Nonaneurysmal Perimesencephalic Subarachnoid Hemorrhage as an Atypical Initial Presentation of Cerebral Venous Sinus Thrombosis: A Case Report.

BACKGROUND Subarachnoid hemorrhage is rarely the first presentation of cerebral venous sinus thrombosis. This case study emphasizes the presentation of perimesencephalic subarachnoid hemorrhage due to cerebral venous sinus thrombosis and the importance of neurovascular imaging for reliable diagnosis of nonaneurysmal perimesencephalic subarachnoid hemorrhage due to cerebral venous sinus thrombosis. CASE REPORT We describe a case of cerebral venous sinus thrombosis manifesting initially as subarachnoid hemorrhage. Non-contrast computed tomography showed evidence of subarachnoid hemorrhage involving the prepontine and suprasellar cisterns. Cerebral convexities were totally spared while parenchymal microbleeding was observed in the midbrain. The diagnosis was confirmed by magnetic resonance arteriography and venography. Treatment included low molecular weight heparin and warfarin therapy to restore the international normalization ratio of the patient to 2.5, followed by oral warfarin therapy for 3 months. CONCLUSIONS Cerebral venous sinus thrombosis manifesting initially as subarachnoid hemorrhage is rare. Subarachnoid hemorrhage caused by cerebral venous sinus thrombosis has been reported previously to be confined to the cerebral convexities, sparing the basal cistern. However, this is not always the case where the radiological confirmation suggests the occurrence of nonaneurysmal perimesencephalic subarachnoid hemorrhage.