Quadrigeminal variant of perimesencephalic nonaneurysmal subarachnoid hemorrhage

OBJECTIVE: Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSH) is a benign entity with a low risk of rebleeding. The most widely accepted definition emphasizes the presence of blood ventral to the midbrain or pons on early computed tomography. We sought to determine the frequency of PNSH with blood centered in the quadrigeminal cistern. METHODS: We reviewed a prospectively collected database of all patients admitted to our institution over a 2.5-year period with subarachnoid hemorrhage (SAH) and identified PNSH patients from early computed tomographic scans and negative four-vessel angiograms. RESULTS: Of 220 SAH patients, we identified 9 with PNSH. Two (22%) of these patients had SAH centered in the quadrigeminal cistern without pretruncal blood, negative repeat angiograms, and an uncomplicated clinical course. CONCLUSION: Quadrigeminal SAH is a variant of PNSH that is not well described in the literature. It may comprise up to one-fifth of PNSH cases and carries a similar benign prognosis.