A 30-year-old driver was involved in a car accident. Examination revealed left scalp swelling and left hemiparesis including the face. Posttraumatic Kernohan notch phenomenon typically refers to a subdural hematoma resulting in delayed ipsilateral hemiparesis.1 Evolving uncal herniation through the tentorial incisura displaces the cerebral peduncle against the contralateral rigid tentorium, producing this false localizing sign.
In this case, imaging (figure) showed lateralized temporal lobe microhemorrhages under the site of head impact with splenial hemorrhage and a contralateral cerebral peduncular lesion suggesting recoil of the brain against the immobile falx cerebri and contralateral tentorium resulting in a contusional Kernohan notch phenomenon.
Figure. Axial brain MRI slices.
Diffusion-weighted image reveals a right peduncular lesion (A, arrow). Susceptibility-weighted images show contusional microhemorrhages under the site of head trauma (B, circle) and a splenial hemorrhage (C, arrowhead).
AUTHOR CONTRIBUTIONS
Designed the concept, analyzed data, and wrote the clinical summary.
STUDY FUNDING
No targeted funding reported.
DISCLOSURES
The author reports no disclosures. Full disclosure form information provided by the author is available with the full text of this article at Neurology.org/cp
REFERENCE
- 1.Kernohan J, Woltman H. Incisura of the crus due to contralateral brain tumour. Arch Neurol Psychiatry 1929;21:274–287. [Google Scholar]