A single-center retrospective study on clinical features and outcomes of perimesencephalic non-aneurysmal subarachnoid hemorrhage patients.

Perimesencephalic non-aneurysmal subarachnoid hemorrhage (pmSAH) is a subtype of subarachnoid hemorrhage (SAH) where the bleeding source remains unclear. It is generally associated with a benign clinical course compared to other SAH types. This study retrospectively analyzed 198 pmSAH patients admitted between January 2019 and December 2023, along with 137 non-perimesencephalic non-aneurysmal subarachnoid hemorrhage (npmSAH) and 198 aneurysmal SAH patients as controls. Results showed that pmSAH incidence accounted for approximately 5.6% of all SAH cases and 59.1% of non-aneurysmal SAH cases. pmSAH patients exhibited milder clinical severity, with higher Glasgow Coma Scale scores and lower Hunt-Hess grades compared to aSAH and npmSAH patients. At onset, pmSAH patients were less likely to experience loss of consciousness, incontinence, or convulsions. They also had fewer complications, shorter hospital stays, and a lower proportion of poor prognosis. Multivariate logistic regression identified complications and Hunt-Hess grade as independent risk factors for poor prognosis in pmSAH. In conclusion, pmSAH patients demonstrated relatively mild clinical courses, fewer complications, and better prognosis. However, occasional occurrences require further attention.