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  • Author or Editor: Garnette R. Sutherland x
  • By Author: Vezina, William C. x
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Garnette R. Sutherland, Martin E. King, Charles G. Drake, Sidney J. Peerless and William C. Vezina

✓ Turbulence within cerebral arteriovenous malformations (AVM's) may lead to endothelial disruption, platelet aggregation, and thrombus formation. This hypothesis would account for many of the pathological features in AVM's, including intimal hyperplasia and arterial thrombosis with or without organization. In this study, a dual-isotope method employing indium-111-labeled platelets and technetium-99m-labeled red blood cells was used to evaluate in vivo platelet aggregation in 20 patients with AVM's. The use of two isotopes allows subtraction of the blood-pool platelets and calculation of the ratio of the indium deposited:the indium in the blood pool (In(D)/In(BP)).

After a 24-hour incubation period, eight of the 20 patients demonstrated platelet aggregation in their AVM's with a mean In(D)/In(BP) ratio of 0.71 ± 0.36 (± standard deviation). Seven of these AVM's were available for pathological study and all of them demonstrated evidence of arterial thrombosis of variable age. In the remaining 12 patients, the In(D)/In(BP) ratio was not significantly elevated (mean 0.02 ± 0.13), indicating the absence of active platelet aggregation during this short interval of study. Five of these AVM's were pathologically examined, four of which showed evidence of arterial occlusion. It is concluded that platelet aggregation is a common occurrence in cerebral AVM's and may account for the dynamic histopathology often seen in these lesions.

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Garnette R. Sutherland, Martin E. King, S. J. Peerless, William C. Vezina, G. William Brown and Mike J. Chamberlain

✓ Turbulence within intracranial aneurysms may result in tearing of the aneurysmal wall, exposing the subendothelial matrix to circulating platelets. In this study, platelet interaction in giant intracranial aneurysms was evaluated by a dual-isotope technique employing 111In-labeled platelets and 99mTc-labeled red blood cells. The use of two isotopes allows the subtraction of the blood pool and the calculation of the ratio indium deposited:indium blood pool (In(D)/In(BP)). A ratio greater than zero indicates platelet deposition within the aneurysm.

Thirteen patients were evaluated in this way, with platelet deposition demonstrated in six. In these six patients, the ratio In(D)/In(BP) was found to be significantly elevated, with a mean value of 0.96 ± 0.65. Three of these six patients had symptoms of recurrent transient neurological deficits; one of these three suffered a complete stroke following documentation of platelet deposition. In this case, the aneurysm was obtained at surgery and was found to contain intraluminal platelet aggregation when viewed by scanning electron microscopy. In the remaining seven patients, the ratio In(D)/In(BP) was found not to be significantly elevated (mean −0.03 ± 0.06), indicating the absence of active platelet deposition. Two of these patients had prior symptoms of cerebral ischemia; one of these was found to have an ulcer in the ipsilateral internal carotid artery which was probably responsible for thromboembolic events to the hemisphere.

The authors conclude that platelet aggregation occurs more frequently than previously recognized in giant intracranial aneurysms, and their data substantiate the hypothesis that platelet metabolic products or thrombi originating from a large aneurysm may embolize to distal cerebral vessels.