対側内頚動脈狭窄を伴う慢性内頚動脈閉塞の治療方針の検討

Strategy for Revascularization of Chronic Carotid Occlusion with Contralateral Carotid Stenosis

Ⅰ．背景および目的

　内頚動脈や中大脳動脈など，頭蓋内外の主幹動脈の高度狭窄によりその動脈の灌流域の脳血流が低下している場合，また前交通動脈や後交通動脈などWillis動脈輪を介する側副血行路や脳軟膜吻合などを介する側副血行路，あるいは外頚動脈からの吻合が良好に発達している場合には脳血流が保たれるが，側副血行路の発達が不十分な場合は血圧の変動や脱水などにより血行力学的な脳梗塞が起こることがある．

　一側の内頚動脈が閉塞し，急性期に広範な脳梗塞を免れている場合，同側の大脳半球の血流は一般に対側内頚動脈からの前交通動脈を介した血流や，後方循環からの側副血行路で賄われている．この状態に加え，対側の内頚動脈に狭窄を来した場合，内頚動脈閉塞側の大脳半球に血流低下を伴う危険性がある．

　Background and Purpose: The optimal therapeutic approach for chronic carotid occlusion with contralateral carotid stenosis (ICO-ICS) remains uncertain. The aim of this study was to elucidate the safety and efficacy of initial vascular reconstruction for ICS in patients with ICO-ICS.

　Patients and Methods: Eleven patients with ICO-ICS who demonstrated severe cerebral hypoperfusion in the hemisphere ipsilateral to ICO were treated in our institution between February 2003 and November 2007. Revascularization for ICS after measuring cerebral blood flow (CBF) by single photon emission computed tomography (SPECT) was performed either by carotid endarterectomy or carotid stenting. External carotid artery-internal carotid artery (EC-IC) bypass for ICO was also performed when SPECT after revascularization for ICS still demonstrated marked hypoperfusion.

　Results: In 6 patients with collateral flow via the anterior communicating artery and/or who had high-grade ICS (＞70%), sufficient improvement of CBF solely by revascularization for ICS was confirmed. With regard to perioperative complications, 2 patients suffered bradycardia and hypotension and another 2 showed asymptomatic cerebral infarction on diffusion-weighted magnetic resonance imaging.

　Conclusions: Overall results for revascularization of ICS prior to that for ICO in patients with ICO-ICS were acceptable. CBF of bilateral hemispheres was sufficiently improved in more than half of the patients solely by revascularization for ICS. This strategy might be both efficient and effective for ICO-ICS.