Kernohan-Woltman Notch Phenomenon: A Case of Paradoxical Hemiparesis

The Kernohan-Woltman phenomenon, a rare and often misunderstood neurological condition, is recognized as a false localizing neurological sign. This phenomenon is characterized by a motor deficit ipsilateral to the site of the neurological lesion and occurs due to the mass effect of supratentorial lesions causing a shift of midline structures and subsequent transtentorial herniation, leading to compression of the contralateral corticospinal (pyramidal) fibers within the cerebellum, ipsilateral to the lesion. This case describes a patient with human immunodeficiency virus-1 and chronic kidney disease who presented to the emergency department with uremic syndrome and a hypertensive crisis. She experienced sudden neurological deterioration, manifesting as prostration, anisocoria, and left hemiparesis, in the context of an acute subdural hematoma of the left cerebral hemisphere, which is a rare complication of hypertensive crisis. The fact that the hemiparesis was on the same side as the hematoma indicates a rare neurological sign, known as the Kernohan-Woltman phenomenon. This case is particularly noteworthy due to the rare coexistence of these conditions and the atypical presentation of neurological symptoms in the context of supratentorial lesions. The case emphasizes the importance of recognizing this phenomenon in patients with mass-effect lesions, especially in the setting of critical illness, as early identification can influence clinical decision-making and management strategies. Given the rarity of this phenomenon, this report contributes to the literature by providing insight into its clinical presentation and diagnostic challenges, highlighting its relevance in neurocritical care.