Both the cortico-spinal MEP and cortico-muscular MEP, which directly reflect the pyramidal function, were recorded in 25 cases of hypertensive intracerebral (putaminal) hematoma. In all cases, over 70% of the hematoma was aspirated by a CT-guided stereotaxic operation within 72 hours of onset. The effects of hematoma aspiration on the cortico-spinal MEP and the corticomuscular MEP were also evaluated.
The D-wave of the cortico-spinal MEP was recordable in 19 cases, while the other 6 cases showed no response before aspiration of the hematoma. Among these 19 cases, 15 revealed an increased amplitude and/or shortened latency of the D-wave after aspiration of the hematoma. The long-term prognosis for motor function was good in cases that showed a D-wave of the cortico-spinal MEP; however, it was bad in the 6 cases that had no D-wave. A magnetic transcranial cortico-muscular MEP was recordable in only 8 cases, while the other 17 cases exhibited no response before aspiration of the hematoma. The D-wave of the cortico-spinal MEP was recordable in all cases of grades 1-5 and in 1 case of grade 0 by the muscle maneuver test (MMT); however, no magnetic transcranial cortico-muscular MEP was recordable in all cases of grades 0-2 and in half the cases of grade 3.
The present results suggest that hematoma aspiration effectively reduces the compression effects of a hematoma against the pyramidal tracts, and that monitoring of the cortico-spinal MEP is useful for assessing the prognosis of the motor function. Further, the cortico-spinal MEP has advantages for assessing the motor function as compared with the magnetic cortico-musular MEP.

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The authors report their surgical treatment of 14 cases of vertebrobasilar fusiform (or dissecting) aneurysm. Proximal clipping was used in 4, trapping or resection in 3, clipping in 4, and wrap-clipping in 3 cases. Morbidity and mortality were experienced only in trapping or resection cases. These complications were analyzed and the authors concluded that obliteration of perforators to the brain stem was the cause. A multidirectional approach to the lesion and intraoperative determination as to the presence or absence of perforators coming off from the aneurysm are important to avoid these complications. If perforators are not found to come off from the aneurysm, the wrapclipping method is the treatment of choice for these aneurysms. Among the several materials (i.e. muscle fascia, dura, dacron-meshed silastic sheet) used for wrapclipping, the dacron-meshed silastic sheet was most useful. The dacron mesh covering the surface of the sheet is helpful to avoid slipping out of the clip that is pinching a part of the dome of the fusiform aneurysm. The silastic sheet is transparent enough to adjust the caliber of the parent artery and easily tailored to spare the branching vessels. The surgical techniques are described together with a literature review as to the pathological relationship between the fusiform and the dissecting aneurysms.

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Forty-five non-surgically managed patients with vertebrobasilar (V-B) aneurysm were studied to elucidate the clinical features and long-term outcome. The patients were classified into the following 3 groups. Group S had 23 patients with saccular aneurysm, group F, 10 with atherosclerotic fusiform aneurysm, and group D, 12 with dissecting aneurysm. The patients in group D were significantly younger than the others (p<0.05). The majority of the patients were male in both group F and group D. Basilar bifurcation aneurysms were most commonly observed in group S (43%), while the vertebral artery was frequently affected in both group F and group D. On the long-term follow-up, only 1 patient died of subsequent aneurysmal rupture (6%) and 5 died of other medical problems in group S. The annual risk of bleeding was 0.7%. Deterioration of symptoms was found in 5 of 6 patients (83%) in group F. Three died from pulmonary or cardiac complications, but none died of aneurysmal rupture. On the contrary, good outcome and no deterioration of symptoms were obtained in group D. These results indicate that the clinical features considerably differ in the 3 groups. We emphasize that the medical management and advanced surgery, including intravascular intervention, are essential to achieve better outcome in patients with V-B saccular aneurysm. Based on our findings, V-B dissecting aneurysms should be managed conservatively, unless they continue to grow on follow-up angiograms.

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Four cases with dural arteriovenous fistulas (AVFs) of the posterior fossa were treated by endovascular surgery. The dural AVF of case 1 (type-II in Piton's classification) recanalized soon after the transarterial embolization and the affected sinus was finally resected surgically. Case 2, with a multicomponent dural AVF (type-III) in the transverse-sigmoid sinus and foramen magnum, was treated by 3-staged endovascular surgeries. The first transarterial embolization markedly reduced the blood flow of the transverse-sigmoid sinus. Since the sinus was occluded by each side, it was packed with coils by craniotomy. The dural AVF involving the foramen magnum was obliterated by transvenous embolization through a femoral route. The transverse-sigmoid sinus of case 3 (type-III) was also occluded by each side, and embolized by craniotomy under the local anesthesia. The sigmoid sinus of case 4 (type-I) was obliterated by transvenous embolization under the flow restriction by temporary balloon occlusion of the main feeding artery. It is obvious from our result that the transvenous embolization is a more radical endovascular treatment for the dual AVF of the posterior fossa. The transarterial embolization is considered a potent procedure as a supplementary method of the transvenous embolization.

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The authors evaluated surgical outcome and natural history of the arteriovenous malformation (AVM) in the posterior fossa according to anatomical location of the AVM. Seventeen patients with AVM in the posterior fossa have been managed at our department since 1970, 14 of whom presented with intracranial hemorrhage, and 3 presented progressive focal symptoms. Out of 17 patients, 10 of the AVM were located in the cerebellum, 4 in the cerebellopontine angle (CP-angle), and 3 within the brainstem. In the 10 cerebellar AVM, operations were directed at primary resection in 9 cases, and 1 patient refused operation. Six out of 9 cases had good results and 3 had significant morbidity. In the 4 CP-angle AVM, 2 patients underwent direct operations with good results. In the 3 brainstem AVM, 1 patient with epipial AVM underwent an operation with good result. In the non-surgical group, 3 out of 5 patients died.
The AVM located in the cerebellum are resected safely, and epipial or subpial AVM in the CP-angle or brainstem are resectable with acceptable morbidity. The deep-seated brainstem AVM would have a poor natural history.

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The authors report their operative results of 6 arteriovenous malformations (AVM) in the cerebellopontine angle (CPA) in patients aged 11 to 34 years. Five of them presented with hemorrhage and 1 with dizziness.
Operative results are most influenced by the preoperative neurological state. Two patients have no permanent postoperative deficits, 3 have moderate or mild deficits and 1 died. The single death resulted from preoperative severe damage of the brainstem. The operative approach depends on the main feeder of AVM. When the main feeder is the anterior inferior cerebellar artery (AICA) and/or posterior inferior cerebellar artery (PICA), the lateral cerebellar approach is selected. In the case of the superior cerebellar artery (SCA), the subtemporal transtentorial approach is selected. The combined approach is employed for the large AVM fed by AICA, PICA and SCA. Direct surgery is the treatment of choice for CPA-AVM presented with hemorrhage.

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Neck clipping of the basilar bifurcation aneurysm was performed in 32 cases during a 5-year period (1988-1992). The size of the aneurysms varied from 3 to 16mm in diameter and the height of the aneurysm neck ranged from 5mm below to 15mm above the posterior clinoid process. Surgical outcome was excellent in 17 cases, good in 13, fair in 1, poor in 1. These cases were analyzed based on the following aspects: I. approach route, II. extradural procedures, III. intradural procedures, IV. selection of clips.
I. The aneurysms were approached through the opticocarotid route in 6 cases, the retrocarotid route in 21 and the subtemporal route in 5. II. As the extradural procedures, the following were effective to provide wider surgical field: 1. zygomatic osteotomy (n=4), 2. optic unroofing (n=3), 3. drilling of the posterior clinoid process (n=3), 4. section of tentorium (n=5). III. As the intradural procedures, the following had the advantage for better visualization of the aneurysm neck: 1. section of the bridging vein from the temporal pole (n=5), 2. separation of the anterior temporal artery (n=2), 3. direct retraction of the posterior cerebral artery (n=7), basilar artery (n=2) and aneurysm (n=3), 4. preservation of perforating arteries with silicone sheet (n=2). 5. temporary clipping of the basilar artery (n=17), 6. section of the posterior communicating artery (n=3), 7. tentative clipping (n=2). IV. Multiple clipping was performed in 2 cases. The following clips were often used: a mini-clip (n=4), a clip with long blades whose length were more than 15mm (n=13), a straight fenestrated clip (n=3).
The above-mentioned techniques are recommended as surgical options to preserve perforators, which is important to obtain for basilar bifurcation aneurysm.

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Edematous swelling due to occlusion of the vertebrobasilar artery and its branches can produce a large cerebellar lesion that compresses the brain stem and rapidly lead to coma and death. To investigate the optimum therapy of cerebellar infarction, 139 patients with acute ischemic symptoms of the vertebrobasilar territory were studied. Computerized tomography was helpful in diagnosis and treatment of the patients. In 25 patients, cerebellar infarction was accompanied by obstructive hydrocephalus resulting from acute compression of the pathway of the cerebrospinal fluid. Although ventricular drainage was effective in some of them, immediate surgical decompression of the posterior fossa was needed to ensure not only life saving but also useful social activity, if the brain stem was not extensively involved. In the other patients without obstructive hydrocephalus, symptoms due to brain stem compression never developed even if the size of the infarction was large. It is concluded that development of obstructive hydrocephalus is a good indicator in selecting surgical treatment for patients with cerebellar infarction.

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A series of 70 patients with idiopathic cerebellar hemorrhage diagnosed by computerized tomography (CT) is described. The authors studied the factors influencing the outcome of cerebellar hemorrhage. The patients were followed up 3 months after discharge, and the outcomes at discharge and 3 months after discharge were studied. The relationships of outcome with the level of consciousness on admission, with the hydrocephalus, with the volume of hematoma and with the age of patients were analyzed individually. The prognosis of surgical treatment was compared with that of conservative treatment.
Many of the patients with a Japan Coma Scale (JCS) score of 10 or less tended to achieve good recovery and the patients with a JCS score of 30 or more tended to have a poor prognosis. The outcome of patients with large hematoma (31ml or more) were worse, especially in the group of conservative treatment. The level of consciousness on admission and the volume of hematoma were good guides in predicting outcome. The hydrocephalus was affected by the volume of hematoma and affected the level of consciousness. The prognoses of aged patients older than 80 were worst and most of them died. The incidence of impairments after discharge increased in aged patients. We suggest that the age of the patient may be a major factor influencing outcome of cerebellar hemorrhage as well as the level of consciousness on admission and the volume of hematoma.

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Management of ruptured dissecting aneurysm of the vertebral artery (VA-DA) and its surgical indication in the acute stage have remained controversial. The authors have experienced 5 cases of ruptured VA-DA with severe neurological state due to repeat subarachnoid hemorrhage. The outcome was satisfactory in 3 cases operated on by proximal occlusion or trapping in the acute stage. On the other hand, the other 2 cases, treated conservatively, worsened because of vasospasm or rerupture and eventually died. These results suggest that VA-DA cases, even if presenting with severe consciousness disturbance or respiratory dysfunction, should be operated on as early as possible.

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In the present study, we investigated the clinical efficacy of the local fibrinolytic therapy using microcatheter technique and tissue plasminogen activator (t-PA) in 7 patients with basilar artery embolism. Seven cases were treated in the acute stage, within 6 hours of onset. A microcatheter was introduced into the embolus and/or distal to the embolus to keep high concentration of fibrinolytic agent. The t-PA, 5M units/20 ml, was infused continuously through the microcatheter over 20 minutes, and 5 to 15 M units of t-PA was injected. Complete recanalization of the basilar artery was achieved in 5 of 7 patients from 4 to 7.5 hours after onset. Partial recanalization was achieved in 1 patient and recanalization was not achieved in another patient. Three of 5 patients with complete recanalization recovered fully, but 1 died of cerebellar hemorrhagic infarction and brain stem infarction, and the other died following acute cardiac failure. One patient with partial recanalization became severely disabled and an another patient without recanalization died of cerebellar and brain stem infarction. Local fibrinolytic therapy using microcatheter technique and t-PA was effective in patients with basilar artery embolism with a high recanalization rate. The pretreatment neurological state was correlated with the clinical results. Patients with mild to moderate consciousness disturbance or a fluctuating state of consciousness had good recoveries. However, fixed coma state and/or brain stem dysfunction resulted in poor prognoses even if the complete recanalization was achieved within 6 hours.

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