A late complication of γ knife radiosurgery.

An 85-year-old man was hospitalized after developing sudden weakness on his right side and mild expressive aphasia. He had undergone γ knife stereotactic radiosurgery to the left thalamus 7.5 years earlier for a disabling essential tremor; the surgery had led to remarkable improvement in his ability to write and use utensils. He was being treated with warfarin for chronic atrial fibrillation. A computed tomography scan of the brain revealed a 2-cm left thalamic hemorrhage in the precise region of the prior thalamotomy.