Spatial relations of dorsal anastomoses and lesion border after middle cerebral artery occlusion

Occlusion of the middle cerebral artery invariably results in infarction of tissue in stroke-prone spontaneously hypertensive rats (SHRSP). To determine if the lesion border extends beyond the territory of the occluded middle cerebral artery or if the lesion enlarges with time after the occlusion, spatial relations of the lesion and the primary anastomosing collateral branches were investigated. Measurements were made 1 day (n = 8) or 21 days (n = 8) after occlusion in 5-8-week-old SHRSP brains marked by triphenyltetrazolium chloride (TTC) or tissue atrophy. After 1 day of occlusion, the border between TTC-marked and -unmarked tissue was parallel to, and without spatial displacement from, the medial border of infarcted tissue measured 21 days after the occlusion. Thus, the TTC border accurately localizes the medial border of ischemic tissue that progresses to atrophy. The lesion border was 1.16 +/- 0.04 mm downstream from the anastomoses, and the mean distance was not significantly different in frontal, parietal, or rostral occipital regions or between the 2 groups of rats. Thus, a small but significant amount of tissue between the anastomoses and the lesion border was protected against infarction after middle cerebral artery occlusion in SHRSP. After 21 days of occlusion, the dorsal anastomoses were enlarged, bilaterally symmetric in position but not size, and without displacement from the anastomoses in 1-Day rats. Large-diameter anastomoses were further from the lesion than small-diameter anastomoses in both groups of rats, thus indicating that protection is greater near large anastomoses than near small ones.(ABSTRACT TRUNCATED AT 250 WORDS)