uncal herniation
Pronunciation: UN-kal her-nee-AY-shun
Downward displacement of the uncus through the tentorial notch, causing brainstem compression.
Full Definition
Uncal herniation occurs when increased intracranial pressure forces the medial portion of the temporal lobe (uncus) downward through the tentorial notch. This displacement compresses the third cranial nerve and brainstem structures, leading to characteristic clinical signs including ipsilateral pupil dilation, contralateral hemiparesis, and altered consciousness. Uncal herniation is a life-threatening condition that requires immediate medical intervention. In neurocritical care documentation, this term must be used precisely to distinguish it from other herniation syndromes such as central or subfalcine herniation.
Usage
Usage note: Do not use generically for all brain herniation types. Specify anatomical location and direction of displacement.
In Context
- "Clinical examination revealed signs consistent with uncal herniation, including a fixed and dilated left pupil." — neurology consultation note
- "Emergency imaging was ordered to evaluate for uncal herniation given the patient's rapidly declining neurological status." — emergency department note