Papers of the Week

Perimesencephalic non-aneurysmal subarachnoid hemorrhage (PNSH) is characterized by a typical pattern of localized pretruncal hemorrhage on head computed tomography (CT). PNSH is usually associated with a benign clinical course and a lower incidence of complications. The etiology is unknown but has many proposed explanations, including venous injury or rupture followed by thrombosis of a ruptured microaneurysm.