Long-term follow-up study (more than 5 years) after posterior fossa revascularization was performed. Among 8 patients operated with superficial temporal artery to superior cerebellar artery anastomosis, 6 survived. Clinical improvement during follow-up period was obtained in 4. No recurrent ischemic attack was noted. Among 8 patients treated with extracranial vertebral artery reconstruction, 5 survived. No recurrent attacks of the posterior fossa ischemia was demonstrated. The causes of death were diabetes-associated supratentorial stroke, cardiac failure, pneumonia etc.

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Twenty-five lesions of 21 patients with atherosclerotic vertebrobasilar artery stenosis were treated with percutaneous transluminal angioplasty (PTA). These lesions included the vertebral artery ostium (VAO) in 13 lesions, the first portion of vertebral artery (V₁) in 1, second portion (V₂) in 1, forth portion (V₄) in 8, and basilar artery in 2. Patients were followed angiographically at 3-6 and 12 months after PTA. The initial success rate was 92%, but restenosis occurred in 38% (8/21) of lesions successfully treated with first PTA. Six lesions with restenosis (2 VAO and 4 V₄ lesions) were treated with second PTA, and the restenosis was recognized in 1. In total, 86% (18/21) of lesions were free of restenosis after the first or second PTA. Wall dissections were observed in 5 lesions (3 small intimal flaps and 2 pseudolumens). Based on our results, indications of PTA for vertebrobasilar artery stenosis are discussed.

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The authors report 4 operative cases of giant or large thrombosed aneurysms in the vertebrobasilar system (VB). The mean age was 53 years, with a range of 31-68 years.
Only 1 giant aneurysm on basilar artery-superior cerebellar artery junction (BA-SCA) was dead 5 months after trapping of BA. Although thrombectomy and neck clipping (NC) was performed successfully in another large aneurysm on BA-SCA, preoperative tetraparesis with cranial nerve palsy remained unchanged.
One case of giant aneurysm on the vertebral artery (VA) PICA junction who underwent NC after incomplete thrombectomy showed transient postoperative deterioration because of PICA occlusion.
One giant aneurysm on distal PICA was excised and showed remarkable improvement.
NC after adequate thrombectomy is thought to be the treatment of choice for thrombosed aneurysm in VB. But it is more difficult than the aneurysm in the carotid system because of the need to prevent injury of neighboring perforators, brainstem and cranial nerves.

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Aneurysms of the distal posterior inferior cerebellar artery (PICA) are relatively rare. The authors have encountered 14 aneurysms in 7 cases of distal PICA aneurysms. We discuss the clinical and radiological features, the problems in surgical and other treatment of this aneurysm, with reference to previous literature. In our 7 cases, 5 were discovered from subarachnoid hemorrhage due to rupture of these aneurysms. Two were nonruptured.
The angiographic appearance of 7 cases were identified; 1 congenital saccular, 2 fusiform, 1 giant thrombosed, 1 is assosiated with persistent primitive hypoglossal artery and in other 2 cases aneurysms located on the feeding artery of arteriovenous malformation (both cases had 4 or more aneurysms)
The locations of 14 distal PICA aneurysms were as follows: 2 on the anterior medullary segment, 1 on the lateral medullary segment, 1 on the tonsilomedullary segment, 5 on the telovelotonsillar segment, and 5 on the cortical segment.
Six cases of 7 were treated surgically, another 1 was a nonsurgical case because of the poor risk on admission. One of the surgical cases on the anterior medullary segment aneurysm was extirpated after OA-PICA anastomosis, which was histologically confirmed as a dissecting aneurysm.
Outcome of our cases, 3 died and the remaining 4 cases have followed excellent postoperative courses.

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We report the natural history and surgical results of unruptured cerebral aneurysms (UCAs) of the posterior circulation. This study consists of 27 patients with 28 UCAs of the posterior circulation, 17 (18 UCAs) who did not undergo surgery and 10 (10 UCAs) who did. The data obtained were compared with that from 108 patients having 138 UCAs of the anterior circulation, including 39 patients (56 UCAs) who did not undergo surgery and 69 (82 UCAs) who did. In five of the 17 patients not undergoing surgery (29.4%), the aneurysms ruptured and the patients died. Patients with UCAs that showed mass signs or ischemic symptoms (Group 3) had a high probability of aneurysm rupture. The age distribution of patients having a rupture was 3 under 59 years, 2 between 60 and 69 years, and none over 70 years. The mean size of ruptured UCAs was 14.2mm in diameter (range: 5-30mm). UCAs of the posterior circulation had a higher risk of subsequent rupture than those of the anterior circulation: 29.4%vs. 15.4%. Although no operative mortality occurred, morbidity appeared in 4 patients (40%) including 2 transient (20%) and 2 permanent (20%) neurologic deficits. The two permanent deficits occurred in patients with giant aneurysms, one of whom was elderly. The morbidity rate was higher in patients undergoing surgical treatment of UCAs of the posterior circulation than those having surgery for aneurysms of the anterior circulation: 40%vs. 8.7%. If possible, UCAs of the posterior circulation should be treated surgically; however, the procedures should be chosen carefully, especially for elderly patients and those with large or giant aneurysms.

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The authors present 33 patients with dissecting aneurysm of the intracranial vertebral artery, of whom subarachnoid hemorrhage developed in 26 patients and cerebral ischemia in 7 patients. Sixteen patients were surgically treated and 17 were conservatively treated. In this series, recurrent hemorrhage occured in 9 (35%) of 26 patients who presented with subarachnoid hemorrhage within 2 weeks after the initial ictus. The outcome of the cases with recurrent hemorrhage was very poor-7 of these 9 patients died. Therefore, surgical intervention during the acute stage is required to avoid the early rerupture. Comparative study with surgical and conservative treatment for dissecting aneurysms of the vertebral artery indicated that the outcome of patients with surgical treatment was much better than with conservative treatment. In surgical procedures, proximal clip-occlusion of the vertebral artery at the site distal to the PICA (DTP) was performed in 5 cases, at proximal to the PICA (PTP) in 4, trapping of the vertebral artery with dissecting aneurysm in 2, coating in 3, and proximal occlusion of the vertebral artery with detachable balloon in 2 patients. Postoperatively, transient lower cranial nerve palsy or cerebellar signs developed in 2 cases with trapping, in 1 with PTP and permanent hemiparesis due to thromboembolism at the top of the basilar artery in 1 with balloon-occlusion of the vertebral artery. In spite of surgical intervention, rerupture occured postoperatively in 1 case with coating and in 1 with DTP. Trapping procedure is most reliable to prevent rerupture of dissecting aneurysm, but it is difficult to expose the distal part of the vertebral artery beyond the aneurysm for trapping. Although proximal clip-occlusion is not completely satisfactory for prevention of rebleeding, it is simple as a method and useful for dissecting aneurysm of the vertebral artery.

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Clinical characteristics of 20 patients with arteriovenous malformations of the posterior fossa were investigated. Nineteen of 20 patients presented with intracranial hemorrhage (intra-cerebellar and/or subarachnoid hemorrhage), which was recurrent in 5 cases (26%). One patient demonstrated progressive neurological deficits. AVM located in the cerebellar hemisphere in 10 patients, vermis in 7, tonsil in 1, and brain stem in 2. Four of 20 patients (20%) had concomitant aneurysms relating to the feeding arteries of AVM.
Operative intervention was directed at primary excision in 16 patients, total excision in 14, subtotal excision in 1, and partial excision and feeder clipping in 1. One patient underwent ventricular drainage only. This patient died of recurrent hemorrhage 11 days after the drainage. Three patients did not receive any treatment, and 1 of 3 patients died of pneumonia. Seventeen of 20 patients (85%) had a good result, 1 patient (5%) a poor result, and 2 patients (10%) died. Good results could be expected of surgery in the treatment of AVM localized in the cerebellar hemisphere.

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The arachnoidea between the superficial sylvian vein and the temporal lobe is incised, and the bridging veins flowing from the temporal lobe to the superficial sylvian vein and those at the temporal tip are cut. Thus, the temporal lobe is separated from the superficial sylvian vein. The anterior temporal artery is separated from the temporal lobe. These treatments increase the mobility of the temporal lobe. The sylvian fissure is widely opened by compression of the temporal lobe with a spatula placed under the anterior temporal artery. This approach provides good access to the lesions in the interpeduncular cistern.

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During 2.5 years after introduction of MRI, we have experienced 9 cases of vertebral dissecting aneurysm (VDA) that initially appeared with the signs and symptoms of subarachnoid hemorrhage. The patients' age ranged from 40 to 70 years (average: 51.8 years), and 6 male and 3 female patients were included in this series. Five of the 9 patients were hypertensive and 1 had an episode of CVA (internal carotid occlusive disease). It was particularly noteworthy that abducens palsy was observed in varying degrees in 8 cases immediately after the SAH symptoms.
Lower cranial nerve palsy was also observed in 2 elderly cases. On MRI, VDA consistently showed high signal intensity around eccentric signal void. However, the intimal flap and double lumen could not be confirmed. Angiography demonstrated a fusiform dilatation of the vertebral artery with irregular surface on it and either narrowing or tapering in vascular diameter was found adjacent to the dilated portion.
VDA with the onset of SAH was characterized by these MRI and angiographic findings.
In 4 cases, VA was surgically ligated following balloon occlusion test. Coating of VDA was performed in 2 cases while conservative treatment was chosen for 2 cases. The outcome in the 9 month to 2 year follow-up study was good or excellent except for 1 case that resulted in death with a complication of early recurrent hemorrhage within 5 days after its onset. Based on our results in this series, it was considered that vertebral dissection tends to extend to the basilar artery particularly in aged patients with atherosclerosis, and so conservative treatment seems to be preferred for these elderly cases. For relatively younger cases, proximal ligation should be chosen in stable chronic stage, for spontaneous occlusion is not rare in these cases.

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