Presentation
Sudden onset of headache. No loss of consciousness or neurological deficit.
Patient Data
Age: 45 years
Gender: Male
Axial non-contrast

Blood is seen in the perimesencephalic cistern.
Case Discussion
This is the typical distribution of perimesencephalic subarachnoid hemorrhage, which usually is non-aneurysmal in origin.
This patient went on to have a CTA which demonstrated no evidence of an aneurysm. They were further evaluated with DSA and followup and he has remained well.