[A case of transtentorial upward herniation due to cerebellar infarction manifesting upward gaze palsy as an initial sign].

Transtentorial upward herniation is a rare complication of cerebellar infarction and its development indicates an emergency and necessity of posterior cranial fossa decompression. A 63-year-old man with a history of myocardial infarction was admitted to the hospital complaining of sudden onset of vertigo and headache. Neurological examination revealed marked upward gaze palsy, right blepharoptosis, facial weakness, hearing loss on the left side and ataxia of the left upper and lower extremities. A few hours later, he rapidly lost consciousness and MRI revealed massive infarction in the left cerebellar hemisphere and transtentorial upward herniation. Immediate surgical decompression of the posterior cranial fossa was performed, thereafter patient gradually improved. This case suggests that upward gaze palsy is an important initial sign of transtentorial upward herniation with massive cerebellar infarction.