EC-IC Bypassにより脳虚血の再発は予防できるか？

Can EC-IC Bypass Prevent Brain Ischemia from Recurring?

I．はじめに

　EC-IC bypassの虚血性血管障害に対する有効性は1985年のEC-IC bypass cooperative studyにて内科的治療に勝るものではないという結論になった^17）．しかしその後もhemodynamic strokeなど，ある特定のsubgroupに関してはEC-ICbypassの適応があると言われて久しい．しかし，先日日本で行われた多施設共同研究でも，脳血流量の低下が証明された症例に限定されていても，EC-IC bypassの有効性は証明されなかった^12）．

　Hemodynamic strokeでは理論的にはEC-ICbypassにより，ischemic strokeの再発は予防できるはずである．確かにEC-IC bypassが脳血流検査にてhemodynamic compromiseを改善することは確実であり，われわれの研究でもその結果は支持されている^6,10）．しかし，hemodynamiccompromiseが存在することをSPECTなどの方法で証明できた場合でも，ischemic strokeの再発はhemodynamicな要因のみで起こるものではなく，穿通枝の障害や，血栓塞栓症の関与などでも起こりうるため，必ずしも脳梗塞の再発を完全に予防できるものではないことは明らかなことである．

The effectiveness of extracranial-intracranial arterial bypass (EC-IC bypass) surgery for patients withhemodynamic compromise still remains controversial. In the present study, we evaluated the correlationbetween the pre- and post-surgical cerebral hemodynamics and long-term prognosis.

28 patients and a subsequent 21 patients (41 men, eight women: mean age 59.9 [S.D. 8.6] years) with re-duced cerebrovascular reserve due to steno-occlusive disease of the cerebral major arteries formed thestudy groups 1 and 2, respectively. Measurement of the mean hemispheric cerebral blood flow (mCBF)and the cerebral vasoreactivity (%mCVR) with an intravenous acetazolamide injection were performed bya ¹³³Xe inhalation method and SPECT. Patients were treated with EC-IC bypass surgery and measurementof mCBF and %mCVR were made again about one month after surgery. The patients were observed for along period (mean 44.3 months).

During the follow-up period, 6 patients experienced recurrent ischemic strokes. The annual incidence ofrecurrent ischemic stroke was 4.4%. The patients with significantly reduced pre- and post-surgical restingmCBF of the affected hemisphere were at significantly higher risk of recurrent ischemic stroke than thepatients with normal mCBF (p＜0.01). The %mCVR of the affected hemisphere rose after surgery.