Abstract
The effect of the change in cerebrovascular reactivity (CVR) in each brain area on cognitive function after extracranial-intracranial bypass (EC-IC bypass) was examined. Eighteen patients who underwent EC-IC bypass for severe unilateral steno-occlusive disease were included. Single-photon emission CT (SPECT) for evaluating CVR and the visual cancellation (VC) task were performed before and after surgery. The accuracy of VC was expressed by the arithmetic mean of the age-matched correct answer rate and the accurate answer rate, and the averages of the time (time score) and accuracy (accuracy score) of the four VC subtests were used. The speed of VC tended to be slower, whereas accuracy was maintained before surgery. The EC-IC bypass improved CVR mainly in the cerebral hemisphere on the surgical side. On bivariate analysis, when CVR increased post-operatively, accuracy improved on both surgical sides, but the time score was faster on the left and slower on the right surgical side. Stepwise multiple regression analysis showed that the number of the brain regions associated with the time score was 5 and that associated with the accuracy score was 4. In the hemodynamically ischemic brain, processing speed might be adjusted so that accuracy would be maintained based on the speed-accuracy trade-off mechanism that may become engaged separately in the left and right cerebral hemispheres when performing VC. When considering the treatment for hemodynamic ischemia, the relationship between CVR change and the speed-accuracy trade-off in each brain region should be considered.
Highlights
Symptomatic major cerebral arterial occlusion or stenosis makes the status of cerebral hemodynamics progress from stage 0 to stage 1 hemodynamic ischemia (autoregulatory vasodilation to keep cerebral blood flow (CBF) normal) and stage 2 hemodynamic ischemia (CBF cannot be maintained, and brain tissues increase the oxygen extraction fraction (OEF)) as the stenosis progresses, and cerebral infarction becomes inevitable before long [1,2,3,4]
According to a Japanese Extracranial-Intracranial Bypass Trial (JET) study, if rest CBF was less than 80% of the normal value and cerebrovascular reactivity (CVR) was less than 10%, EC-IC bypass surgery was more effective in preventing cerebral infarction than drug therapy [5, 6]
According to the JET study, EC-IC bypass was indicated for regional CBF (rCBF) reduction of less than 80% and regional CVR reduction of less than 10% [5, 6]
Summary
Symptomatic major cerebral arterial occlusion or stenosis makes the status of cerebral hemodynamics progress from stage 0 (normal cerebral hemodynamics) to stage 1 hemodynamic ischemia (stage 1) (autoregulatory vasodilation to keep cerebral blood flow (CBF) normal) and stage 2 hemodynamic ischemia (stage 2) (CBF cannot be maintained, and brain tissues increase the oxygen extraction fraction (OEF)) as the stenosis progresses, and cerebral infarction becomes inevitable before long [1,2,3,4]. To prevent progression from stage 2 to cerebral infarction, extracranial-intracranial (EC-IC) bypass surgery has been considered [5,6,7]. One of the key issues lies in how to evaluate stage 2, especially the signs of progression to cerebral infarction. Positron emission tomography (PET) has the advantage of being able to diagnose stage 2 because OEF can be measured [4], its clinical availability is limited by its high cost and complexity [2]. According to a Japanese Extracranial-Intracranial Bypass Trial (JET) study, if rest CBF was less than 80% of the normal value and CVR was less than 10%, EC-IC bypass surgery was more effective in preventing cerebral infarction than drug therapy [5, 6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
