Uncal Herniation

Excerpt

The uncus is a structure at the anterior medial aspect of the parahippocampal gyrus in the medial temporal region of the brain. The medial temporal region is within the supratentorial compartment of the cranium connected to the subtentorial compartment via the tentorium cerebelli through the tentorial notch. The structures in the tentorial notch include the midbrain, third cranial nerve, posterior cerebral arteries, and superior cerebellar arteries. The cerebellum occupies the posterior portion of the tentorial notch. Uncal herniation occurs when rising intracranial pressure causes portions of the brain to flow from one intracranial compartment to another; this is a life-threatening neurological emergency and indicates the failure of all adaptive mechanisms for intracranial compliance.