The cerebral metabolic rate of oxygen consumption (CMRO2) arises from neurons utilizing energy for two functions:

1) maintenance of cell integrity (homeostasis) which normally accounts for ≈ 40% of energy consumption, and 2) conduction of electrical impulses. The occlusion of an artery produces a central core of ischemic tissue where the CMRO2 is not met. The oxygen deficiency precludes aerobic glycolysis and oxidative phosphorylation. ATP production declines and cell homeostasis cannot be maintained, and within minutes irreversible cell death occurs; a so-called cerebral infarction. Surrounding this central core is the penumbra, where collateral flow (usually through leptomeningeal vessels) provides marginal oxygenation which may impair cellular function without immediate irreversible damage. Cells in the penumbra may remain viable for hours.

Cerebral ischemia due to cerebral vasospasm is a feared complication in patients following aneurysmal subarachnoid hemorrhage (SAH).

see Posttraumatic cerebral infarction.

see Malignant middle cerebral artery infarction.

Brain infarction results from a focal decrease in cerebral blood flow.

A tandem occlusion is an uncommon presentation of acute ischemic stroke that involves occlusion of the extracranial internal carotid artery (EICA) and concomitant occlusion of either the intracranial ICA and/or middle cerebral artery