IntroductionAneurysmal subarachnoid haemorrhage (aSAH) is a condition with significant morbidity and mortality. In the context of acute brain injury, frailty, sarcopaenia and osteopaenia have become increasing concerns. Multiple indices have been devised in various surgical specialties to predict outcome and guide management. In this study, we examined whether such markers have relevance towards outcomes from acute brain conditions, such as aSAH. MethodsAn observational study in a tertiary neurosurgical unit on 51 consecutive patients with ruptured aSAH was performed. We compared various frailty indices (modified frailty index 11, and 5, and the National Surgical Quality Improvement Program score [NSQIP]), temporalis (TMT) and zygoma thickness (markers of sarcopaenia and osteopaenia), against traditional markers (age, World Federation of Neurological Surgery and modified Fisher scale [MFS]) for aSAH outcomes. ResultsTMT was the best performing marker in our cohort with an AUC of 0.82, Somers’ D statistic of 0.63 and Tau statistic 0.25. Of the frailty scores, the NSQIP performed the best (AUC 0.69, Somer’s D 0.40, Tau 0.16), at levels comparable to traditional markers of aSAH, such as MFS (AUC 0.68, Somer’s D 0.43, Tau 0.17). After multivariate analysis, patients with TMT ≥5.5mm (defined as non-frail), were less likely to experience complications (OR 0.20 [0.06 – 0.069], p = 0.011), and had a larger proportion of favourable mRS on discharge (95.0% vs. 58.1%, p = 0.024) and at 3-months (95.0% vs. 64.5%, p = 0.048). However, the gap between unfavourable and favourable mRS was insignificant at the comparison of 1-year outcomes. ConclusionTMT, as a marker of sarcopaenia, correlated well with the presenting status, and outcomes of aSAH. Frailty, as defined by NSQIP, performed at levels equivalent to aSAH scores of clinical relevance, suggesting that, in patients presenting with acute brain injury, both non-neurological and neurological factors were complementary in the determination of eventual clinical outcomes. Further validation of these markers, in addition to exploration of other relevant frailty indices, may help to better prognosticate aSAH outcomes and allow for a precision medicine approach to decision making and optimization of best outcomes Trial registrationNot applicable