TIA症例における脳血流量とCO2反応性

Cerebral Blood Flow and CO2 Reactivity in Patients with Transient Ischemic Attack

要旨　慢性期TIA症例における脳循環動態を明らかにする目的で，TIA症例10例および健康成人5例（control）において，¹³³Xe吸入法を用いて，安静時ならびに5％CO2負荷時の脳血流測定を行った。脳血流量の指標として，Initial Slope Index（ISI）を用い，安静時ならびに負荷時の半球平均値meanISI，CO2反応性について検討した。安静時meanISIは，controlに比べTIA症例において，病側・健側の両半球で有意に低下していた（p＜0.05）。5％CO₂負荷により，TIA症例のmeanISIは，両半球で有意に増加したが，負荷時meanlSIも両半球において，controlに比べ有意に低下していた（p＜0.05）。TIA症例のCO₂反応性は，con—trolに比べ，両半球においてやや低下していたが，その差は有意でなかった。TIA症例において，脳血管のCO₂反応性は健康成人と同程度に保たれているが，慢性的に広汎な脳乏血が存在し，この上に，microem—bolusやhemodynamic compromiseなどによる一過性の局所脳血流低下が加わり，TIAが発症すると考えられた。

　To elucidate the changes in cerebral blood flow (CBF) and CO₂ reactivity in patients with transient ischemic attack (TIA), 10 patients with TIA and 5 healthy adults (controls) underwent two consecutive CBF measurements (i. e. the first measurement during room air inhalation and the second measurement during 5%CO₂ inhalation) .Hemispheric mean CBF was determined by each CBF measurement using ¹³³Xenon inhalation method. CO₂ reactivity was evaluated by analysing ⊿CBF ( = mean CBF during hypercapnea-mean CBF at rest) and ⊿CBF/⊿PaCO₂ . The resting mean CBF values in the bilateral hemispheres (i. e. both of the affected and unaffected hemispheres) were significantly lower in TIA patients than controls (p＜0.05). Inhalation of 5%CO₂ significantly increased mean CBF in TIA patients bilaterally, however the mean CBF value during hypercapnea was again significantly lower in TIA patients than controls (p＜0.05). CO₂ reactivity in TIA patients was not significantly different from controls (p>O. 05). The result demonstrated that TIA patients have a chronic and global cerebral oligemia with normal CO₂ reactivity. The chronic and global cerebral oligemia may develop a transient ischemic neurological symptom by being superimposed with local decrease of CBF.