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  • Author or Editor: Robert M. Crowell x
  • By Author: DeGirolami, Umberto x
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Thomas W. Smith, Umberto DeGirolami and Robert M. Crowell

✓ The long-term toxic effects of ethyl 2-cyanoacrylate adhesive were evaluated histologically in 25 cats. Fresh medical- or commercial-grade adhesive was introduced transorbitally into the subarachnoid space in the vicinity of the right middle cerebral artery. Three sham-operated animals served as controls. The animals were sacrificed at intervals ranging from 2 days to 6 months. For both medical- and commercial-grade adhesive, neuropathological examination disclosed acute and chronic granulomatous inflammation of the meninges and evidence of severe vascular damage, including vessel wall necrosis, inflammation, thrombosis, and occasionally hemorrhage. Most animals showed cerebral infarcts of variable size in the territories of distribution of the basal arteries which were in contact with adhesive. The results of this study show that ethyl 2-cyanoacrylate is capable of producing severe arterial and parenchymal damage. The risk of its deleterious effects should be weighed against its potential benefits. Clinical experience would suggest that ethyl 2-cyanoacrylate can be used in difficult situations as long as care is taken to protect the brain and local blood vessels.

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Robert M. Crowell, Umberto DeGirolami and William H. Sweet

✓ The coincidence of arteriovenous malformation (AVM) and primary brain neoplasm is rare. We are reporting a case of oligodendroglioma within an arteriovenous malformation.

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Seiji Hayashi, Daniel G. Nehls, Charles F. Kieck, Juan Vielma, Umberto DeGirolami and Robert M. Crowell

✓ The authors performed a controlled study of induced hypertension therapy for treatment of experimental stroke in unanesthetized monkeys. Ten control and 10 treated animals were subjected to a 4-hour occlusion of the middle cerebral artery (MCA) by an implanted tourniquet. Neurological status and local cerebral blood flow (CBF) were monitored serially. Local CBF was determined by hydrogen clearance in and around the elevated 20% to 40% by intravenous infusion of phenylephrine hydrochloride. Neuropathological evaluation was performed after about 2 weeks.

A 4-hour occlusion of the MCA in control animals caused moderate stable neurological deficits, moderate stable decreases in local CBF, and medium-sized infarcts. With induced hypertension, five of 10 treated animals showed neurological improvement, and eight exhibited increased CBF in the ischemic zone. Average infarct size tended to be smaller in the treated group, although the difference did not reach statistical significance. Hemorrhagic infarcts were not observed. In four animals, phenylephrine caused cardiac dysrhythmias and hypotension which were reversed by appropriate measures. In this unanesthetized primate model of moderate experimental stroke, induced hypertension had beneficial effects on neurological status, local CBF, and infarct size without causing hemorrhagic infarction. Induced hypertension may be beneficial for some clinical cases of focal cerebral ischemia.

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Thomas H. Jones, Richard B. Morawetz, Robert M. Crowell, Frank W. Marcoux, Stuart J. FitzGibbon, Umberto DeGirolami and Robert G. Ojemann

✓ An awake-primate model has been developed which permits reversible middle cerebral artery (MCA) occlusion during physiological monitoring. This method eliminates the ischemia-modifying effects of anesthesia, and permits correlation of neurological function with cerebral blood flow (CBF) and neuropathology. The model was used to assess the brain's tolerance to focal cerebral ischemia. The MCA was occluded for 15 or 30 minutes, 2 to 3 hours, or permanently. Serial monitoring evaluated neurological function, local CBF (hydrogen clearance), and other physiological parameters (blood pressure, blood gases, and intracranial pressure). After 2 weeks, neuropathological evaluation identified infarcts and their relation to blood flow recording sites.

Middle cerebral artery occlusion usually caused substantial decreases in local CBF. Variable reduction in flow correlated directly with the variable severity of deficit. Release of occlusion at up to 3 hours led to clinical improvement. Pathological examination showed microscopic foci of infarction after 15 to 30 minutes of ischemia, moderate to large infarcts after 2 to 3 hours of ischemia, and in most cases large infarcts after permanent MCA occlusion. Local CBF appeared to define thresholds for paralysis and infarction. When local flow dropped below about 23 cc/100 gm/min, reversible paralysis occurred. When local flow fell below 10 to 12 cc/100 gm/min for 2 to 3 hours or below 17 to 18 cc/100 gm/min during permanent occlusion, irreversible local damage was observed.

These studies imply that some cases of acute hemiplegia, with blood flow in the paralysis range, might be improved by surgical revascularization. Studies of local CBF might help identify suitable cases for emergency revascularization.