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Biomedical subjects

S J Peerless

Publications and source records attributed to S J Peerless.

70 records · Page 4Linked to original sources
PubMed1967

Shear injuries of the brain.

A blow to the head will impart rotational velocity to the brain and, depending on its magnitude, will produce effects ranging from concussion to profound neurological dysfunction. Resultant shear strains distort and rupture axons, blood vessels and major fibre tracts. Thirty-seven patients with head injury that was not complicated by significant hemorrhage or superficial laceration of the brain had coma or severe dementia, spastic quadriparesis, incontinence and autonomic dysfunction. These patients survived 24 hours to 243 days. Gross pathological examination revealed little, but there was microscopic evidence of axonal and small vessel injury in all; this was localized to the basal and midsagittal areas of the diencephalon and mesencephalon, particularly in those less severely injured. Such changes represent the basic pathology of all head injury. Data from this study suggest that concussion depends upon varying degrees of damage to the axon as well as the neuron. The current definition of concussion-immediate loss of consciousness with rapid and complete recovery of cerebral function-should not exclude the fact that a small number of neurons may have been permanently disconnected or have perished.

Axons↗
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Protective effect of Fluosol-DA in acute cerebral ischemia.

Fluosol-DA (Perfluorochemical Blood Substitutes) are small particle fluorocarbons suspended in an emulsion and have a high propensity for carrying oxygen and carbon dioxide. Fluosol-DA was investigated for the modification of acute focal cerebral ischemia and compared to mannitol. A total of 36 adult cats were divided into 3 groups and had transorbital microtourniquet ligation of the middle cerebral artery (MCA). Control animals were given intravenous isotonic saline. Animals in the experimental groups were treated with either intravenous Fluosol-DA or mannitol. All animals were nursed in an oxygen chamber and 4 cats from each group were sacrificed at 1, 3 and 6 hours after MCA occlusion. The results of macroscopic and histological examination of the brain suggested Fluosol-DA had a definite protective effect on acute focal cerebral ischemia which was in keeping with the observed neurological outcome. It is suggested that Fluosol-DA may support flow in the microcirculation and that the small particles of Fluosol-DA may be able to reach the area of ischemia via collaterals by decreasing blood viscosity, preventing narrowing of the arteriolar and capillary lumen and increasing the cerebral blood flow.

Animals↗
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Angiographic study of vasospasm following subarachnoid hemorrhage in monkeys.

A model for producing chronic cerebral vasospasm in monkeys by injecting autologous blood into the basal cistern is described. Spasm/narrowing was observed by angiography one hour after SAH in 8 out of 10 monkeys and in 5 of these 8, spasm was observed both one and two weeks later. No narrowing of the vessels was observed in the control cases. In monkeys that showed spasm one week after SAH, narrowing of the extracranial vertebral arteries was also observed. Repeated injections of blood at intervals of one and two weeks caused intensification of spasm in the intracranial portion of vertebral arteries and the basilar arteries. It is suggested that cerebral vasospasm following SAH may in part be mediated by a central control mechanism acting through the sympathetic nervous system in that extracranial vessels remote from direct contact with blood showed reactive narrowing.

Animals↗
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The effect of Fluosol-DA on oxygen availability in focal cerebral ischemia.

The effects of Fluosol-DA 35% (15 ml/Kg, IV) on cortical oxygen availability (O2a), a relative measurement of cortical oxygen tension, were examined in 16 cats subjected to temporary middle cerebral artery (MCA) occlusion. The cats were divided equally into control and treatment groups and half of each group underwent MCA occlusion at room air ventilation and the other half at 100% O2 ventilation. Prior to occlusion, Fluosol had no effect on arterial PO2 or cortical O2a at normoxia, however, there was a significant increase in both arterial PO2 and O2a following 100% O2 ventilation (pre vs post Fluosol). In an additional 5 cats, Fluosol resulted in a transient decrease in blood oxygen content due to hemodilution. Concurrent to this decrease, cerebral blood flow increased substantially resulting in a net increase in oxygen delivery. Within ipsilateral hemispheres, MCA occlusion resulted in decreased O2a to levels below the pre-occlusion normoxic values in all animals except those treated with Fluosol and ventilated with 100% O2. During reperfusion, O2a immediately recovered to hyperoxic levels in the Fluosol 100% O2 animals, whereas in the other three groups, O2a returned more gradually towards the pre-occlusion value. Since neither 100% O2 alone nor Fluosol plus room air ventilation significantly improved O2a in the ischemic cortex, we conclude that increased delivery of plasma plus Fluosol bound oxygen was responsible for the observed improvements in O2a following MCA occlusion.

Animals↗
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Modification of cerebral ischemia with Fluosol.

Fluosol-DA (Perfluorochemical Blood Substitute) was investigated in a previous study and found to provide some protection from ischemia and possible usefulness in limiting the size of infarction. In the present study, larger doses over longer periods of acute focal cerebral ischemia were used. Twenty four cats had transorbital ligation of the middle cerebral artery (MCA). The 12 experimental animals were given 20% Fluosol-DA. The control group of 12 received isotonic saline solution. Twenty-four hours after the MCA occlusion, the cats were perfused with saline and phosphate-buffered formalin. The brains were removed and immersed in 10% formalin for 2 weeks. The results of macroscopic and histological examination suggested that, although Fluosol-DA did not provide complete protection from ischemic injury to the brains of the cats treated, it may have helped to slow the development of the pathological changes.

Animals↗
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Multicenter retrospective review of results and complications of carotid endarterectomy in 1981.

A multicenter retrospective audit of carotid endarterectomies performed during 1981 was completed with 46 institutions contributing 3,328 cases. Overall, there was a 2.5% risk of transient neurological dysfunction following surgery and a 6% risk of stroke or death. The intra-institutional combined major morbidity and mortality varied from 21% to 0. Those institutions with greater than 700 beds had a statistically lower incidence of stroke or death than did other institutions. The incidence of stroke or death postoperatively was significantly lower for patients who were operated on for amaurosis fugax or for unspecified reasons. Those patients who were operated on for a progressing stroke had a higher incidence of stroke but this group was at greatest risk for stroke without surgery. The incidence of postoperative stroke or death was related to the type of arterial repair; vein patch grafting was statistically better than both fabric patch grafting and primary closure. When all patients who were not monitored during surgery were compared to all patients who had electroencephalographic (EEG) monitoring, there was found to be a significant statistical difference in favor of the EEG group. Endarterectomy combined with coronary artery bypass or simultaneous bilateral endarterectomies had a statistically significant higher incidence of stroke or death than did unilateral carotid endarterectomy.

Canada↗
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An evaluation of the effect of lidocaine in experimental focal cerebral ischemia.

In order to determine the effect of lidocaine in focal cerebral ischemia, the left middle cerebral artery was transorbitally occluded in twenty cats. Eleven received lidocaine hydrochloride intravenously. The infusion was begun half an hour prior to clip occlusion and the rate was adjusted to maintain an isoelectric EEG. Nine cats served as controls, receiving an equivalent volume of 5% dextrose 0.2% saline. Thirteen animals (7 lidocaine-treated and 6 control) were sacrificed after six hours of left middle cerebral artery occlusion without reperfusion. In the remaining seven cats, the vessel was occluded for four hours prior to sacrifice. Ischemic neuronal alteration was assessed by both histochemical (2'3'5' triphenyl-2H-tetrazolium hydrochloride reaction) and histological examination. With both durations of ischemia, there was no significant difference in the extent and severity of neuronal alterations between the lidocaine-treated and control groups of animals.

Animals↗
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Correlation between somatosensory evoked potentials and neuronal ischemic changes following middle cerebral artery occlusion.

In an attempt to determine the usefulness of evoked potentials as a measure of focal cerebral ischemia, we examined somatosensory evoked potentials (SEP's) and morphological neuronal changes in cats following unilateral middle cerebral artery (MCA) occlusion. Fifteen adult cats underwent transorbital occlusion of the MCA under halothane anesthesia. In seven cats the ipsilateral SEP's were abolished after middle cerebral artery occlusion, and did not show any recovery after 6 hours. The same seven cats showed the greatest area of moderate and severe ischemic neuronal changes, ranging from 21 to 64% (mean 39 +/- 14%) of the total ipsilateral cortical area. The remaining eight cats showed a complete flattening or decreased amplitude of the SEP after occlusion, but demonstrated a considerable recovery in the amplitude of the primary cortical potential during the six hours of the study. All these cats had ischemic areas of less than 15% (mean 9 +/- 3%) of the total ipsilateral cortex. These results demonstrate that the disappearance of the SEP and their failure to recover correlate with the extent and degree of histological cerebral ischemia.

Animals↗
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"Stump" on internal carotid artery--a source for further cerebral embolic ischemia.

A series of 9 patients have experienced hemisphere and retinal ischemia at an interval after occlusion of appropriate internal carotid arteries. All had radiological evidence of a persisting proximal stump to the occluded artery and, in most, pathological evidence of thrombotic material attached to atheromatous lesions within the stump. Thromboembolism from the stump via the anastomotic supply through ipsilateral common and external carotid arteries is thought to be responsible for the ischemic events to the brain or retina despite absence of flow through the internal carotid artery. Seven of the 9 were treated by surgical excision or obliteration of the stump and, when indicated, common and external carotid endarterectomy. Turbulence in the stump contributed to progressive atherosclerotic changes and probably aggravated thrombogenesis in this location with subsequent embolization into the anastomotic arteries.

Aged↗
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[Current management of carotid artery stenosis. What does the evidence show us?].

OBJECTIVE: Surgery of carotid artery stenosis as treatment for acute cerebral vascular accident was most used in the 1980s. This surgical procedure is one of the few to have been 'examined' to demonstrate its usefulness by means of a series of prospective multicentric trials, carried out between 1980 and 1990. This paper aims to show the results of these trials and give useful advice for current management of these patients. DEVELOPMENT: We describe the most important studies carried out to date, both in the group of patients with symptomatic and those with asymptomatic carotid artery stenosis. We emphasize the importance of achieving low morbi-mortality, both in the surgical procedure and in diagnosis. We describe the advantages and disadvantages of non-invasive methods of diagnosis, alternatives to cerebral angiography, and discuss current indications for carotid artery surgery in symptomatic and asymptomatic groups. CONCLUSIONS: The most important cooperative studies (ECST and NASCET) have shown the validity of surgical in combination with medical treatment, as opposed to medical treatment alone, in order to avoid further neurological incidents in patients with symptomatic carotid stenosis. The only cooperative study which has shown the superiority of surgical treatment, as compared with medical treatment, in a group of asymptomatic patients was ACAS (particularly in male patients).

Aged↗
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Saccular aneurysms in basilar artery fenestration.

Of 59 cases of vertebrobasilar junction aneurysms diagnosed and treated from January 1977 to April 1986, 21 (35.5%) saccular aneurysms arose in a fenestration of the proximal basilar artery. Defects of the media at the junctures of the fenestrated segments, as well as the possible presence of turbulent flow at the vertebrobasilar junction, may explain the high incidence of vertebrobasilar aneurysms associated with proximal basilar artery fenestration.

Adult↗
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Delayed CT metrizamide enhancement of syringomyelia secondary to tumor.

Six cases of syringomyelia associated with intramedullary tumor were examined by metrizamide myelography and delayed computed tomography. All cases showed opacification of syringomyelic cavities 7-24 hr after myelography. This finding suggests that metrizamide can pass through the cord substance from the subarachnoid space into a syrinx cavity in noncommunicating types of syringomyelia. It supports the theory of transneural passage of fluid as part of the origin of such cavities. These cases also support the thesis that, in patients with cord cavities, tumor can be excluded only if the cavity is demonstrated within all areas of cord enlargement.

Adult↗
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Dominant-hemisphere arteriovenous malformations: therapeutic embolization with isobutyl-2-cyanoacrylate.

Embolization treatment of 16 patients with dominant-hemisphere arteriovenous malformations (AVMs) is described. This group was selected from 50 patients with brain AVMs embolized with isobutyl 2-cyanoacrylate (IBC-2) over a period of 3 years. All 16 AVMs were cortical in location; six involved the rolandic and speech areas, and four had a deep component. Ten AVMs were embolized through a transfemoral approach, an intraoperative approach was used for four cases, and a combined transfemoral/intraoperative approach was used in two cases. Complete obliteration of the AVM was obtained in one case. Partial obliteration and complete surgical resection was obtained in three cases. Obliteration of 70%-95% of the AVM was obtained in six cases and 45%-70% of the AVM was obliterated in six cases. IBC-2 embolization of the venous drainage was observed in three cases. After embolization, eight patients remained neurologically unchanged. Three patients had mild neurologic deficits that resolved completely within 48 hr; one had a deficit that cleared up 1 week later; and one had a deficit that disappeared within 6 months. In three patients a mild permanent neurologic deficit was evident 6 months after embolization.

Adult↗
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Progressive thrombosis of brain arteriovenous malformations after embolization with isobutyl 2-cyanoacrylate.

Embolization of brain arteriovenous malformations (AVMs) with isobutyl 2-cyanoacrylate (IBCA) is an alternative to surgical treatment when dealing with large AVMs with multiple arterial feeders. The deposition of IBCA in the nidus of the AVM may produce an active and progressive thrombosis that may lead to complete occlusion of the nidus and/or to progressive thrombosis of the draining veins. Four clinical examples of progressive thrombosis after IBCA embolization are demonstrated, including two cases in which late follow-up angiography showed complete obliteration of a partly embolized AVM.

Adult↗