A Case of Quadrigeminal Variant of Perimesencephalic Nonaneurysmal Subarachnoid Hemorrhage

Abstract The incidence of perimesencephalic subarachnoid hemorrhage (PMSAH) is rare, 0.5 in 100,000 adults. It comprises 5 to 10% of all SAHs and approximately 33% of all nonaneurysmal SAH. Quadrigeminal SAH is a variant of perimesencephalic nonaneurysmal subarachnoid hemorrhage (PMNASAH) that is not well described in the literature. It may comprise up to one-fifth of PMNASAH cases and carries a similar benign prognosis. This variant of PMSAH is characterized by blood centered in the quadrigeminal cistern and limited to the superior vermian and posterior perimesencephalic cisterns. Noncontrast computed tomography of the brain is the initial investigation of choice, while four-vessel cerebral angiogram is the gold standard for the diagnosis of SAH. We report a case at our institute.