11. The cerebrovascular system

The cerebrum is supplied both by the carotid arteries and the vertebral arteries (which unite to form the basilar artery). These three blood vessels are connected by a properly developed circle of Willis, so that if one fails the others can take over to a degree. Basilar artery occlusion leads inevitably to major neurological symptoms and signs, however, since the brainstem is deprived of oxygenated blood. Regulation of the cerebral vascular system is autonomous of the rest of the body, so that a fall in blood pressure does not immediately affect the cerebrum. If cerebral perfusion is impaired, infarction can occur. That gives rise to various syndromes, depending on which region is affected. Blood vessel abnormalities in the form of aneurysms, arteriovenous malformations, dissection and a number of less common problems lead to neurological conditions and potentially to serious disability. Diagnosis is based on CT, MRI, intra-arterial contrast angiography and/or duplex scanning.