Perimesencephalic Nonaneurysmal Subarachnoid Hemorrhage After Clipping of an Unruptured Aneurysm

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH) is a benign form of subarachnoid hemorrhage with an excellent clinical outcome. The cause of PNSAH remains unknown. We report a case of PNSAH in a patient with a history of clipping of an unruptured aneurysm. PNSAH after clipping of an unruptured aneurysm is extremely rare. A 56-year-old man with a history of clipping surgery for an unruptured aneurysm 10 months previously presented with severe headache. No precipitating causes were shown; however, the patient had been engaged in an exertional activity before the event. After conservative treatment, he was discharged home without any complication from the hemorrhage. On the basis of this case report, clinicians should consider the possibility of PNSAH in a patient who had an unruptured aneurysm previously treated with clipping. Nevertheless, diagnostic workup can be more important than keeping in mind that a subarachnoid hemorrhage might be a PNSAH.