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Biomedical subjects

D O Quest

Publications and source records attributed to D O Quest.

53 records · Page 3Linked to original sources
PubMed1981

The effects of mannitol on blood viscosity.

To determine the effect of mannitol on blood viscosity, serial measurements were carried out on venous blood in patients undergoing craniotomies for intracranial aneurysms. Blood samples were drawn immediately prior to, and 30 minutes, 2, and 4 hours after administration of mannitol. Complete blood counts, serum osmolarities, and erythrocyte microsieving studies were also performed on each sample. Whole-blood viscosity decreased at 30 minutes and 2 hours, but not at 4 hours after mannitol administration. This decreased appeared at high shear rates only, where erythrocyte deformability is critical viscosity. This effect was independent of the hematocrit. Removal of mannitol from the suspension returned red cell deformability to preadministration values indicating that the increased erythrocyte deformability required the presence of mannitol and the relative hyperosmolarity induced by this agent. The reduced erythrocyte rigidity and subsequent decreased whole-blood viscosity should enhance tissue perfusion in the microcirculation.

Blood Viscosity↗
PubMed1980

Microsurgical anatomy of the pineal region.

The microsurgical anatomy of the pineal region was studied in 30 cadaver brains after the injection of a colored barium/gelatin mixture into the basilar artery and the straight sinus. The relationships of the pineal gland, vein of Galen, precentral cerebellar vein, internal cerebral veins, basal veins of Rosenthal, medial posterior choroidal arteries, quadrigeminal plate, pulvinar, splenium of the corpus callosum, and posterior 3rd ventricle were examined with the operating microscope and are described.

Cerebellum↗
PubMed1979

Artificial vision for the blind by electrical stimulation of the visual cortex.

Artificial vision for the blind may be feasible by interfacing a television camera with electronics stimulating the visual cortex. The status of a major collaborative effort involving the College of Physicians and Surgeons of Columbia University, the University of Utah, and the University of Western Ontario is reviewed. Results have been very encouraging, although much work remains to be done.

Blindness↗
PubMed1978

Period of risk for recurrence in medulloblastoma.

Ninety-nine patients with medulloblastoma who received surgery and radiotherapy, and had a statistically sufficient follow-up period were analyzed for factors influencing survival and the relevance of the "period of risk for recurrence" hypothesis. This postulate states that the period of risk for recurrence of a congenital tumor is equal to the age at presentation of illness plus 9 months' gestational time. The assumption is made that a tumor of embryonic origin will become manifest after a period of time determined by its inherent rate of growth and that tumor cells surviving treatment will multiply and present with recurrence in an equal period of time. Ten of 43 patients survived the period of risk, a presumed cure rate of 23%. None of these patients has subsequently developed evidence of tumor recurrence. Older patients at initial surgery had a somewhat greater survival rate for the first 5 years after treatment (10 of 26 older patients (38%) versus 15 of 54 younger patients (28%)), but by 10 years there was no appreciable difference in survival rates between those over 16 years of age and those younger. The beneficial effect of total neuraxis megavoltage radiotherapy is indicated by the improved 5-year survival rate from 9 of 41 patients (22%) to 16 of 39 patients (41%) with the newer techniques.

Adolescent↗
PubMedDate not supplied

Lack of association between carotid plaque hematoma and ischemic cerebral symptoms.

To investigate the association between carotid plaque hematoma and symptoms of cerebral ischemia a retrospective review of 200 consecutive carotid endarterectomies at the Neurological Institute of New York was carried out. Data analyzed included cerebral ischemic symptoms, angiographic findings, preoperative use of antithrombotic agents, and microscopic pathology of endarterectomy specimens. No association was found between ischemic symptoms ipsilateral to the endarterectomy and presence, size, or age of plaque hematomas. Plaque hematomas were less common among patients who took antithrombotic agents preoperatively than among those who did not. The presence of plaque hematoma was associated with angiographic carotid cross-sectional area stenosis of greater than 75%. Patients with stenosis of less than 75% were more likely than those with stenosis of greater than 75% to have ischemic symptoms ipsilateral to the endarterectomy, suggesting that criteria for surgical treatment of carotid atherosclerosis differ for those who are symptomatic vs. those who are asymptomatic. These results demonstrate the limitation of using a surgical series to extend causal inferences about the relation between plaque hematoma and cerebral ischemic symptoms to the general population of people with carotid atherosclerosis.

Aged↗
PubMedDate not supplied

The value of brain scanning in the management of strokes.

The usefulness of brain scanning in the diagnosis and management of strokes was evaluated in 313 serial cases. Of 38 patients with transient ischemic attacks (TIAs), only one had a positive test. The optimal time for scanning completed strokes was between seven and 14 days after onset. The pattern of uptake was characteristic of a vascular lesion in 76.8%. When uptake was indistinguishable from tumor, follow-up scans were useful. Patients with negative scans in the second week have a significantly better prognosis than the ones with a positive study. Cerebral angiography and brain scan correlated well in 56 patients who had both tests performed. The postmortem findings in 12 cases again emphasize the importance of the correct timing of the study, and the fact that a brain scan does not usually demonstrate lesions smaller than 2 cm in diameter. It is concluded that the brain scan represents a useful tool in the diagnosis of strokes and helps in predicting the degree of recovery following a vascular insult.

Aged↗
PubMedDate not supplied

Meningiomas: an update.

The author has reviewed the topic of meningiomas. He has discussed especially the clinical presentations of such tumors according to location and has summarized their pathological nature and biological behavior.

Adult↗