[Changes in CBF pattern after bypass surgery studied by CT with Xe enhancement]

Using a new method for rCBF measurement by serial CT scanning with non-radioactive xenon enhancement, CBF was measured before and/or after microsurgical anastomosis in five cases of focal cerebral ischemia.

Studies were carried out on 2 cases of MCA occlusion, 2 of IC occlusion, and 1 of "Moyamoya" disease. CBF was measured both before and after surgery in 4 cases, and the remaining case was measured after anastomosis. Pre-operative CBF was measured 1.4 +/- 0.5 months after the onset and post-operative CBF was 2 +/- 1 months after surgery. While 50 to 70% non-radioactive xenon was inhaled for 25 min and then discontinued, serial CT scanning was carried out every 3 min. K-map (clearance rate), lambda-map (partition coefficient), and CBF-map were displayed on CRT as images of each value.

In all cases, initial pre-operative CBF decreased not only in the ipsilateral hemisphere, but also in the contralateral hemisphere. Especially in the major stroke cases, CBF reduction in the low density areas seen in CT was more than 75% of normal values. After microsurgical anastomosis, CBF increased in both hemispheres. In two cases of reversible ischemic attacks without any change in CT, the CBF markedly increased in central areas of ischemia and the CBF values became higher than normal value, that is hyperemia. On the contrary, in the central areas of the major stroke cases, that is, the low density areas in CT, CBF was still very low (under 25% of normal value) after anastomosis. However, in these cases, marked hyperemia was seen in the surrounding area of ischemic focus.