The Loss of Temporal Muscle Volume is Associated with Poor Outcome in Patients with Subarachnoid Hemorrhage: An Observational Cohort Study

BACKGROUND: Intensive care unit (ICU) acquired weakness is a major contributor to poor functional outcome of ICU patients. Quantification of temporal muscle volume assessed on routine computed tomography (CT) scans may serve as a biomarker for muscle wasting in patients suffering from acute brain injury. METHODS: This is a retrospective analysis of prospectively collected data. Temporal muscle volume was assessed on head CT scans of consecutive patients with spontaneous subarachnoid hemorrhage within prespecified time frames (on admission, then weekly ± 2 days). Whenever possible, temporal muscle volume was assessed bilaterally and averaged for the analysis. Poor functional outcome was defined as a 3-month modified Rankin Scale Score ≥ 3. Statistical analysis was performed using generalized estimating equations to handle repeated measurements within individuals. RESULTS: The analysis comprised 110 patients with a median Hunt & Hess score of 4 (interquartile range 3–5). Median age was 61 (50–70) years, 73 patients (66%) were women. Baseline temporal muscle volume was 18.5 ± 0.78 cm(3) and significantly decreased over time (p < 0.001) by a mean of 7.9% per week. Higher disease severity (p = 0.002), hydrocephalus (p = 0.020), pneumonia (p = 0.032), and bloodstream infection (p = 0.015) were associated with more pronounced muscle volume loss. Patients with poor functional outcome had smaller muscle volumes 2 and 3 weeks after subarachnoid hemorrhage compared with those with good outcome (p = 0.025). The maximum muscle volume loss during ICU stay was greater in patients with poor functional outcome (− 32.2% ± 2.5% vs. − 22.7% ± 2.5%, p = 0.008). The hazard ratio for poor functional outcome was 1.027 (95% confidence interval 1.003–1.051) per percent of maximum muscle volume loss. CONCLUSIONS: Temporal muscle volume, which is easily assessable on routine head CT scans, progressively decreases during the ICU stay after spontaneous subarachnoid hemorrhage. Because of its association with disease severity and functional outcome, it may serve as a biomarker for muscle wasting and outcome prognostication.