椎骨動脈閉塞術の施行部位の検討

-正常脳の穿通枝の観察結果より-

抄録

Fifty intracranial vertebral arteries were observed under an operating microscope in order to clarify the originating pattern of small branches. 1) On the average, 3 small branches originated from the intracranial portion of the vertebral artery (VA). Length of the VA distal to PICA origin averaged 16mm. Usually the VA distal to the PICA origin was the main source of such small branches. However, in the case of short distal VA (less than 10mm), more small arteries arose from the VA proximal to the PICA origin.
This finding is clinically useful in determining the occlusion site of to VA for treating unclippable VA aneurysms.
Generally speaking, in order to prevent brain stem ischemia due to occlusion of the VA and its small arteries, the length of the VA distal to the occlusion should be minimized. The occlusion site is influenced by the location of the PICA origin, which is evidenced from a review of previous reports. Based on observation of cadaver brains, it is speculated that, where the VA has a long distal portion, the VA immediately proximal to the PICA origin is the safer site for occlusion to preserve the retrograde blood flow from the contralateral VA at the distal portion where a larger number of the perforators originate.
Where the distal VA portion is short, the VA should be occluded distal to the PICA origin, to preserve blood flow to the proximal portion where more perforators originate.
A VA with no PICA, or on under-developed PICA, may play a major role in blood supply to the brain stem. Therefore, indication of this occluding procedure may be more limited.