Recurrent idiopathic perimesencephalic subarachnoid hemorrhage

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH) is a benign variant of SAH defined by clinical symptoms of SAH, a characteristic pattern of extravasated blood on noncontrast CT, and negative findings on cerebral angiography. This syndrome carries a favorable prognosis with reportedly no risk of recurrent hemorrhage. The authors present the case of a 62-year-old man with no significant medical history who experienced recurrent, spontaneous episodes of PNSAH within the course of 5 months. No precipitating causes were identified, but the patient had been involved in exertional activities preceding both events. To the authors' knowledge, this is the first conclusive report of recurrent, idiopathic PNSAH. The findings suggest that while the risk of recurrent hemorrhage in the setting of PNSAH is far less than that for aneurysmal SAH, rebleeding can still occur. The authors speculate on the etiology of this rare phenomenon. (DOI: 10.3171/2011.5.JNS102020)