Takeaway
For subarachnoid hemorrhage (SAH), the clinical course of SAH that is angiographically negative with aneurysmal pattern (aanSAH) is intermediate between aneurysmal (aSAH) and perimesencephalic SAH (panSAH), with better prognosis for aanSAH versus aSAH.
Why this matters
Improved recognition and understanding of the clinical course of aanSAH relative to panSAH, which has a good prognosis, and aSAH, which has a poor prognosis, will help clinicians advise and treat patients with SAH.