A 62-year-old man underwent percutaneous balloon catheter compression of the gasserian ganglion for typical trigeminal neuralgia. After this, a subarachnoid hemorrhage was discovered and normal pressure hydrocephalus developed, which required shunting. Although the neurological function recovered, the patient died 8 months later because of supervening hepatic insufficiency, probably caused by protracted antibiotic therapy. Such a fatal complication, the first one associated with the technique of percutaneous trigeminal compression, was perhaps predisposed by preexistent cerebral atrophy with enlargement of the subarachnoid spaces; the unforeseen piercing of the dilated trigeminal cistern probably permitted the intracranial subarachnoid diffusion of an otherwise trivial hemorrhage. The safety of the procedure may be greatly reduced in such instances.