Hyperacute perimesencephalic subarachnoid hemorrhage: Demonstration of blood extravasation with MRI

Perimesencephalic subarachnoid hemorrhage (SAH) is a benign subtype of SAH without known vascular pathology. We report a case of current subarachnoid bleeding in the vicinity of the basilar artery. The patient was on anticoag ulation medication and had sustained a head injury 2 days earlier. The blee ding was documented by contrast agent extravasation in MRI. Because of the isointensity of hyper acute blood to CSF in conventional T2 sequences, FLAI R images are mandatory for diagnosis in the hyperacute state.