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Vertebrobasilar occlusion therapy of giant aneurysms

Significance of angiographic morphology of the posterior communicating arteries

David M. Pelz, Fernando Viñuela, Allan J. Fox, and Charles G. Drake

✓ The clinical and angiographic records were reviewed for 71 patients with giant aneurysms of the posterior circulation, who underwent therapeutic occlusion of the basilar artery or both vertebral arteries. This treatment is used when the aneurysm neck cannot be surgically clipped, and occlusion of the parent artery is performed to initiate thrombosis within the lumen. In these cases, collateral blood flow to the brain stem is supplied mainly by the posterior communicating arteries. Consequently, their angiographic morphology (patency, size, and number) is demonstrated as a preoperative indicator of whether the patient will be able to tolerate vertebrobasilar occlusion. Vertebral angiograms with carotid artery compression (the Allcock test) will often be needed to provide this information.

The data relating posterior communicating artery morphology to clinical outcome in 71 cases of attempted vertebrobasilar occlusion are presented. The use and accuracy of carotid artery compression studies are also discussed. It is essential for the radiologist to supply the neurosurgeon with this valuable information in every case of giant posterior circulation aneurysm.

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Fernando Viñuela, Allan J. Fox, David M. Pelz, and Charles G. Drake

✓ Fourteen patients had classical angiographic findings of intracranial dural arteriovenous malformations (AVM's). They presented with unusual central neurological signs and symptoms, including visual disturbances, hemiparesis, speech disturbances, gait ataxia, diffuse increased intracranial pressure, and intracranial hemorrhage. In 12 of the 14 patients there was a direct correlation between the clinical presentation and the venous drainage characteristics of the AVM's. The symptoms were probably related to a regional steal phenomenon in two patients. Six patients had direct surgical excision of the dural AVM. Five patients underwent endovascular embolization of the malformation and, in one case, the AVM was removed surgically after embolization. In one patient, the external carotid artery in the neck was ligated. Ten of the 14 patients had substantial clinical improvement or cure. A complete anatomical obliteration of the malformation was obtained in seven cases. None of the patients deteriorated clinically after therapy.

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Fernando ViñUela, Charles G. Drake, Allan J. Fox, and David M. Pelz

✓ An intracranial varix is rare and has been associated mostly with vein of Galen fistulae or arteriovenous (AV) malformations. The authors present eight cases of intracranial, pial or subpial AV fistulae with concomitant giant varices. Six were supratentorial and two were infratentorial. Only one case involved the vein of Galen. In six cases successful surgical and/or endovascular occlusion of the intracranial AV fistula was obtained, and one case was treated conservatively. Staging of surgery and postoperative hypotension were considered to be important in avoiding edema and hemorrhage following obliteration of a large AV shunt. One patient died from delayed postoperative intracerebral bleeding.

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Fernando Viñuela, Luis Nombela, Margot R. Roach, Allan J. Fox, and David M. Pelz

✓ Angiograms obtained prior to treatment in 53 cases of deep-seated cerebral arteriovenous malformations (AVM's) were retrospectively analyzed with particular attention to the topography of the AVM nidus and the venous drainage. The location of the lesion was determined by a combination of angiography and computerized tomography. Twenty-seven AVM's involved the basal ganglia and thalamus, 12 were located in the corpus callosum, six were intraventricular, and eight involved the mesencephalon and brain stem. Forty-one patients (77.3%) presented with intracranial hemorrhage. Vessel wall irregularities and/or stenosis of the system of the vein of Galen were observed in 14 cases, and occlusion of the deep venous system was present in seven cases. These AVM's showed numerous collateral venous pathways through enlarged medullary and cortical regional veins. There was dominant participation of the basal vein of Rosenthal in all cases. Unique local hemodynamic factors produced by the convergence of the draining veins of the AVM's into the vein of Galen and straight sinus may lead to a higher incidence of stenosis and/or occlusion of the venous drainage. The relatively high incidence of intracranial hemorrhage in these deep-seated AVM's may suggest a relationship between an increased incidence of intracranial bleeding and impaired venous outlets.

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Allan J. Fox, Fernando Viñuela, David M. Pelz, Sydney J. Peerless, Gary G. Ferguson, Charles G. Drake, and Gerard Debrun

✓ Of 68 patients with unclippable aneurysms treated by proximal artery occlusion with detachable balloons, permanent occlusion was achieved in 65; of these patients, 37 had carotid artery aneurysms below the origin of the ophthalmic artery, 21 had aneurysms arising from the supraclinoid portion of the carotid artery, six had basilar trunk aneurysms, and one had a distal vertebral aneurysm. Examination for treatment selection included assessment of the circle of Willis by compression angiography and xenon blood flow studies, with the ultimate evaluation being test occlusion under systemic heparinization with the balloon temporarily placed in the desired position. Of 67 patients who underwent a formal occlusion test, eight with carotid artery aneurysms did not initially tolerate the occlusion test, and ischemic signs disappeared instantaneously with deflation and removal of the balloon. During test occlusion, two additional patients had ischemic events that proved to be embolic; these reversed immediately upon balloon deflation.

Of the 65 patients in whom permanent occlusion was effected by detachable balloon, there were nine instances of delayed cerebral events. One of these was a seizure leading to respiratory arrest and resuscitation 3 days following occlusion in a patient who had presented with seizures. The other eight cases were delayed ischemic events; seven were completely reversed and one patient had residual weakness in one leg (1.5% permanent morbidity). Extracranial-intracranial bypass procedures were performed in 25 of the 65 cases. All aneurysms of the carotid artery below the level of the ophthalmic artery presented angiographic proof of complete thrombosis. Ten of 21 aneurysms arising from the supraclinoid portion of the carotid artery were completely thrombosed by proximal occlusion alone, without additional trapping procedures. Similarly, in three of six basilar trunk aneurysms, proximal occlusion alone initiated complete aneurysm thrombosis without trapping. The conclusion is that proximal balloon occlusion for unclippable cerebral aneurysms is a convenient, safe, and effective way of producing arterial occlusion in these cases.