Ruptured aneurysm at the cortical segment of the posterior inferior cerebellar artery

We report a rare case of a ruptured aneurysm at the cortical segment of the posterior inferior cerebellar artery (PICA) with a branching complex that was feeding the bilateral cerebellar hemispheres. A 70-year-old woman suddenly sustained a severe headache and vomiting. CT scan revealed diffuse subarachnoid haemorrhage with fourth and lateral ventricular haemorrhage, which suggested typical aneurysmal bleeding in the posterior circulation. No aneurysm was detected on the initial angiogram. This angiogram also showed no significant evidence of other lesions that could be the origin of the bleeding. A third angiogram was performed 15 days from the ictus and revealed a distal PICA saccular aneurysm. The aneurysm was located at the cortical segment, and the artery was branching to both of the cerebellar hemispheres. This could be more clearly visualised during the ensuing operation, and neck clipping was performed. The patient recovered without neurological deterioration. Subarachnoid haemorrhage with blood in the fourth ventricle may indicate a ruptured aneurysm on the distal segment of the PICA with a branching variation, feeding the contra-lateral hemisphere, which is rarely located in this position.