Acute subdural hematoma (aSDH) is among the most common injury types encountered by neurosurgeons, and carries a poor prognosis, particularly in the elderly. As the incidence of aSDH in the elderly population rises, identifying those patients who may benefit from operative intervention is crucial. This systematic review aimed to identify data on prognostic factors or indices, such as the modified frailty index, that may help predict outcome, and hence guide management. A comprehensive search of online databases was conducted by two independent authors, and data on prognostic factors and outcomes were extracted. The quality of the evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. Of 769 studies identified in the initial search, 7 satisfied inclusion and exclusion criteria. Mortality and morbidity varied considerably among studies. Initial Glasgow Coma Scale (GCS) of 3-8 was the most consistently reported negative prognostic feature. Several studies evaluated the impact of medical comorbidities and premorbid frailty, but were limited by small sample size. A previous history of pneumonia was shown to increase the risk of Glasgow Outcome Score (GOS) 1-3 (odds ratio [OR] 6.4 [95% CI 1.6-25.2], p = 0.04) in a single study, which also reported a greater increase in GOS at 3 months in those with fewer than five comorbidities (56% vs. 19%, p < 0.01). There are limited data describing prognostic factors or the use of frailty indices within the specific group of elderly patients with aSDH. Prospective research is needed to evaluate the utility of accurate and validated assessments of frailty to enhance the neurosurgeon's ability to appropriately manage this complex and expanding patient group.

Heterogeneity and the presence of bias limit our confidence in these findings. However, the variance in the interpretation of CTB between emergency clinicians and radiologists suggests that interventions towards improving accuracy may be useful.

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