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III. Ischemic Disorders

A. Introduction

Ischemia, the failure of cerebral blood flow to a region, results in infarction (complete necrosis). The most common cerebrovascular lesions are ischemic in nature – about 85% of "strokes" are due to thrombosis or occlusive vascular disease. The vasculature that leads from the heart to the brain is the most common location of occlusive disease. The site of infarction and resulting clinical signs depend on many factors in addition to the site of occlusion, including  

  • extent of collateral circulation,
  • presence of anomalies,
  • magnitude and suddenness of occlusion, and
  • duration of ischemia.

For example, when occlusion of the internal carotid artery occurs, the infarction is most commonly in the distribution of the middle cerebral artery because the area supplied by the anterior cerebral artery receives blood via the anterior communicating artery.  

Transient Ischemic Attacks (TIAs) can serve as a warning of possible impending stroke. These are transient with no permanent deficits or pathology.