Kernohan Woltman notch phenomenon caused by subdural chronic hematoma: Systematic review and an illustrative case.

Kernohan Woltman Notch Phenomenon (KWNP) is caused by a supratentorial lesion pressing the contralateral cerebral peduncle against the free edge of the tentorium of the cerebellum. It is manifested by neurological signs of ipsilateral localization; cerebral MRI is the most sensitive examination for KWNP. Our patient is a 50-year-old woman, operated in 2011 for aortic and mitral valve replacement by mechanical prosthesis, under oral anticoagulant, consults for headaches evolving for 20 days without any notion of head trauma with installation of a progressively worsening left hemibody deficit. Glasgow coma scale was 14 (E3 V5 M6) with left anisocoria 4mm left/2mm right with left hemiplegia. CT shows a chronic left hemispheric subdural hematoma 13.5mm thick with subfalcorial and ipsilateral temporal involvement of the deficit. The cardiovascular examination as well as the biological assessment was unremarkable. The patient was operated on with a total recovery in 12 days, the anticoagulant is resumed on day 20 postoperatively, with close monitoring. KWNP may contribute to misdiagnosis in patients with bilateral corticospinal tract lesions, and anticoagulation poses a problem in stopping and restarting treatment due to the risk of bleeding on one side and thrombosis on the other side.