CEREBRAL-DAMAGE CAUSED BY INTERRUPTED, REPEATED ARTERIAL-OCCLUSION VERSUS UNINTERRUPTED OCCLUSION IN A FOCAL ISCHEMIC MODEL

Temporary intracranial arterial occlusion is often utilized during the surgical treatment of intracranial aneurysms. Although numerous exper imental studies have suggested that repetitive, brief periods of globa l ischemia cause more severe cerebral injury than a similar single per iod of global ischemia, this issue has not been extensively studied in relation to focal ischemia. It remains controversial whether it is sa fer to use brief periods of interrupted, temporary occlusion separated by reperfusion periods, or a more prolonged, single temporary occlusi on. This question is addressed in studies on a rabbit model of transie nt, focal cerebral ischemia. Sixteen anesthetized rabbits underwent tr ansorbital occlusion of the left internal carotid, middle cerebral, an d anterior cerebral arteries, with one of two paradigms: uninterrupted occlusion (1 hour of temporary occlusion followed by 5 hours of reper fusion in eight rabbits), or interrupted occlusion (three separate 20- minute periods of occlusion, with 10 minutes of reperfusion between oc clusions, followed by 4 hours, 40 minutes of reperfusion in eight rabb its). Histopathological evaluation for ischemic neuronal damage and ma gnetic resonance imaging studies for ischemic edema were conducted 6 h ours after the initial arterial occlusion. The animals in the interrup ted, repeated occlusion group showed a 59% decrease in the area of cor tical ischemic neuronal damage (mean +/- standard error of the mean 10 .0% +/- 1.7%) compared with the uninterrupted occlusion group (24.4% /- 5%, p = 0.016). There was no difference between the groups in the e xtent of striatal ischemic damage or area of ischemic edema. These res ults suggest that interrupted, repeated focal ischemia causes less cor tical ischemic injury than uninterrupted transient ischemia of a simil ar total duration. Although caution should be exercised in extrapolati ng from these results to the clinical situation, they may have importa nt implications for temporary arterial occlusion during intracranial s urgery.