Delayed Hemiparkinsonism Associated with Kernohan's Notch in a Patient with a Ruptured Arteriovenous Malformation.

A 24-year-old female patient was admitted for a right frontal intracranial hematoma with an uncal herniation due to a ruptured arteriovenous malformation and therefore underwent emergency surgery. Neuroimaging revealed left-sided midbrain notching against the tentorium, indicating Kernohan's notch phenomenon. She denied experiencing any short-term neurological deficits but right-sided delayed hemiparkinsonism developed 18 months later. Dopamine transporter tracer uptake was severely reduced in the left striatum, suggesting nigrostriatal degeneration secondary to Kernohan's notch. Uncal herniations are potentially fatal, but surgery can save the patient's life and improve the functional outcomes. Clinicians should therefore be aware of delayed hemiparkinsonism as a rare complication of Kernohan's notch phenomenon.