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Biomedical subjects

S K Shankar

Publications and source records attributed to S K Shankar.

At least 73 records · Page 4Linked to original sources
PubMed1998

Identical twins with medulloblastoma occurring in infancy.

Familial cerebellar medulloblastomas occurred in monozygotic twin siblings during infancy, and they had a rapid downhill course. Both twins underwent surgery for the tumours. This was followed by chemotherapy in the second twin. Both died after a short time. The tumours were seen to arise from the cerebellum and both had almost identical histomorphological features. To the best of our knowledge, this is the second report of familial medulloblastoma in twin siblings. Our observation suggests an underlying genetic influence in the histogenesis of these tumours.

Cerebellar Neoplasms↗
PubMed1998

Neurocytoma/rhabdomyoma (myoneurocytoma) of the cerebellum.

An unusual case of cerebellar neurocytoma with rhabdomyomatous differentiation in a 6-year-old boy is reported. Immunocytochemical and ultrastructural features of the tumour were studied. Abortive synapse formation, the presence of clear vesicles and synaptophysin immunoreactivity of the tumour cells indicated its intermediate neuronal differentiation, while the presence of myoblasts and myotubes and immunolabelling by desmin confirmed the rhabdomyomatous differentiation. In addition, the mesenchymal cells variably expressed neurofilament protein and glial fibrillary acidic protein, suggesting inductive interaction between the neuroectodermal and ectomesenchymal elements and persistence of the pleuripotential nature of the cells along the rhombic area of the brain stem.

Cerebellar Neoplasms↗
PubMed1998

Cystic cavernous malformation of the cerebellopontine angle.

A 46 year old male presented with a cerebellopontine angle syndrome. CT scan and MRI revealed a cystic mass with a solid nodule in the cerebellopontine angle. At surgery, a vascular lesion was encountered which was totally excised in two stages. The histopathology was consistent with that of a cavernous malformation. Only four such cases have been reported so far in the English literature. The clinical and radiological features and the surgical management are discussed.

Cerebellar Diseases↗
PubMed1998

Sparganosis of brain and spinal cord: unusual tapeworm infestation (report of two cases).

Among the diseases due to cerebral parasitism, those caused by sparganum mansoni, the larval form of Spirometra mansoni, are very rare. We report two cases, one involving the frontoparietal area in a 38-year-old male and presenting as a mass lesion and another in a 10-year-old girl, presenting with paraparesis due to mid-thoracic compressive mass lesion. Pathological examination of the resected lesion revealed the characteristic plerocercoid larva, spargana, enclosed in acute inflammatory exudate, resembling an abscess. Postoperative recovery was good, suggesting that the best treatment for cerebral or spinal sparganosis mansoni is surgical excision. Serological tests for diagnosis were not carried out in these cases, since parasitic infection was not suspected. Although generally the role of immunodiagnosis is limited due to rarity of the condition, in endemic areas such tests may be useful in preoperative diagnosis.

Adult↗
PubMed1998

Reversible neuropathy in chronic renal failure.

Chronic renal failure is associated with distal symmetrical axonal neuropathy. We report a 50-year-old man who suffered from chronic renal failure due to benign enlargement of the prostate. He presented with fever and rapidly developing pure motor neuropathy. The nerve conduction velocity was slow and the F response delayed, suggestive of demyelinating neuropathy. A sural nerve biopsy specimen was also consistent with demyelination and axonal changes. This patient improved significantly following intermittent catheterization and a short course of norfloxacin. Renal failure may be associated with reversible motor neuropathy.

Axons↗
PubMed1998

Histopathological evaluation of inflammatory & hereditary demyelinating polyneuropathies.

In view of therapeutic implications and problems in clinical diagnosis, this study sought to evaluate and identify histopathological features of acquired inflammatory demyelinating neuropathies and hereditary demyelinating neuropathies. Sural nerve biopsies from 41 patients of demyelinating neuropathies, diagnosed on the basis of accepted clinical criteria, were studied using routine histological staining and special stains for myelin and axons. Chronic inflammatory neuropathies differed from the acute ones in having more endoneurial connective tissue, less of subperineurial oedema and presence of axonal sprouting and occasional onion bulb formation. Acquired neuropathies differed from hereditary neuropathies in having a more localized involvement, endoneurial oedema and variable inflammatory cell infiltration, while in hereditary neuropathies Schwann cell proliferation was diffuse and relatively uniform. The frequency and degree of nerve thickening was more in hereditary neuropathy. Evidence of inflammation was not universal, both in the acute and the chronic inflammatory demyelinating neuropathies. Histopathological examination is essential as the clinical and electrophysiological features alone may not offer definitive diagnosis.

Adult↗
PubMed1998

Relationship of rectal & hippocampal temperature profiles to seizure activity in rats prone & resistant to hot water induced epilepsy.

The present study evaluates the relationship of seizure proneness, to core body and brain temperature following hot water stimulation with water of 55 degrees C in freely ambulant rats. The rectal and hippocampal temperatures were recorded in 40 rats with bathing that included the head, while 10 other rats had similar thermal stimulation, but of the body alone. Bipolar stainless steel electrodes were stereotactically implanted into the dorsal hippocampal regions which served the dual purpose of recording the seizure discharges as well as regional brain temperature. It was observed that in the seizure prone (SP) rats, the mean rate of rise in rectal temperature was 1.5 degrees C/min, whereas in the seizure resistant (SR) animals it was 0.78 degree C/ min. However, there was no noticeable difference in the rate of rise in brain temperatures between the SP and SR groups, the rate of rise being 0.3 degree C/min. In the rats subjected to hot water bath over the body (excluding the head), there was no seizure activity. Further, there was no change in the brain temperature recorded in these rats, despite the rate of rise in rectal temperature being similar to that in the SP rats. These observations indicate that two thermoregulatory factors operate in seizure proneness-viz., a rapid rise in core body temperature; and a rise in local brain temperature. Both should coexist in order to elicit a hyperthermic seizure in rats.

Animals↗
PubMed1997

Co-existence of cerebral cysticercosis with Japanese encephalitis: a prognostic modulator.

In this study, we investigated the frequency of co-existence of cerebral cysticercosis (CC) in Japanese encephalitis (JE) cases with special emphasis on its role in predicting the final clinical outcome. Amongst the 163 confirmed cases of JE, 37.42% (61/163) had co-existent CC. This was confirmed by antibody detection in the CSF of 45 cases, CT scan of the brain in 6 cases and at autopsy in 3 cases. In 2 cases confirmation was possible by CT scan as well as at autopsy, in 4, CSF antibody levels and CT scan were suggestive of CC while in 1, CSF antibodies and autopsy were suggestive of CC The co-occurrence of Cysticercus cellulosae in the brain emerged as a prognosticator of poor outcome in JE cases (P < 0.03).

Adolescent↗
PubMed1997

Histopathological & immunohistochemical evaluation of ageing changes in normal human brain.

As age related changes in the brain have not been systematically studied in the Indian population though there is an impression that they are less frequent, we studied 52 brains collected at autopsy from individuals above the age of 60 yr. The incidence of senile plaques (SPs) and neurofibrillary tangles (NFTs) together were found to increase with age from 21 per cent in the seventh decade to 33 per cent in the eighth decade and 54 per cent in the ninth decade, the increasing incidence of NFTs being statistically significant. The SPs were found both in the hippocampus and frontal cortex while NFTs were seen only in the hippocampus in non-demented aged individuals. In contrast, in the three cases of Alzheimer's disease (symbol: see text) AD studied, the NFTs and SPs were found in high density in both hippocampus and frontal cortex. By immunohistochemistry, various morphological forms of SPs were found to have beta amyloid protein consistently, while ubiquitin and phosphorylated neurofilament occurred variably. More number of SPs could be labelled by amyloid immunostaining than by conventional silver stains. The NFTs contained ubiquitin and phosphorylated neurofilament protein as the antigenic components, both in AD and normal ageing. The incidence of age related changes and their antigenic character in the limited sample studied from south India appears to be comparable to findings from the West. Multicentric studies on a large sample derived from different ethnic groups in India are needed to further evaluate these features.

Aged↗
PubMed1997

Chediak-Higashi syndrome--a case report with ultrastructural and cytogenetic study.

We report the ultrastructural abnormalities of the leukocyte granules and the cytogenetic findings in a patient of Chediak-Higashi syndrome (CHS), who presented with cutaneous melanosis as the only clinical feature. The diagnosis of CHS was established by peripheral smear and bone marrow examination. Chediak-Higashi syndrome, a rare autosomal recessive disorder is characterized by enlarged abnormal organelles in leukocytes and other cells. An interesting aspect of our patient was the absence of recurrent infections or any other clinical stigmata. Ultrastructurally, the leukocytes and their precursors in the bone marrow showed characteristic homogenous and heterogenous giant inclusions of variable sizes and shapes. These represent the primary granules which enlarge to attain the giant abnormal size by fusion with other primary or secondary granules. Cytogenic study of the bone marrow cells showed monosomy of chromosomes 8 and 17 in 20 percent of the metaphases. Neither the gene nor the chromosomal abnormalities specific for CHS have been identified as yet and thus the significance of our cytogenetic finding is presently not clear.

Bone Marrow Cells↗
PubMed1997

Histological, histochemical and autoradiographic evidence of in vitro neurotoxic effects of the novel antitumor agent, 9-methoxy-N2-methylellipticinium acetate.

9-Methoxy-N2-methylellipticinium acetate (MMEA) exhibits selective cytotoxicity towards glial-derived human brain tumor cell lines comprising the U.S. National Cancer Institute preclinical drug screen. Neurotoxic potential of MMEA has been demonstrated in an in vitro model employing sagittal slices of rat brain. Histochemical staining of rat brain slices for lactate dehydrogenase (LDH) activity revealed decreased staining intensity following incubation with increasing concentrations of MMEA (0.1-100 microM). Cytological evaluation of paraffin sections stained with Cresyl Fast Violet revealed neuronal damage delineated by cytoplasmic vacuolation, and distention and fraying of the plasma membrane. No glial or vascular pathology could be discerned. Autoradiography, following exposure to 14C-MMEA, revealed distinct labelling of the large neurons of the brain stem, neurons in the thalamus and pyramidal neurons of the hippocampus, indicating neuronal uptake of the drug.

Animals↗
PubMed1996

Basal ganglionic angioleiomyoma.

A rare case of basal ganglionic angioleiomyoma in a 12-year-old girl is reported. She presented with features of raised intracranial tension, multifocal seizures, left hemidystonia and apraxia of eyelid closure. Cranial CT scan showed a large hypodense lesion with an enhancing mural nodule in the region of head of the caudate nucleus on the right side. The lesion was extending to the posterior limb of internal capsule postero-medially and to globus pallidus laterally. Another small, hyperdense, enhancing lesion was seen in the region of globus pallidus on the left side. The right basal ganglionic mass was excised through frontal craniotomy. Histopathological, Immunocytochemical and Ultrastructural examination of the right basal ganglionic mass showed features characteristic of angioleiomyoma. Following surgery the patient improved initially with respect to dystonia but worsened later on. Repeat cranial CT, 20 months after surgery, showed bilateral frontotemporal atrophy without any tumor recurrence while the lesion on the left side remained quiescent.

Angiomyoma↗