We discribe the occipital interhemispheric approach for an aneurysm on the distal posterior cerebral artery (PCA). The absence of adhesion of the occipital lobe to the falx and few bridging veins allow easy dissection between the bilateral occipital lobes. Utilization of gravity, osmotic agents, and removal of the cerebrospinal fluid provide an interhemispheric slot wide enough to observe and clip the aneurysm. Through the approach the proximal PCA, an aneurysm, and the distal PCA are located vertically as the middle cerebral artery and its aneurysm through the distal trans-Sylvian-fissure approach.

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The natural history of intracranial dissecting aneurysms is not precisely known. Therefore, it is difficult to decide how to manage this disease. This study focused on the analysis of patients with unruptured intracranial dissecting aneurysm of the vertebrobasilar (V-B) system.
The serial angiographic findings and the long-term outcome of 12 consecutive patients presenting with ischemia/infarction and/or headache were analyzed. Two patients had multiple dissecting aneurysms. Three patients were treated surgically and the other 9 were treated conservatively (rigorous control of blood pressure/no anticoagulants). The mean follow-up period was 4.2 years.
Males were predominant (10:2) and the mean age was 42.6 years in the 12 patients. Ten arterial dissections occurred in the vertebral artery (2 extended to the basilar artery), 3 in the posterior inferior cerebellar artery and 1 in the posterior cerebral artery. Pearl and string sign was the most common finding and fusiform dilatation and retention of the contrast media in the venous phase were also frequently observed on the initial angiography. On the serial angiography, improvement or normalization of the arterial configuration was observed in 4 of 6 arterial dissections (67%). In 1 patient, enlarged arterial dissection was observed on the serial angiography and was treated by intravascular surgery, using the detachable balloon. Long-term follow-up was available in 11 patients (two treated surgically and 9 conservatively). Ten of the 11 patients (91%) achieved good recovery and returned to work. One patient, who had a second attack of ischemia and was admitted in semicoma, became severely disabled ultimately on 9-years follow-up. No more recurrence of ischemia or associated subarachnoid hemorrhage occurred in any of the 11 patients.
These results suggested that unruptured intracranial dissecting aneurysms of the V-B system were mostly correlated with a benign clinical course, and could be treated conservatively. It is stressed that surgical intervention, including intravascular surgery, should be considered when enlarged dissection has been observed on the serial angiography.

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We experienced 63 cases with carotid endarterectomy (CEA). After CEA, 54 cases (86%) showed clinical improvement or no change, 6 cases (9%) showed transient complications and 3 cases (5%) suffered sutained complications. Complications consisted of 2 subcutaneous hemorrhages, 5 lower cranial nerve palsies, 2 myocardial infarctions, 2 convulsions and hemiparesis, 2 slight impairments of consciousness and one secondary glaucoma.
Among 6 patients with complications such as myocardial infarction, glaucoma, convulsion and declined consciousness except for the ones due to surgical maneuvour, we analyzed the risk factors such as age, preoperative ischemic condition, CT and MRI findings, multiple operations and the degree of stenosis of ipsilateral carotid artery on the operative side. Severe carotid stenosis over 90% was the most significant risk factor in carotid endarterectomy. It correlated with hyperperfusion syndrome, myocardial infarction and mental impairment. One patient with severe carotid stenosis presenting ischemic ocular syndrome had glaucoma in spite of improvement of ophthalmic circulation after CEA. These data suggested that in CEA for severe carotid stenosis over 90%, the patients should be more intensively cared for during the postoperative period.

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Recent technical advancements in spiral computerized tomography (CT) imaging allow exellent three-dimensional visualization of the intracranial larger vessels. In the present study, we compared three-dimensional CT angiography (3D-CTA) with digital subtraction angiography (DSA) to clarify the clinical usefulness of this new imaging technique for surgical planning in patients with unruptured cerebral aneurysms, referring to intraoperative findings. 3D-CTA was performed on 15 patients with 21 unruptured aneurysms who underwent operation for these aneurysms, using a SOMATOM PLUS-S scanner. We employed the shaded surface rendering method for three-dimensional reconstruction with the threshold of 80-150 HU and maximum intensity projection (MIP) processing. In 11 out of 21 aneurysms, images obtained from 3D-CTA were superior to those from DSA for surgical planning, while in only 3 aneurysms 3D-CTA was considered to be less useful due to overlapping with bony and vascular structures. 3D-CTA provided valuable information for surgical simulation as follows: 1) Good delineation of actual shape of the dome and the neck, 2) better understanding of the direction of the aneurysm and its anatomical relationship with surrounding major arteries and bony structures, 3) easy visualization of intramural calcification around the neck using MIP technique. In cases with cavernous sinus aneurysms, the intradural projection of the aneurysm can be made visible by elevating the threshold up to 250 HU. On the other hand, several potential limitations to the use of 3D-CTA such as poor demonstration of small branches and perforators and overlapping with venous and bony structures existed. In conclusion, although further improvement and adequate clinical experience of 3D-CTA are needed, this noninvasive method has proved to be valuable for planning in aneurysm surgery.

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[Purpose] Advances of intravascular neurosurgery and the introduction of radiosurgery have been changing the treatment strategy for arteriovenous malformation (AVM). We review our original method of embolization and evaluate the initial results.
[Methods] This study is based on 138 cases of AVM treated with embolization. Clinical presentation was hemorrhage in 87, convulsion in 36, and others in 15. Embolization using estrogen alcohol (EA) followed by polyvinyl acetate (PVac) was utilized. Fifteen patients were followed by direct surgery and 87 by gamma knife.
[Results] Complete obliteration was obtained in 12 patients (8.6%) by embolization alone. Recanalization was not observed in an embolized area at follow-up. Fifteen patients with partial embolization underwent direct surgery and 12 were completely cured. The embolized area was soft and easily resectable. The volume of AVM before and after embolization was evaluated in 87 patients treated with gamma knife. Mean volume was decreased from 11.8 ml before embolization to 5.7 ml after it. Early follow-up of cases that received gamma knife treatment suggests that embolization accelerated the latent period of cure and expanded the indication of gamma knife therapy. The mortality rate was 0.7%, and major and minor morbidity rate was 6.5% and 10.1%, respectively. Overall rebleeding rate of 138 cases was 2.8%/year.
[Conclusion] Embolization using EA and PVac cures 8.6% of cases and facilitates surgical removal and radiosurgical treatment. A treatment strategy combing these three modalities is presented.

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We report changes in cerebral blood flow of 16 patients with putaminal hemorrhage (6 operated and 10 non-operated cases), followed-up for 6 months after hemorrhage. Patients with hypertensive putaminal hemorrhage were selected for our study by the following criteria: patients without previous cerebrovascular, or cardiopulmonary disease, with neurological grades of 1-3, with hematoma volume of less than 25 ml, and younger than 70 years of age. Mean cerebral hemisphere blood flow was measured by ¹²³I-IMP SPECT with arterial blood drawing within 1 week, at 2, 4, 8 weeks and 6 months after onset. Those patients whose neurological conditions did not improve during the first week after onset were operated upon stereotaxically using Komai's stereotaxic frame. Cerebral blood flow of contralateral cerebral hemisphere of the operated group (6 cases) at 1, 2, 4, 8 weeks and 6 months after onset were 27.6, 36.1, 30.2, 35.8, 46.8ml/100g/min, respectively. Those of hemorrhaged cerebral hemisphere of the operated group were 24.6, 31.8, 26.7, 32.2, 39.9. Cerebral blood flow of contralateral cerebral hemisphere of the non-operated group (10 cases) were 42.7, 33.8, 38.8, 32.9, 29.4, and those of hemorrhaged hemisphere of non-operated group were 38.8, 30.4, 35.8, 30.2, 28.8. Compared to the non-operated patients cerebral blood flow of hemorrhaged and contralateral cerebral hemisphere of operated patients were decreased only during the first week after putaminal hemorrhage. These differences were statistically significant. At 6 months after onset, cerebral blood flow of the hemorrhaged and contralateral cerebral hemispheres of operated patients was higher than that of non-operated patients, and these differences were statistically significant. Changes in cerebellar blood flow showed the same tendency as cerebral blood flow in both the operated and non-operated group. Therefore, operation was effective to improve cerebral blood flow of hemorrhaged and contralateral cerebral hemispheres at 6 months after putaminal hemorrhage. Furthermore, cerebral blood flow of the hemorrhaged hemisphere correlated well with that of whole brain including the cerebellum. We speculated that decreased cerebral blood flow of the contralateral cerebral hemisphere and the cerebellum was due to transneural depression.

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We studied cases of 60 patients with 64 infraclinoid aneurysms surgically treated and classified these aneurysms into 3 groups based on surgical findings. Group I was infraclinoid aneurysms located distal to the dural ring and projected ventromedially. Group IA are distal to the origin of ophthalmic artery and Group IB are proximal to the artery. These Group I aneurysms originated below the level of the anterior clinoid process on the lateral view of carotid angiogram but these are truly subdural aneurysms and may cause subarachnoid hemorrhage. Group II aneurysms are located between the distal (dural) ring and the proximal ring. Group IIA are occurred at the medial surface of the internal carotid artery and Group IIB are occurred at the lateral surface. Those of Group III are central to the proximal ring and projected laterally. Group III aneurysms are genuine intracavernous aneurysms. These classifications are extremely useful for selection of operative candidates and surgical procedures.

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We report 3 cases of cavernous angioma in the brain stem that were operated on.
Case 1 was a 25-year-old female who had a history of 4 episodes of a pontine hemorrhage. MRI demonstrated a cavernous angioma in the dorsal pons. A suboccipital craniectomy was performed and a transfourth ventricular approach was used to expose the cavernous angioma. No abnormal findings, such as staining of hemosiderin, were observed at the floor of the 4th ventricle. The facial colliculus and the median sulcus of the floor were considered to be useful landmarks in approaching the cavernous angioma. But the facial colliculus could not be identified on the surface of the 4th ventricle floor. Therefore EMGs of the m. orbi. oris. were monitored to find the location of the facial colliculus by electrical stimulation of the 4th ventricular floor. After confirming the facial colliculus, the angioma was removed successfully and safely. Postoperatively, no additional neurological deficits were seen.
Case 2 was a 37-year-old male who experienced a pontine hemorrhage 2 times. MRI demonstrated a cavernous angioma in the dorsal pons. Although the cavernous angioma was totally excised, the patient exhibited facial palsy and truncal ataxia.
Case 3 was a 27-year-old male who experienced a brain stem hemorrhage. MRI demonstrated a cavernous angioma in the medulla oblongata. A suboccipital craniectomy and C1 laminectomy were performed. A small incision was made along the median sulcus at just rostral to the obex and the angioma was removed successfully. During manipulation near the obex, transient hypotension and bradycardia were observed transiently. Postoperatively, the patient was discharged without having any additional dificits and followed a satisfactory postoperative course.
Because of the risk of repeated hemorrhage, symptomatic brain stem cavernous angiomas should be removed surgically. In operations, it is important to take a safe pathway to the lesion. However, it is difficult to find landmarks to the lesion on the surface of the 4th ventricular floor. We used EMG monitoring of the m. orbi. oris. by stimulating the 4th ventricular floor to find the location of the facial colliculus. The facial colliculus was a good landmark to approach the lesion in the dorsal pons.

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We report a case of dural arteriovenous fistulae in the posterior fossa successfully treated by transvenous direct embolization. This 55-year-old male presented with repeated episodes of alexia, followed by pulsatile tinnitus and headache in December 1992. Cerebral angiography revealed a dural arteriovenous fistulae at the left sigmoid sinus fed by tiny branches of occipital artery. The fistulae drains through the vein of Labbé and internal cerebral vein, into the cavernous sinus and superior sagittal sinus. The proximal and distal part of the sigmoid sinus was occluded. First we tried to obliterate the fistulae by transarterial embolization with PVA particles, which reduced shunting flow and ameliorated the symptoms immediately. The symptoms, however, recurred one week after the treatment because of the recruitment of dural collateral vessels. Next we selected transvenous direct embolization under small retro-mastoid craniectomy. Thirteen stainless steel coils were placed in the affected sinus, and abnormal vascular network disappeared completely without occluding normal venous pathways. The patient remains symptom-free, and the repeated cerebral angiograms performed six months after the second treatment demonstrated no definitive abnormality. From our experience and review of the literature, transvenous embolization appears to be the less invasive and more curative treatment of arteriovenous fistulae in the posterior fossa.

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