Abnormalities of the vertebrobasilar circulation due to subclavian artery disease.

The studies of Hutchinson and Yates on caroticovertebral stenosis have stimulated further interest in cerebrovascular disease. As a consequence, investigation of the four vessels, supplying the brain is now routine in the assessment of patients being considered for surgery for occlusive disease of the vessels. This has led to some interesting and unexpected findings.The effect of subclavian artery disease on the vertebrobasilar circulation was studied in two patients. Angiography showed the vertebral arteries to function as a collateral pathway when an occlusion of the subclavian artery was present proximal to the origin of the vertebral arteries. In one case both the carotid and the vertebral arteries were implicated in the collateral supply. A normal circulation was restored by subclavian endarterectomy.Studies of other workers have shown that such a circulation may reduce the cerebral blood flow by about 40%, but neither patient described in this report had signs or symptoms of cerebrovascular disease. It is evident that our understanding of the effects of cerebrovascular disease is far from complete.