Incremental Prognostic Value of CT Indices Derived from Midline Shift and Hematoma Thickness in Acute Subdural Hematoma

Background: In acute subdural hematoma (ASDH), early risk stratification relies heavily on hematoma thickness (HT) and midline shift (MLS). Composite indices derived from these measures have been proposed to better characterize mass effect, but their incremental prognostic value beyond core clinical predictors remains uncertain. Methods: A prospective two-center cohort study of adults with ASDH was conducted. The primary outcome was 6-month unfavorable functional status (Glasgow Outcome Scale 1–3). Prespecified multivariable logistic regression models included a base model comprising age and admission Glasgow Coma Scale (GCS) and extended models incorporating either the MLS-to-HT ratio or the Zumkeller Index. Model performance was assessed using discrimination, calibration, decision curve analysis, and internal validation. Results: Among 152 patients, 112 (73.7%) had an unfavorable outcome. Both the MLS-to-HT ratio (adjusted OR 1.34 per 0.1-unit increase, 95% CI 1.09–1.65) and the Zumkeller Index (adjusted OR 1.13 per mm increase, 95% CI 1.01–1.28) were independently associated with outcome. The base model achieved an AUC of 0.78; addition of the MLS-to-HT ratio and Zumkeller Index yielded AUCs of 0.79 and 0.78, respectively, without materially improving overall model performance or clinical utility. Conclusion: In ASDH, CT-derived composite indices provide little incremental prognostic value beyond age and admission GCS and are unlikely to meaningfully improve clinical risk stratification. Preprint notice: This manuscript is a preprint and has not undergone peer review. The manuscript is currently under editorial consideration at Trauma Surgery & Acute Care Open.