Yoshikazu Iwata

Therapeutic occlusion of the vertebral artery for unclippable vertebral aneurysm: relationship between site of occlusion and clinical outcome.

Six cases of unclippable vertebral aneurysms were treated by therapeutic occlusion of the proximal vertebral artery. In three cases, the vertebral artery was clipped proximal to the posterior inferior cerebellar artery (PICA), and all of these patients had a postoperative embolic complication or a fatal subarachnoid hemorrhage. In two cases, the vertebral artery was clipped distal to the PICA and in one case the PICA was absent and the vertebral artery was clipped proximal to the aneurysm. All three of these patients did well without any neurological deficit. Possible mechanisms of the complications are discussed, and the importance of not clipping the PICA is stressed.

Effect of brain-stem lesions on metrazol-induced seizures in cats

Abstract 1. 1. The chronic effect of bilaterally paired lesions in the cats brain-stem on Metrazol-induced seizures was studied in order to clarify the intracerebral mechanism for the maintenance of epileptic excitability. 2. 2. The results seem to indicate that there are two systems of facilitatory and inhibitory functions in the brain-stem rostral to the pons as far as Metrazol-induced seizure activity is concerned. The facilitatory system consists of the caudal mesencephalon extending rostrally to the posterior hypothalamus through the ventral part of the rostral mesencephalon and posterior sub-thalamus, and also of the medio-dorsal nucleus of the thalamus. the inhibitory system consists of the dorsal part of the rostral mesencephalon extending rostrally to the thalamus and also of the anterior hypothalamus. 3. 3. It may be suggested that this facilitatory system plays a significant role in the onset and generalization of the Metrazol seizure.

Improvement of cerebral blood flow and/or CO2 reactivity after superficial temporal artery-middle cerebral artery bypass in patients with transient ischemic attacks and watershed-zone infarctions

The effect of extracranial-intracranial bypass anastomosis on cerebral blood flow and CO2 reactivity during hypocapnia was investigated in ten patients with transient ischemic attacks or watershed infarctions due to carotid occlusive diseases. Six patients had occlusion and four had stenosis (greater than 50%) of the internal carotid artery. Those with infarctions had increased cerebral blood flow and CO2 reactivity postoperatively, and improved clinically. Those with transient ischemic attacks due to stenosis (greater than 50%) of the internal carotid artery had increased CO2 reactivity postoperatively but constant normal regional blood flow. Cerebral blood flow improved in those with poorer flow, CO2 reactivity increased in those with better reactivity, and better CO2 reactivity preoperatively brought about a greater flow increase. The pre- and postoperative evaluation of cerebral blood flow and CO2 reactivity is believed to be useful in evaluating the effectiveness of bypass anastomosis. Preoperative evaluation might be informative in selecting candidates for bypass.

Ultrasonic Doppler Studies after Superficial Temporal-Middle Cerebral Artery Anastomosis:

The ultrasonic Doppler technique was applied to evaluate the effect of STA-MCA anastomosis. Not only the STA itself, but also ophthalmic and major aortocranial arteries were recorded by the Doppler technique in 12 patients who had undergone STA-MCA anastomosis for internal carotid artery occlusion or stenosis. The examination was performed before, and within a month after the operation. The blood flow pattern of the STA, which had had an external carotid flow pattern, was altered to an internal carotid flow pattern by the STA-MCA bypass operation. The findings of Doppler sonograms of the STA were exactly consistent with post-operative angiograms and precisely represented the bypass patency. Among 7 patients with reverse flow direction in the ophthalmic artery before the operation, the reverse flow had decreased in 5 patients post-operatively. But no remarkable change in the ophthalmic artery was detected in the remaining 2 patients. The blood flow velocity patterns of major aortocranial arteries showed no change post-operatively.

Combined Common Carotid Ligation and Axillary-middle Cerebral Artery Interposed Long Saphenous Vein Bypass Graft for Treatment of Unclippable Giant Internal Carotid Aneurysm

Recently combined ligation of ICA and STA-MCA anastomosis has become the treatment of choice for unclippable giant aneurysms of the ICA . However, ischemic complications have been reported in 10-25% of the cases that underwent this procedure, because of the limited flow provided by the STA-MCA bypass and of thrombo-embolic ischemia originating from the stump of the occluded ICA and thrombosing aneurysm. An interposed long saphenous vein bypass graft was utilized between the axillary artery and the angular branch of the middle cerebral artery instead of STA-MCA anastomosis to treat a patient with an unclippable giant aneurysm of the cavernous portion of the right ICA combined with acute ligation of CCA. Ten minute manual compression of the right CCA developed neither abnormality of EEG nor ischemic symptoms. Angiography also demonstrated a good cross-filling of the ipsilateral carotid region. However, a SPECT subtraction study revealed 70% reduction of flow in the ipsilateral MCA region by manual compression of the right carotid artery. Intraoperative measurement of the flow through the vein graft was 80 ml/min. CCA ligated acutely on the third postoperative day after the patency of the vein graft bypass was assured . A postoperative angiogram revealed that the giant aneurysm was thrombosed successfully . There was a good filling of the left MCA territory through the graft and ACA through the anterior communicating artery from the contralateral circulation. Thus the ICA giant aneurysm was isolated, trapped and thrombosed . The postoperative SPECT study revealed a normal CBF at rest in both hemispheres . By compressing the vein graft bypass, 60% reduction of CBF in the MCA territory was demonstrated in the subtraction image of the SPECT. A three year follow-up revealed good patency of the vein graft with no ischemic symptoms. Acute ligation of CCA provides less chance of emboly, and a vein graft bypass from the axillary artery can provide an immediate postoperative high flow without carrying thrombi from the ICA stump. The giant aneurysm of the intracranial ICA is isolated from ipsilateral cerebral circulation . Thus, both hemodynamic and thrombo-embolic ischemia can be avoided. Kevwords: