Using a reflectance spectrophotometer, changes in tissue hemoglobin (tHb) and oxygen saturation (tSO_2) have been measured in adult patients with moyamoya disease following STA-MCA anastomosis. It thus was found that the cortical arterial pressure in patients with moyamoya disease was significantly lower than in patients with other occlusive cerebral vascular disease (OCVD). Further, changes in the tHb in those with moyamoya disease were significantly greater than in other OCVD patients. However, no difference was seen in the tSO_2 Values between moyamoya disease and OCVD. Based on these results, it thus appears that in patients with moyamoya disease, a reduction in the blood flow due to high vascular resistance may be compensated by the enlargement of the cerebral vascular bed, such as by the development of basal moyamoya vessels and leptomeningeal collaterals. Thus, STA-MCA anastomosis may be expected to decrease the size of the moyamoya vessels and leptomeningeal collaterals and prevent bleeding from these dilated, fragile vessels.

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Patients and Methods. The authors have investigated 18 patients with a giant aneurysm and/or skull base tumor either directly or indirectly involving the internal carotid artery. Further, all patients were subjected to 4-vessel cerebral angiography with or without d carotid occlusion on the side of the lesion. The measurement of rCBF by Xenon computed tomography and recording of MSTP were performed before, during, and after a balloon occlusion test of the internal carotid artery for 15 min. In order to evaluate the vasoreactivity of the cerebral vessels, an acetazolamide-activated rCBF also was measured in each case. In 2 of the 18 patients, in whom neither a reduction nor the development of cerebral ischemic symptoms and sign were observed during test, trapping of the internal carotid artery on the lesion side was performed. The postoperative changes in rCBF at rest and the acetazolamide vasoreactivity of the cerebral vessels were also investigated in these 2 cases. Results (1) A significant reduction in the rCBF during the occlusion test was noted in the respective territories fed by the middle (MCA), anterior (ACA), and posterior (PCA) cerebral arteries, but not in the basal ganglia or the thalamus. (2) The average mSTP was 43.6±15.2 mmHg (10-100 mmHg). In cases wherein the mSTP was below 45 mmHg, the rCBF in the MCA territory, the whole hemisphere, and the basal ganglia were showed a statistically significant linear correlation with the MSTP. (3) In two cases wherein clinical manifestations of a mild cerebral ischemia took place within a few minutes after the start of the test occlusion, the rCBF and MSTP values were found to be 15-18 ml/100g/min and 30 mmHg respectively. (4) The collateral circulation through AComA or PcomA, revealed by cerebral angiography, was found to have no correlation with rCBF and MSTP during the occlusion test. (5) In cases where trapping of the internal carotid artery was performed, the cerebral vessels on the occluded side were found to manifest poor vasoreactivity in response to the intravenous administration of acetazolamide. Conclusion (1) When the MSTP fell below 45 mmHg during the occlusion test, the rCBF in the area fed by MCA became dependent on the MSTP. According1y, an MSTP of 40 mmHg appeared to be the lower limit of the CBF autoregulation. (2) The MSTP value appeared to indirectly reflect the MCA perfusion pressure. (3) The rCBF and MSTP thresholds of the ischemic symptoms and signs were found to be 15-18 ml/100 g/min and approximately 30 mmHg respectively. (4) During the internal carotid occlusion, the intracranial collateral circulation, as seen under angiography, could not help to clarify whether the cerebral ischemia due to a reduction in rCBF and the MSTP value developed. (5) It is our Impression that the degree of vasoreactivity to an acetazolamide administration, as assessed prior to the occlusion test, is important in whether a reduction in the rCBF would occur when the internal carotid artery was occluded.

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The authors report four cases of a parasplenial arteriovenous malformation (AVM), managed over the past seven years after a total removal. A11 patients were male, ranging in age from 21 to 53 years (mean age : 30 years). The AVMs were situated at the confluence of the hippocampus and the isthmus of the cingulate gyrus and the gyrus occipitotemporalis medialis. All were fed by the posterior cerebral artery and drained by the basal vein of Rosenthal, with two of these AVMs also fed by the anterior cerebral artery and drained by the medial atrial vein. A headache was the main symptom, with other symptoms, such as consciousness disturbance and a visual field defect, also being noted. In all cases, CT disclosed a parasplenial intracerebral hemorrhage with intraventricular clots. In approaching parasplenial lesions, the occipital interhemispheric, subtemporal, and transventricular routes have been employed. The use of the subtemporal approach often requires a drastic temporal lobe retraction, due to the upward slope of the tentorium. However, through this approach, the arterial side of the AVM can be attacked first. In contrast, the transventricular approach has the disadvantage of encountering the AVM at its nidus rather than at its margins, where the arterial supply enters the AVM, so that the use of this approach may result in the patient incurring a visual field defect. Therefore, all patients underwent a total AVM removal by using the occipital interhemispheric approach, With a lateral semi-prone position ipsilateral to the lesion employed to allow the brain to fall away from the falx by gravity, thereby minimizing the need for retraction. No operative mortality occurred and no neurological deficits that were not present before the surgery resulted. In conclusion, the occipital interhemispheric approach was found to be most suitable for the total removal of a parasplenial AVM because of the following advantages : 1) wide space is provided in which to work with minimal retraction ; 2) good orientation ; 3) no postoperative visual field defect ; and 4) a low risk of an air embolism.

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To clarify the mechanisms that lead to visual field defects in obstructive hydrocephalus, 28 cases of obstructive hydrocephalus (Evans' index > 0.3), caused by posterior fossa tumors, have been reviewed, and the visual fields and findings of computerized tomography (CT) and magnetic resonance (MR) imagings of each case have been examined and analyzed. Out of the 28 cases. 6 cases manifesting different visual field defects were recognized : four nasal field defects that included two bilateral nasal field defects, and two temporal field defects that included one bilateral temporal field defect. The most significant difference between patients with these defects and those without (22/28) was the width of the third ventricle (13.2±2.8 vs. 8.8±2.7) . In 4 of the 6 patients with visual field defects, the protrusion of the dilated third ventricle into the sella turcica was seen. MR imaging was found very useful for clearly revealing the stretching of the optic chiasm caused by the dilated third ventricle. It thus was concluded that the main cause of visual field defects in cases of obstructive hydrocephalus is the compression and stretching of the optic chiasm and optic tract by the protruding portion of an extremely dilated third ventricle. It also was felt that the bilateral relationship of these structures to the carotid arteries play a secondary role in the development of the type of visual field defect that each case manifested.

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The authors report the case of a subarachnoid hemonrrhage that occurred because of an aneurysmal rupture and was associated with neurogenic pulmonary edema and ventricular fibrillation in a female patient with a history of hypertension due to polycystic disease. Angiography revealed that the aneurysm had been sited at the peripheral end of the azygos anterior cerebral artery. After resuscitation, obliteration of the aneurysm and evacuation of the intracerebral hematoma were successfully performed 12 hours after onset of the rupture. The patient's subsequent clinical course was uneventful and she fully recovered without residual symptoms. The main factors that caused a deterioration of the patient's neurological condition are thought to have been pulmonary and cardiac problems. In such cases, immediate and aggressive treatment and follow-up general care enables further treatment to be performed, resulting in a favorable outcome.

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The authors report the case of giant cranial metastasis from an esophageal carcinoma that appeared three months after an esophagectomy. Within a month this metastatic tumor grew to the size of a fist. However, a successful resection was accomplished and the patient survived for over seven months. This case history thus suggests that esophageal carcinomas may metastasize and grow more rapidly than other types of carcinomas. In this report the authors also discuss the role of surgery and radiotherapy in patients with a cranial metastasis.

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The authors describe the case of a 55-year-old, male patient who was found have an angiographically occult arteriovenous malformation that had calcified, based on its appearance in skull X-rays and CT scans. The patient had been admitted to hospital due to an epileptic attack. At the time of his admission, the neurological findings were normal and his general condition was good. However, skull X-rays and CT scans showed an intracranial calcified tumor that was sited in the right temporoparietal region. Right common carotid angiography also showed an avascular mass lesion. Histopathologically, the resected specimen revealed marked hyalinazation, calcification, and a bony change on the arterial wall, as well as an organized thrombus that had filled some of the vessels. In the literature, only 8 other cases of a totally calcifled occult arteriovenous malformation have been reported. In addition to reporting the details of this case, the authors also discuss Clinical and neuroradiological characteristics of calcified occult arteriovenous malformations.

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A rare case of oculomotor neurinoma that caused intratumoral hemorrhage is described. Initial CT inspection showed a homogenous, hypodense cyst in the left parasellar region. Following a severe headache, a CT scan demonstrated intratumoral hemorrhage and a niveau formation. The subtotal removal of this neurinoma was carried out and the oculomotor nerve function improved. In the literature, 28 cases of an oculomotor neurinoma have been reported, with only two that also presented intratumoral hemorrhage.

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The authors report the case of a dissecting aneurysm of the anterior cerebral artery in a 37-year-old man, who was admitted to hospital because of left hemiparesis following a minor head injury. While undergoing clinical examinations, a CT scan revealed an area of low density corresponding to the territory of the right anterior cerebral artery. Further, a right carotid angiogram showed the dilatation of the A2 segment with a double lumen and a narrowing proximal to and distal to this dilatation. This patient was treated conservatively, and was discharged without any neurological deficits two months later. A dissecting aneurysm of the anterior cerebral artery is rare with only 10 previously cases having been reported in the literature. The clinical features, angiographic findings, and etiology of these cases are reviewed.

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Although rarely reported, lesions in the corpus callosum can cause hallucinations, and the authors present the case a patient with a falx meningioma that had compressed the body of the corpus callosum and had caused both visual and auditory hallucinations. After the complete removal of this tumor, the body of the corpus callosum recovered its normal appearance and the hallucinations disappeared. This thus suggests that compression of the interhemispheric fibers in the corpus callosum had caused these hallucinations.

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In most cases involving intraoperative angiography for the resection of arteriovenous malformations of the head, the lateral view is favored because of less overlapping of the arteries, with the patient's head fixed at a right angle to the floor, so that the central ray is perpendicular to the median sagittal plane and parallel to the floor. In this paper, the authors describe a new device that is fixed to Sugita's head frame for a lateral projection of the head and provide details of their technique for performing intraoperative angiography.

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In an effort to respond to the advancement of sophisticated operating microscopes in the aspect of magnification and brightness, ultrafine microsurgical instruments are devised. Microscissors, dissecting microprobes, and tapered retractors presented here are probably finest among those being available at present. These instruments have proved useful, particularly at the critical scenes requiring maximal magnification of the operating microscope during surgery for intracranial aneurysms, arteriovenous malformations, and deep-seated brain tumors.

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