Delayed cerebral ischemia manifesting as peduncular hallucinosis after aneurysmal subarachnoid hemorrhage--three case reports.

Three cases of peduncular hallucinosis occurred in patients with aneurysmal subarachnoid hemorrhage. All patients underwent early clipping of the ruptured aneurysms of the anterior circulation. Several days after onset of subarachnoid hemorrhage, the patients complained of vivid visual hallucinations associated with abnormal sleep-waking rhythms, suggesting a diagnosis of peduncular hallucinosis. The hallucinations disappeared with administration of an increased dose of dobutamine. These findings indicated that peduncular hallucinosis might be a manifestation of delayed cerebral ischemia after subarachnoid hemorrhage. No other possible cause of neurological deficits such as hydrocephalus, cerebral infarcts, or metabolic encephalopathies was identified. Damage to the ascending reticular activating system has been implicated in the pathogenesis of peduncular hallucinosis. Cerebral vasospasm in the perforating arteries of the ascending reticular activating system was probably the cause of the hallucinosis in our patients.