Quadrigeminal non-aneurysmal subarachnoid hemorrhage--a true variant of perimesencephalic subarachnoid hemorrhage. Case report.

Spontaneous non-aneurysmal subarachnoid hemorrhage (SAH) centered in the quadrigeminal cistern has been proposed as a variant of perimesencephalic non-aneurysmal SAH (PNSH). Some authors contest the existence of this entity, claiming it results either from head trauma or an undiscovered P2-P3 aneurysm, and conclude that all PNSH arise in front of the brainstem in a 'pretruncal' location. We report a patient with a quadrigeminal pattern of subarachnoid blood who was investigated with two digital catheter angiograms, including 3-D angiography, plus a high-resolution computed tomography angiogram. No abnormal findings were present and the patient had an excellent outcome. We propose that the more common pretruncal PNSH and less common quadrigeminal PNSH are two types of perimesencephalic SAH with separate, distinct etiologies, both of which have a more benign clinical course than aneurysmal SAH.