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T Sharma

Publications and source records attributed to T Sharma.

At least 73 records · Page 4Linked to original sources
PubMed1999

Hippocampal volume reduction in schizophrenia: effects of genetic risk and pregnancy and birth complications.

BACKGROUND: Hippocampal volume reduction has been repeatedly demonstrated in schizophrenia. The relative contribution of genetic and environmental factors to this is unclear. METHODS: To address this question, we compared volumetric measurements of the left and right hippocampus, obtained using stereological methods from brain MRI scans, from two groups of patients with schizophrenia as well as healthy controls (n = 26). Patients (n = 27) in the first group, had no family history of schizophrenia and had experienced severe pregnancy and birth complications (PBCs). The second group comprised of patients (n = 21) without a history of severe PBCs from families multiply affected with schizophrenia. RESULTS: Reduction of the left hippocampal volume was associated with the diagnosis of schizophrenia but was present only in patients with a history of severe PBCs; in this group the smaller hippocampal volume, the earlier the onset of psychosis. CONCLUSIONS: Our findings suggest that environmental factors, in this case severe PBCs, make a significant contribution to hippocampal abnormalities in schizophrenia.

Adult↗
PubMed1999

Attenuated frontal activation in schizophrenia may be task dependent.

UNLABELLED: Functional magnetic resonance imaging was used to examine the neural correlates of two linguistic tasks in schizophrenia. METHOD: Five dextral male schizophrenic patients and five volunteers matched for demographic variables and task performance participated. Echoplanar images were acquired over 5 min at 1.5 T while subjects performed two paced, covert tasks; (1) verbal fluency: silent generation of words beginning with an aurally presented cue letter, contrasted with silent repetition of the aurally presented word 'rest'; (2) semantic decision: deciding whether a visually presented cue word was 'living or non-living' and silently articulating the response, contrasted with rest. Both tasks entailed language processing; only verbal fluency requires the intrinsic generation of verbal material. Between-group differences in the mean power of experimental response to the semantic decision task were identified by a one-way analysis of covariance (ANCOVA), with a measure of stimulus-correlated motion as a covariate. Voxels demonstrating a significant interaction between task and group were identified using a two-way ANCOVA. RESULTS: In controls, both tasks were associated with activation of prefrontal cortex. In patients with schizophrenia there was a significantly reduced power of response in several prefrontal regions during verbal fluency relative to controls, a difference that was not evident for the semantic decision task. There was a significant group x task interaction in the left inferior frontal gyrus, left dorsolateral prefrontal cortex and the supplementary motor area at voxel and regional levels of analysis. CONCLUSIONS: Attenuation of frontal activation during cognitive task performance in schizophrenia does not represent a fixed deficit in frontal function, but may depend on the specific cognitive demands of the experimental task employed.

Adult↗
PubMed1999

Mapping of grey matter changes in schizophrenia.

Studies of brain changes in schizophrenia have suggested that the disorder is associated with reductions in both global and regional grey matter. In this study, we used structural neuroimaging to differentiate between these two types of change and to examine regional grey matter throughout the whole brain. Grey matter from magnetic resonance images was segmented and transformed into stereotactic space, and patients with schizophrenia and controls were compared with respect to regional grey matter (after compensating for global grey matter differences). In two preliminary analyses to test our methodology, we demonstrated that: (1) in the transformed grey matter maps, voxel values at the location of the caudate nuclei were correlated with region-of-interest measurements of caudate area in native image space, and (2) the technique detected regional grey matter changes resulting from artificial lesions created in the native images. We then used a factorial design to examine data from two studies, comprising a total of 42 schizophrenics and 52 controls. Analysis of the main effect of schizophrenia on regional grey matter revealed significant reductions in (a) the right temporal pole, insula and amygdala, (b) the left temporal pole, insula and dorsolateral prefrontal cortex.

Adult↗
PubMed1999

Supra-regional brain systems and the neuropathology of schizophrenia.

At what levels of brain organization might pathological change in schizophrenia be anatomically expressed: global, regional or supraregional? We hypothesised that brain structure reflects a set of supra-regional anatomical systems with common developmental influences. We conducted an exploratory analysis to identify supraregional brain systems and to investigate whether abnormal brain architecture in schizophrenia is manifested within one or more of these systems. Magnetic resonance (MR) images were acquired from 27 patients with schizophrenia and 37 control subjects. After segmentation and registration of each individual MRI dataset in the standard space of Talairach and Tournoux, grey matter and ventricular-cerebrospinal fluid (CSF) maps were automatically parcellated into 104 regions. We used principal components analysis of the multiple regional grey matter and ventricular-CSF measurements, on all 64 subjects, to extract the five main normative supra-regional systems. The first two of these components represented global variation in grey matter and ventricular-CSF regional measures. We interpreted the other three components as representing supra-regional systems comprising: a frontal-parietal system, a frontal-temporal system and a frontal-basal ganglia system. Schizophrenic group mean scores on the first component (global grey matter-ventricular contrast) and fourth component (frontal-temporal system) were significantly reduced compared to controls. These results suggest that pathological change in schizophrenia may be expressed at two mutually independent levels of anatomical organization: global change in a grey matter/ventricular system and supra-regional change in a frontal-temporal system.

Adult↗
PubMed1999

Vitreoschisis in Eales' disease: pathogenic role and significance in surgery.

PURPOSE: To report the surgical anatomy of vitreoretinal adhesions as observed intraoperatively in patients undergoing vitreous surgery for complications of Eales' disease. METHODS: Eighteen consecutive male patients (18 eyes) undergoing vitrectomy for Eales' disease were studied prospectively. Intraoperative diagnosis was vitreous hemorrhage (VH) in nine cases, traction retinal detachment (TRD) in four, VH and TRD in three, and combined traction-rhegmatogenous retinal detachment in two. Epiretinal membranes (ERMs) obtained during surgery were studied using light microscopy and immunohistochemistry. RESULTS: An incomplete posterior vitreous detachment was observed in all eyes. Multifocal vitreoretinal adhesions were evident in 83.3% of eyes. The proliferation was fibrovascular in 10 eyes and fibrous in eight. A radial traction fold extending from optic disk to periphery was observed in three eyes. A double-layered membrane, probably the result of vitreoschisis, caused tangential traction. ERMs consisted principally of type II collagen and the cellular element was predominantly composed of lymphocytes, glial cells, and macrophage-like cells (probably hyalocytes). CONCLUSIONS: Fibrous and fibrovascular proliferations have multiple areas of adhesions to the posterior vitreous cortex. The presence of type II collagen in the ERM indicates a possible vitreous collagen component to the double-layered membranes (vitreoschisis). Recognition of the double-layered membranes aids in relief of traction during surgery by delamination.

Adult↗
PubMed1999

Normalization of information processing deficits in schizophrenia with clozapine.

OBJECTIVE: The authors tested the hypothesis that the use of an atypical drug, clozapine, for patients with schizophrenia is related to less impairment in information processing deficits (assessed by prepulse inhibition of the startle response) than is the use of typical antipsychotics. METHOD: Two groups of schizophrenic patients--receiving either clozapine or a range of typical antipsychotics--were tested for prepulse inhibition (a reduction in response to a starting stimulus, if preceded briefly by a weak, nonstartling stimulus; measured at prepulse-to-pulse intervals of 30 msec, 60 msec, and 120 msec) of the acoustic startle response and compared with a group of healthy volunteers. RESULTS: Patients receiving typical antipsychotics showed less prepulse inhibition with 30-msec and 60-msec prepulse trials than did comparison subjects. Clozapine-treated patients showed normal levels of prepulse inhibition. CONCLUSIONS: Clozapine is superior to typical antipsychotics in normalizing prepulse inhibition, presumably because of its pharmacological effects on prefrontal regions of the brain or its effects on a broader range of neuroreceptors.

Acoustic Stimulation↗
PubMed1999

No evidence for left superior temporal dysfunction in asymptomatic schizophrenia and bipolar disorder. PET study of verbal fluency.

BACKGROUND: Positron emission tomography (PET) studies have revealed functional left superior temporal gyrus (STG) abnormalities in symptomatic schizophrenia during word generation. AIMS: To discover if this dysfunction is present in asymptomatic schizophrenia. To determine whether, without concurrent symptomatology, schizophrenia and bipolar affective disorder (BPD) are distinguishable by differing regional cerebral blood flow (rCBF) patterns during word generation. METHOD: A PET verbal fluency protocol was applied to six patients with BPD in remission and six patients with asymptomatic schizophrenia. Analysis included 10 control subjects from a contemporaneous study. RESULTS: All groups showed relative reduction of rCBF in both superior temporal cortices. There were no quantitative differences in any group comparison. All groups exhibited negative covariation between rCBF in left prefrontal and right (but not left) temporal regions. CONCLUSIONS: Abnormal patterns of left STG function cannot be regarded as a trait marker for schizophrenia. Functional abnormalities may reflect aspects of mental state.

Adult↗
PubMed1999

A rural population based case-control study of senile cataract in India.

PURPOSE: Senile cataract contributes to 75% of blindness in India and there is a growing backlog of cataract cases needing surgery. The present study seeks clues to the etiology of senile cataract, so that strategies to prevent or even delay cataract formation could be planned. METHODS: Using a community based case-control design, 258 cases & 308 controls from one centre and 301 cases & 591 controls from another were studied. The subjects were from rural areas and were aged 40-60 years. Logistic regression analysis technique was employed to study the associations between senile cataract and various variables. RESULTS: Systolic blood pressure, duration of exposure to sunlight per day were associated with senile cataract in both the centres (OR = 1.4 & 1.5 for systolic BP and 1.6 & 1.4 for exposure to sunlight). Utilization of rice gruel (OR = 0.5), duration of exposure to fire & dust per day (OR = 1.8), family history of cataract (OR = 5.0), use of cheap cooking fuels (OR = 1.8), increased height (OR = 0.7) and increased number of hours of work per day (OR = 0.7) were other variables that showed significant association in either of the centres. CONCLUSION: Senile cataract appears to have a multi factorial etiology. Though the study provided some clues to the etiology of senile cataract, further studies are needed to know the specific role of these factors in the causation of cataract, so that any preventive or control measures could be initiated in the community. Till such time, we have to fall back on the available surgical approach in control of senile cataract.

Adult↗
PubMed1999

Functional MR imaging of confounded hypofrontality.

Comparatively reduced blood flow to frontal brain regions in patients with schizophrenia (hypofrontality) has been frequently observed in the last 25 years. However, there is an inconstant quality to hypofrontality, suggesting either confounded observation of a static (trait-like) abnormality, or that it is a genuinely dynamic (state-like) phenomenon. Possible confounds in functional magnetic resonance imaging (fMRI) studies of hypofrontality are classified. Methods for assessment and correction of stimulus correlated motion (an extracerebral confound) are reviewed in the context of fMRI data acquired from five schizophrenic patients and five comparison subjects during performance of a verbal fluency task. Factorial analysis of these and other data, acquired from the same subjects during a semantic decision task, is used to exclude a number of possible intracerebral confounds. By analogy to the historical controversy concerning the appearance of the planet Saturn viewed through early telescopes, understanding the inconstancy of hypofrontality in schizophrenia is likely to progress more by theoretically driven experiments that exploit the repeatability of fMRI than by further technological development alone.

Analysis of Variance↗
PubMed1999

pH-adjusted periocular anaesthesia for primary vitreoretinal surgery.

PURPOSE: To evaluate the efficacy of pH-adjusted bupivacaine in conjunction with medial orbital periconal block (periocular anaesthesia). METHODS: Sixty consecutive patients undergoing primary vitreoretinal surgery were enrolled prospectively. RESULTS: Adequate anaesthesia and akinesia with no intraoperative supplementation was achieved in 53 eyes (88.3%). Factors influencing intraoperative supplementation were combined vitrectomy with scleral buckling (p = 0.005) and duration of surgery of more than 2 hours (p = 0.001). No ocular or systemic complication resulted. CONCLUSION: pH-adjusted periocular anaesthesia is safe and effective in patients undergoing primary vitreoretinal surgery.

Adult↗
PubMed1999

Methods for diagnosis and treatment of stimulus-correlated motion in generic brain activation studies using fMRI.

Movement-related effects in realigned fMRI timeseries can be corrected by regression on linear functions of estimated positional displacements of an individual subject's head during image acquisition. However, this entails biased (under)estimation of the experimental effect whenever subject motion is not independent of the experimental input function. Methods for diagnosing such stimulus-correlated motion (SCM) are illustrated by application to fMRI data acquired from 5 schizophrenics and 5 normal controls during periodic performance of a verbal fluency task. The schizophrenic group data were more severely affected by SCM than the control group data. Analysis of covariance (ANCOVA) was used, with a voxelwise measure of SCM as a covariate, to estimate between-group differences in power of periodic signal change while controlling for variability in SCM across groups. Failure to control for SCM in this way substantially exaggerated the number of voxels, apparently demonstrating a between-group difference in task response.

Adult↗
PubMed1998

Primary vitrectomy for rhegmatogenous retinal detachment associated with choroidal detachment.

OBJECTIVE: This study aimed to report the success rate of primary vitrectomy, scleral buckling, and oral steroids in eyes with combined rhegmatogenous retinal detachment (RRD) and choroidal detachment (CD) and to compare these results with those reported in the literature for similar cases managed by scleral buckling alone. DESIGN: Consecutive case series. PARTICIPANTS: Twenty-one eyes of 21 consecutive patients with primary RRD associated with CD were examined. INTERVENTION: All patients were treated with systemic corticosteroids before surgery. Pars plana vitrectomy with scleral buckling or encircling or both were performed. MAIN OUTCOME MEASURES: Retinal reattachment rate and resolution of choroidal detachment were measured. RESULTS: At mean follow-up of 11.4 months, retinal reattachment was attained in 19 eyes (90.5%) compared to less than 53% reported in the literature for scleral buckling alone. With preoperative oral steroids, choroidal detachment regressed completely in 13 eyes (61.9%). In the remaining eyes with persistent choroidal detachment, suprachoroidal fluid was drained during vitrectomy. CONCLUSION: Aggressive treatment with oral steroids followed by pars plana vitrectomy and scleral buckling or encircling is recommended instead of scleral buckling alone in the management of combined primary rhegmatogenous retinal detachment and choroidal detachment.

Administration, Oral↗
PubMed1998

Surgical management of retinal detachments related to coloboma of the choroid.

OBJECTIVE: This study aimed to develop a rationale for the management of retinal detachments related to choroidal coloboma and to study the outcome of their management. DESIGN: The study design was a retrospective study. PARTICIPANTS: A total of 85 eyes of 81 patients with retinal detachments related to coloboma of the choroid participated. INTERVENTION: All eyes underwent pars plana vitrectomy with internal tamponade using silicone oil (80 eyes) or perfluropropane gas (5 eyes). Behavior of the retina on fluid-air exchange was used to guide the further steps of surgery. Endolaser was performed along the coloboma border. Silicone oil was removed in 80% of eyes. The main outcome measures were retinal reattachment and visual recovery. RESULTS: Recurrent retinal detachment occurred in 16.3% of silicone oil-filled eyes and 60% of gas-filled eyes. After silicone oil removal, 15.6% of eyes had recurrent retinal detachment. After a mean follow-up of 13.4 months, 81.2% of eyes had attached retina and 69.4% recovered equal to or better than 10/200 visual acuity. CONCLUSION: Retinal detachment secondary to coloboma of choroid is treated best by pars plana vitrectomy along with silicone oil tamponade. Gas tamponade has limited indications. Clinical evaluation of the extent of retinal detachment within the colobomatous area and the behavior of the retina on fluid-air exchange help the authors understand the pathogenesis of the retinal detachment and plan a rational therapy.

Adolescent↗
PubMed1998

Long term visual results of vitrectomy for Eales disease complications.

BACKGROUND AND OBJECTIVES: Complications of Eales disease can cause visual loss. Long term visual prognosis following vitrectomy for Eales disease complications has been studied. PATIENTS AND METHODS: Retrospective analysis of 64 eyes of 57 patients who underwent vitrectomy for Eales disease complications with a minimum follow-up of 60 months. RESULTS: 62.4% eyes at 2 months and 71.8% at 60 months had 6/60 or better visual acuity. Visual acuities for individual cases were quite stable at the 60 month follow up with 50 eyes (78.5%) either maintaining or improving upon their 2 month post operative visual acuity. CONCLUSION: Visual acuity improves after vitrectomy in majority of patients with Eales disease complications and remains stable on long term follow-up.

Adolescent↗
PubMed1998

Intraoperative mitomycin C and the corneal endothelium.

PURPOSE: Mitomycin-C (MMC) is a useful adjunct to high risk glaucoma surgery. No clinical data regarding the deleterious effect of mitomycin-C on the corneal endothelial cells are available. METHODS: Thirty eyes of 28 adult patients with high risk glaucomas were randomized to three groups. Group-I underwent a trabeculectomy alone, Group II, trabeculectomy with intraoperative 0.2mg/ml MMC and Group III, trabeculectomy with intraoperative 0.4mg/ml MMC. Preoperative and 3-month postoperative corneal endothelial cell counts were analysed. RESULTS: The percentage cell loss in Group I was 3.73+/-2.73%, in Group II 13.90+/-4.69% and in Group III 14.52+/-7.8%. Statistical analysis revealed a significant difference in cell loss between Group I and Group II and Group I and Group III, but not between Group II and Group III. CONCLUSION: There is a significant loss of corneal endothelial cells three months after trabeculectomy with adjunctive MMC.

Adult↗