Reduced Masseter Muscle Area Predicts the 6-Month Outcome After Mild Traumatic Brain Injury in Older Adults.

Mild traumatic brain injury (mTBI) in older patients is a common condition in neurosurgery, often linked to poor long-term outcomes, especially when accompanied by frailty. Sarcopenia contributes to this frailty and can be assessed through transverse imaging methods. This study aimed to assess the prognostic value of the masseter muscle cross-sectional area (MCSA) as determined from admission CT head scans in older patients with mTBI. This retrospective study identified older patients with mTBI who were admitted to our hospital from April 2013 to December 2022. The Glasgow Outcome Scale Extended (GOSE) was utilized to assess neurological outcomes at 6 months follow-up, which were divided into complete recovery (GOSE = 8) and incomplete recovery (GOSE ≤ 7). We measured the average MCSA using admission CT scans and evaluated the consistency of these measurements. Multivariable logistic regression was conducted to evaluate the association between reduced MCSA and 6-month clinical outcomes in older mTBI patients while adjusting for age, gender, and comorbidity. The study involved 227 patients, 135 (59.5%) males and 92 (40.5%) females, with a mean age of 74.1 years. 92 (40.5%) had an adverse clinical outcome by the end of follow-up. The intra- and inter-observer reliability of the MCSA measurements was good to excellent (ICCs = 0.955-0.972 and 0.856-0.892). MCSA decreased with age (Pearson's r = -0.290, p < 0.001). Males had higher MCSA than females (p < 0.001). The optimal MCSA cutoff values for predicting 6-month clinical outcomes were 358.75 mm2 for male and 263.25 mm2 for female patients. Reduced MCSA was associated with 6-month clinical outcomes in univariate and multivariate logistic analyses (OR = 0.131, 95% CI: 0.063-0.273; p < 0.001). The MCSA was linearly associated with incomplete recovery (p < 0.001, P for nonlinear = 0.127). MCSA measurements from initial scans were reliable, providing prognostic information that supplemented existing predictors of poor outcomes in older mTBI patients.