Clinical severity of aneurysmal subarachnoid hemorrhage over time: systematic review

The incidence of aneurysmal subarachnoid hemorrhage (aSAH) is well studied. Yet, little is known about the trend of aSAH severity. This systematic review aims to analyze the distribution of aSAH severity over time. We performed a systematic review of the literature according to the PRISMA-P guidelines. We included studies from January 1968 up to December 2022. Studies were included if they either reported the severity of aSAH as single increments of the corresponding 5-point scale or as a binary measure (good grade 1-3, poor grade 4-5) on the Hunt and Hess (HH) or World Federation of Neurosurgical Societies (WFNS) scale. Studies with fewer than 50 patients, (systematic) reviews, and studies including non-aSAH patients were excluded. A total of 2465 publications were identified, of which 214 met the inclusion and exclusion criteria. In total, 102,845 patients with an aSAH were included. Over the last five decades the number of good-grade HH (0.741 fold, p = 0.004) and WFNS (0.749 fold, p < 0.001) has decreased. Vice versa, an increase in number of poor grade HH (2.427 fold, p = 0.004), WFNS (2.289 fold, p < 0.001), as well as HH grade 5 (6.737 fold, p = 0.010), WFNS grade 4 (1.235 fold, p = 0.008) and WFNS grade 5 (8.322 fold, p = 0.031) was observed. This systematic review shows a worldwide 2-3 fold increase of poor grade aSAH patients and an 6-8 fold increase of grade 5 patients, over the last 50 years. Whether this evolution is due to more severe hemorrhage, improvements in neuro-intensive care and prehospital management, or to a change in grading behavior is unknown. This study strongly emphasizes the necessity for an improved grading system to differentiate grade 4 and grade 5 patients for meaningful clinical decision- making.