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Biomedical subjects

S Venkatesh

Publications and source records attributed to S Venkatesh.

At least 55 records · Page 3Linked to original sources
PubMed1995

Alteration of pulse configuration affects the pain response during diode laser photocoagulation.

BACKGROUND AND OBJECTIVE: The shape of the treatment pulse of the diode laser (810 nm) can be easily altered electronically in contrast to ion laser photocoagulators. We investigated whether changes in laser pulse shape influenced the subjective pain responses in patients undergoing retinal photocoagulation when only topical anesthesia was used. STUDY DESIGN/MATERIALS AND METHODS: Twenty consecutive patients required peripheral retinal photocoagulation for proliferative diabetic retinopathy or extensive retinal breaks. Three diode pulse waveforms including a square wave, shaped-wave, and an envelope of micropulses were compared to one another. Power was adjusted so that each waveform delivered the same total energy. The patients subjectively ranked the intensity of any pain they experienced for each group of lesions. Responses were compared to one another using an analysis of variance. RESULTS: 40% of patients found the standard square wave pulse to be significantly more painful (P < 0.05) than the shaped pulse mode and 30% found the square wave significantly more painful (P < 0.05) than the micropulse mode. CONCLUSION: Modification of the laser pulse waveform may ameliorate pain induced by diode laser photocoagulation of the retinal periphery.

Analysis of Variance↗
PubMed1995

Stimulation distal to the lesion in patients with carpal tunnel syndrome.

In patients with carpal tunnel syndrome, low action potential amplitude after stimulation at the wrist (proximal to the lesion) is due to either demyelination or axonal degeneration. Demyelination can be distinguished from axonal degeneration by the presence of amplitude drop across the lesion. Amplitude drop is determined by comparison of action potential amplitude evoked by stimulation at the palm (distal to the lesion) with that of the wrist. Of 59 consecutive CTS patient hands, 36 (61%) showed significant reduction in CMAP and/or antidromic SNAP amplitudes at the wrist compared to the palm, indicating the presence of focal demyelination resulting in conduction block vs. pathologic dispersion with phase cancellation. Moreover, the smaller the wrist-evoked action potential amplitude, the greater the amplitude drop across the lesion. We conclude that in patients with CTS, as in other entrapment neuropathies, stimulation both proximal and distal to the lesion provides important pathophysiological information about the median nerve lesion.

Action Potentials↗
PubMed1995

Electromyography: do the diagnostic ends justify the means?

BACKGROUND: Physicians are sometimes reluctant to refer patients for electrodiagnostic studies (electromyography with nerve conduction studies [EMG/NCS]) believing the test is too painful and of little benefit. METHODS: We performed two separate surveys on 126 and 100 consecutive patients referred to our laboratory to determine if EMG/NCS was beneficial to the referring physician and to compare the level of anxiety experienced by patients before the study with the pain actually experienced during the study. RESULTS: The electrodiagnosis was discordant from the referring diagnosis in 39% of the patients with an abnormal EMG/NCS. Pretest anxiety levels were low in 59% of the patients, medium in 27%, and high in 14%. After the tests, 82% of the patients said that the test was not as bad as expected, and was generally only mildly painful. Ninety-three responded that they would have the test performed again. CONCLUSIONS: EMG/NCS often suggest alternative diagnoses, and the actual pain experienced during an EMG/NCS study is significantly less than expected.

Adult↗
PubMed1995

Acute aphasia complicating typhoid fever in an adult.

Motor aphasia complicating bacteriologically confirmed typhoid fever in a 20-year-old adult female is presented. Neither the cause of death nor the aetiology of this isolated neurological deficit could be determined from detailed post-mortem examination. An immune related mechanism is suggested based on the temporal characteristics of this complication and CSF abnormalities.

Acute Disease↗
PubMed1994

Submaximal stimuli activate different nerve fiber populations at different sites.

Theoretically, the largest and fastest nerve fibers are preferentially stimulated with submaximal stimuli. However, it is also well known that intraneural fascicular topography changes substantially along a proximal to distal axis. Because of this change in fascicular topography, we hypothesized the percutaneous submaximal stimuli applied to a nerve at different locations would stimulate different subpopulations of large fibers. We performed a series of collision studies by stimulating the ulnar nerve submaximally at proximal and distal sites at varying levels of stimulation intensity from motor threshold to supramaximal stimulation. The results suggest that variation in intraneural topography at different sites allows different large diameter nerve fiber subpopulations to be activated at submaximal stimuli, and emphasizes the importance of supramaximal stimulation to determine a valid conduction velocity.

Action Potentials↗
PubMed1994

Neuroaxonal dystrophy at birth with hypertonicity and basal ganglia mineralization.

A full-term male infant exhibited rigidity of all extremities with hyperreflexia beginning soon after birth and lasting until his death at age 6 months. Head circumference remained at the 25th to 50th percentile. Distinct sleep-wake cycles and responsiveness to visual, auditory, and tactile stimuli developed. Metabolic studies, skin biopsy, electroencephalography, and electromyography produced normal results. Head computed tomographic and magnetic resonance imaging scans revealed mineralization of the basal ganglia and thalamus. Muscle and nerve biopsy results were consistent with axonal dystrophy. Autopsy showed widespread neuronal loss, with reactive gliosis, marked in the globus pallidus and brainstem reticulate core; spheroids in globus pallidus, nucleus cuneatus, and upper cervical cord; and mineralized neurons in the inner division of globus pallidus and thalamus. Neonatal hypertonia, rapid progression, and mineralization of the basal ganglia are unusual features of neuroaxonal dystrophy exhibited in this case.

Autopsy↗
PubMed1993

Alterations of auditory middle latency evoked potentials during yogic consciously regulated breathing and attentive state of mind.

Middle latency auditory-evoked potentials (AEP-MLRs) of 10 healthy male subjects in the age range of 21-33 years, were assessed to determine whether yogic pranayamic practice would cause changes in them. The pranayama type assessed here is an exercise of consciously-controlled rhythmic breathing involving timed breath-holding in each cycle of breathing, while the subject holds utmost attention and experiences the touch of inhaled air in the nasal passage. The results revealed that the Na-wave amplitude increased and latency decreased during the period of pranayamic practice, whereas the Pa-wave was not significantly altered. The change is interpreted as an indication of a generalized alteration cause in information processing at the primary thalamo-cortical level during the concentrated mental exercise of inducing modifications in neural mechanisms regulating a different functional system (respiratory). Further researches are required to understand the operational significances of such changes.

Acoustic Stimulation↗
PubMed1993

Cystic fibrosis in one family.

Two patients with cystic fibrosis from the same family are reported. Both patients had features of chronic respiratory disease with evidence of pancreatic and other systemic manifestations. To our knowledge this is the first report from our country of cystic fibrosis multiplex cases occurring in the same family.

Adolescent↗
PubMed1992

Thyrotoxic periodic paralysis in a Jamaican male patient.

A case of thyrotoxic periodic paralysis occurring in a Black Jamaican male patient is described. Diagnosis is based on history and confirmed by evaluation of serum electrolyte during attacks and thyroid function studies. The pathophysiology, associations, therapy and prognosis are discussed. It is important that clinicians recognise the condition as all forms of periodic paralysis are amenable to treatment, and progressive weakness can be prevented or even reversed.

Adult↗
PubMed1991

Accumulation of phosphatidic acid mass and increased de novo synthesis of glycerolipids in platelet-activating-factor-activated human neutrophils.

Incubation of human neutrophils with 100 nM-platelet-activating factor (PAF) but without cytochalasin B resulted in a rapid (5 s) accumulation (1.6-fold) of phosphatidic acid (PtdOH) mass. The increased PtdOH mass reached a maximum (2.8-fold) at 1 min and remained elevated (1.7-fold) at 10 min. No methylamine-stable lyso-PtdOH was detectable in the total lipid extract from control or from PAF-activated cells, suggesting that diacyl-PtdOH was the predominant species. In PAF-activated cells, changes in 1,2-diacylglycerol (DG) mass were not detectable at 5 or 15 s. Increased DG mass (1.7-fold) was detected between 30 s and 2 min, but then it declined to basal levels by 10 min. PAF enhanced [3H]glycerol incorporation into PtdOH and DG by 2- and 3-fold respectively during 1-10 min incubations. PAF also increased the radioactivity but not the mass of phosphatidylinositol and of choline glycerophospholipid by 8-fold and 4-fold respectively at 10 min. In addition, PAF-activated cells showed increased (2-fold) glycerol incorporation into triacylglycerol. These results demonstrate that PAF enhances rapid accumulation of diacyl-PtdOH mass, and that increased de novo synthesis may contribute to PtdOH mass accumulation.

Diacylglycerol Kinase↗
PubMed1990

Islet cell carcinoma of the pancreas. A study of 98 patients.

In 98 patients with histologically proved pancreatic islet cell carcinoma who were studied between 1950 and 1987, 55 had functioning tumors and 43 had nonfunctioning tumors. Both patient groups were compared in regard to age at presentation, metastases, and survival. Mean age at diagnosis was 51.1 years for the 55 men and 47 years for the 43 women. At diagnosis, 51 of the patients had regional disease and 47 had distant metastases. When matched for age, sex, and extent of disease, survival did not differ significantly in cases of functioning and nonfunctioning tumors. The patients' ages and the extent of disease at presentation were the most significant factors in prognosis and survival.

Adenoma, Islet Cell↗
PubMed1990

Brain metastases in patients with well-differentiated thyroid carcinoma: study of 11 cases.

Eleven patients, three males and eight females, developed brain metastases from well-differentiated thyroid carcinoma 1 to 20 years after their original diagnosis. Two had brain metastases only and nine had metastases to the lungs and bones as well. Most patients died within a year of diagnosis of brain metastases. We conclude that brain metastasis from thyroid carcinoma carries a poor prognosis and that newer modalities of therapy may be needed.

Adolescent↗
PubMed1989

Adrenal cortical carcinoma.

The records of 110 patients (58 females and 52 males) with histologically proven adrenal cortical carcinoma were studied. Fifty-six of 110 (50.9%) patients had abdominal symptoms and 33 (30.0%) had a palpable abdominal mass. Surgery for localized and regional disease was associated with a disease-free survival time of at least 2 years in 28 of the 50 (56%) patients. Abdominal radiotherapy, systemic chemotherapy, and 1,1 dichloro-2 (O-chlorophenyl)-2 (P-chlorophenyl) ethane (OPDDD) were effective in three of 19 (15.8%) patients, three of 31 (9.7%) patients, and 21 of 72 (29.2%) patients, respectively. Combined radiotherapy and OPDDD did not confer any additional benefit over OPDDD alone. Six of seven patients who received OPDDD as adjuvant treatment are still alive at 1 to 4 years. Distant metastases occurred most commonly in the lungs, liver, peritoneum, lymph nodes, and bones. Only 23% of the patients survived 5 years or more. We conclude that early diagnosis and complete surgical excision offer the best prospects for long-term survival and that the efficacy of adjuvant OPDDD needs to be evaluated further.

Adolescent↗