Kazuo Mizoi

Permissible Temporary Occlusion Time in Aneurysm Surgery as Evaluated by Evoked Potential Monitoring

To clarify the permissible time for temporary vascular occlusion during aneurysm surgery, we have undertaken a retrospective analysis of the results of intraoperative median nerve somatosensory evoked potential (SEP) monitoring in 97 patients with middle cerebral artery (MCA) (46 patients) or internal carotid artery (ICA) (51 patients) aneurysms. All patients underwent temporary vascular occlusion, lasting from 2 to 70 minutes, under the administration of a mixed solution of 20% mannitol with phenytoin and vitamin E. The mean occlusion time was 20.3 minutes for the MCA patients and 15.8 minutes for the ICA patients. The SEP disappeared during occlusion in 42 patients (30 MCA and 12 ICA). All but three eventually recovered the SEP to the baseline level after recirculation, and none of the 39 patients had postoperative sequelae. The time period from the start of occlusion until the complete loss of the SEP averaged 8.6 minutes among these 39 patients, and the occlusion time from total SEP loss until recirculation averaged 12 minutes. In the remaining 3 of the 42 patients (all 3 being ICA aneurysm patients), however, the SEP did not recover after recirculation and all 3 patients showed postoperative sequelae. In two of these three patients, vascular occlusions were performed at the multiple sites (i.e., at the ICA, MCA, anterior cerebral artery, and posterior communicating artery) and the SEP disappeared rapidly after the occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Indirect revascularization for moyamoya disease: Is there a beneficial effect for adult patients?

BACKGROUNDnIt is generally accepted that excellent development of collateral circulation can be achieved through indirect nonanastomotic bypass procedures for pediatric patients with moyamoya disease. However, there are no definitive conclusions about the effect of indirect revascularization for adult patients. To clarify the value of indirect bypass surgery for adult moyamoya disease, we have analyzed their follow-up angiographic results in comparison with those of the pediatric patients.nnnMETHODSnBetween 1989 and 1993, 23 patients underwent combined direct and indirect bypass surgery. They consisted of 16 adults (mean age, 35; range, 20-59) and seven children (mean age, 10; range, 3-16). The main symptoms were those due to cerebral ischemia in all but 1 of 23 patients. Preoperative cerebral blood flow studies showed all patients to have decreased vascular reserve (misery perfusion). Postoperative follow-up angiography was done in all patients at a median of 6 months after the surgery.nnnRESULTSnAll pediatric patients showed good or moderate development of collaterals through the indirect bypass. Among the adult group, seven patients aged 20 to 29 had angiographic results similar to those of the pediatric group . On the other hand, nine patients older than 30 had results contrary to those of pediatric patients: (1) the degree of indirect revascularization declined to moderate or poor grades (especially in patients older than 40) and (2) the degree of direct bypass filling improved to high or medium grades.nnnCONCLUSIONSnThe results suggest that advancing age apparently affects the development of collateral formation through the indirect bypass. Consequently, direct bypass is thought to be the main treatment option for patients older than 40.

How to treat incidental cerebral aneurysms : a review of 139 consecutive cases

BACKGROUNDnTogether with current advances in neuroimaging techniques, the chance of incidental discovery of unruptured cerebral aneurysms has increased and the selection of their appropriate management remains controversial. To provide current data about management results of patients with incidental cerebral aneurysms, we have made a retrospective review of 139 consecutive patients treated either by surgical or conservative means.nnnMETHODSnThe surgical indication for each patient was decided, carefully considering several factors respectively, including the surgical difficulty, aneurysm size, patients age, and medical condition.nnnRESULTSnForty-nine patients were managed conservatively. Eight (16%) of those conservatively managed patients had intracranial hemorrhage due to aneurysm rupture during the follow-up period (mean, 4.3 years). Seven of these eight patients died from a fatal subarachnoid hemorrhage (SAH). The follow-up data showed that the mean size of aneurysms with late hemorrhage was significantly larger than that of aneurysms without subsequent rupture. It was also confirmed that none of the 26 tiny aneurysms smaller than 4 mm in diameter had ruptured. Ninety patients harboring 119 incidental aneurysms less than 25 mm in diameter underwent surgery. There was no surgical mortality or morbidity in this series.nnnCONCLUSIONSnThese excellent surgical results were presumably achieved due to the strict patient selection. In respect to the size of aneurysms, it seems to be justified to recommend surgery for patients with aneurysms larger than 5 mm in diameter.

Clinical and angiographic follow-up of childhood-onset moyamoya disease

To clarify the differences between childhood-onset moyamoya disease and that with onset in adulthood, we studied the clinical course and angiographic findings of adult patients (over 20 years of age) with moyamoya disease of childhood onset (up to 15 years of age). The clinical course in 25 patients could be assessed. The follow-up period was 5–27 years. Neurological deficits were noted in 11/23 and mental disorders in 9/21. In all except one, the illness had started before the age of 7 years. Neither neurological nor mental condition changed during or after adolescence (15–20 years of age). Two patients died of intracranial hemorrhage. The disease progressed in angiographic stage until adolescence, but had stabilized or almost stabilized by the age of 20 years. This study indicates that moyamoya disease with onset in childhood carries high morbidity and mortality. The disease advances in angiographic stage between childhood and adolescence, but stabilizes or almost stabilizes between adolescence and adulthood.

Combined Endovascular and Neurosurgical Approach for Paraclinoid Internal Carotid Artery Aneurysms

The authors review the surgical management of nine complex paraclinoid aneurysms treated with the endovascular balloon catheter technique. With the patient under general anesthesia, the balloon catheter was guided into the feeding artery of the aneurysm by the Seldinger technique. After the aneurysm was exposed, the balloon was inflated temporarily to prevent premature rupture and to facilitate the dissection of the aneurysm. For the larger paraclinoid aneurysm, the double-lumen catheter was introduced into the cervical internal carotid artery (ICA). After temporarily trapping the aneurysm by balloon occlusion of the cervical ICA and clipping the intracranial ICA distal to the aneurysm, retrograde aspiration was performed to collapse the aneurysm. The complete collapse of the large aneurysm by this technique allows an easier dissection of the aneurysm and a safer application of suitable clips. Such a retrograde suction decompression method was used in six large aneurysms. Intraoperative digital subtraction angiography was performed in all cases after the aneurysmal clipping; in three aneurysms, repositioning the clip was required. Only one case of embolic complication was related to the vessel catheterization in this series, which was discovered during the operation. An embolectomy was performed immediately, and there were no postoperative sequelae. We conclude that the combined endovascular and neurosurgical approach, particularly for the large ICA aneurysms, which are difficult to control proximally, can be a useful method of treatment. To prevent complications related to thrombus formation, further refinement in the balloon catheter itself is still needed.

Importance of management of unruptured cerebral aneurysms

BACKGROUNDnSince excellent recovery is hardly expected in patients with severe subarachnoid hemorrhage, management of unruptured aneurysms is essential in reducing the overall mortality and morbidity rates. The widespread use of less invasive imaging tools such as magnetic resonance angiography (MRA) has made Brain Check-up Systems very popular in Japan. Therefore, unruptured aneurysms have been found much more often than before.nnnMETHODSnDuring the 1-year period of 1994, 80 patients underwent radical surgery for aneurysms in our institute. Thirty-two patients (40%) underwent surgery for unruptured aneurysms, while 48 patients (60%) underwent surgery for ruptured aneurysms. In patients with unruptured aneurysms, we have operated when the aneurysm is larger than approximately 5 mm in diameter, arising from the common sites in the circle of Willis, and when the patients age is under 70 years. To prevent surgical complications in unruptured aneurysms, we often use a wrapping technique with Bemsheets (cotton) and adhesives.nnnRESULTSnThe outcomes were good in all 32 cases of unruptured aneurysms.nnnCONCLUSIONSnWe believe that early detection and prophylactic surgery for unruptured aneurysms will improve the overall outcome of aneurysm treatment in the future.

Enterogenous cyst at the cerebellopontine angle: case report.

A case of enterogenous cyst at the cerebellopontine (CP) angle is reported. A review of the literature yielded only seven cases of intracranial enterogenous cysts, and our case is the first one arising at the CP angle. The histological features, pathogenesis, and radiological and auditory brain stem response findings are discussed.

Protective effect of phenytoin and its enhanced action by combined administration with mannitol and vitamin E in cerebral ischaemia.

SummaryTo study the therapeutic effect of phenytoin on cerebral ischaemia and confirm whether or not the effectiveness of phenytoin could be enhanced by combined administration with free radical scavengers, twenty-five dogs were subjected to ischaemia, using the “canine model of the completely ischaemic brain regulated with a perfusion method”. Five animals served as untreated controls, fifteen received treatment with several doses of phenytoin and five were treated with 10mg/kg phenytoin, 2g/kg mannitol and 30mg/kg vitamin E. These drugs were administered prior to the production of ischaemia. After one hour ischaemia, cerebral blood flow was restored and the recovery of electrical activity of the brain and the degree of brain swelling were observed for three hours.With regard to the recovery of the EEG, the higher the administered dosage, the better was the degree of recovery of the EEG. And the group which was treated with a combination of phenytoin, mannitol and vitamin E exhibited remarkable recovery of the EEG. With regard to the degree of brain swelling, a similar doserelated suppressive effect was seen in the phenytoin-treated groups. Furthermore, in the combination therapy group, brain swelling was attenuated significantly.Based on these results, it is concluded that phenytoin has a protective effect in cerebral ischaemia and it shows its most remarkable effect when given together with radical scavengers, such as mannitol and vitamin E.

The protective effect of vitamin E on cerebral ischemia

Using the canine model of the completely ischemic brain regulated with a perfusion method, the effects on cerebral ischemia of vitamin E, which is known to act as an antioxidant, were investigated. After pretreatment with vitamin E by oral or intravenous administration, cerebral blood flow was reduced to 1/10th the normal state and, 1 hour later, allowed to return to normal. Subsequent changes in electrical activity were observed, and the effects of vitamin E were evaluated. In the control group, no recovery of electrical activity was seen. In the groups given vitamin E, the recovery time was significantly shortened in the dogs given 30 mg/kg of vitamin E intravenously. Furthermore, in the groups treated with vitamin E, distinct recovery of electroencephalographic potentials at 3 hours after recirculation was apparent. These effects were more favorable in the case of intravenous administration than in the case of oral administration. These experimental results indicate that the administration of vitamin E is effective in protecting the brain from cerebral ischemia.

Experimental study of new cerebral protective substances — functional recovery of severe, incomplete ischaemic brain lesions pretreated with mannitol and fluorocarbon emulsion

SummaryUsing the “canine model of complete ischemic brain regulated with a perfusion method” in which it is possible to control the degree of blood flow to a cerebral hemisphere via a perfusion pump, the effects of mannitol (which acts as a free radical scavenger) and fluorcarbon emulsion (FC) (which has 0.1 μm of average particle size and a high oxygen-carrying capacity) on cerebral ischaemia were investigated. After pretreatment with the drugs, blood flow was reduced via the pump to 1/10 the normal state and 1 hour later, return to a normal state allowed. Subsequent changes in electrical activity were observed and the effects of the drugs evaluated.In the control group, no recovery of electrical activity was seen, but in the animals treated with either mannitol or FC, incomplete, yet distinct recovery was apparent. In the animals administered mannitol together with FC, however, marked recovery was evident.These experimental results indicate that the combined administration of mannitol and FC is effective in protecting the brain from cerebral ischaemia.