. Qualitative analysis of VEP waveforms in people with schizophrenia was performed. Abnormal waveform morphology was observed in 14/20 (70%) of the study population and all of them were the chronic and severe cases. Six out of 15 (40%) showed lack of differentiation of the evoked complex so that the three waves (negative–positive-negative [NPN] complex) could not be identified. In 5 of 15 (33.33%) VEP records, a distinct altered waveform with extinguished second negative component of NPN complex was obtained. Conclusion: Qualitative morphometric findings of this study in terms of pattern-reversal VEP waveform abnormalities emerged as a tool to provide evidence of relationship for emerging as first potential biomarker for diagnosing schizophrenia.

Teratogenic effects of insulin: an experimental study on developing chick embryo.

Objective: The objective was to observe the effect of insulin on chick embryos with reference to their growth and developmental defects. Materials and Methods: An experimental study was performed to assess any abnormal growth pattern caused by insulin. For this, two batches of 100 fertilized eggs were utilized. One batch of 50 was used as a control group and other as an experimental group. Insulin (2 IU) was injected on day 2 of incubation. Chicken eggs were dissected out on day 19 of incubation and were carefully observed for any congenital abnormalities. The embryos thus dissected out were subjected to measurement of crown-rump length (CRL), changes in weight of egg, volume of embryos were compared in two groups. The embryos were also examined for any congenital anomalies. Results: No major malformations were observed. Decrease in weight and CRLs was lower in the experimental group as compared to their control counterparts. Values for volume of the embryo were similar in two groups. Conclusion: No obvious teratogenic effects are observed with insulin in the dose use for the study.