Extracranial-intracranial bypass in experimental cerebral infarction in dogs.

Unilateral permanent occlusion of the proximal part of the middle cerebral artery (MCA) was performed in 24 dogs. End-to-side anastomosis of the maxillary artery (MA) and a branch of the MCA on the occluded side was made 4 hours later in 8 dogs (prompt bypass group), and 3 weeks later in 5 dogs (delayed bypass group) using an operating microscope. The other 11 dogs without MA/MCA anastomosis were used as controls. A common carotid angiogram of control animals was done 2 to 5 weeks after the occlusion, and a selective external carotid angiogram of animals with an anastomosis was done 2 weeks after making an MA/MCA anastomosis. When the animals were killed, transcarotid perfusion was carried out, and the brains examined histologically. Eight of the 11 control animals showed mild to severe neurological defects, the other 3 died. In contrast, animals with patent bypass grafts, made soon after the MCA occlusion, showed no neurological defects. Examination of the brains of control dogs showed that permanent occlusion caused medium to large infarcts in the territory supplied by the occluded MCA. Of the 8 dogs in the prompt bypass group, only 1 had an occluded bypass, and among the 7 dogs with a patent prompt bypass, 1 had no infarct and 6 had small infarcts detected microscopically. In the group with a patent delayed bypass, the clinical features were similar to those of the controls, but on postmortem examination the infarcts were found to be smaller than those in control animals. No hemorrhagic infarcts were found in either the prompt or delayed bypass group. Results suggest that re-establishment of blood flow by construction of an extracranial-intracranial bypass, particularly if done soon after MCA occlusion, may be valuable for restoring neurological functions without causing appreciable pathological damage to the brain.