Traumatic Posterior Fossa Subdural Hemorrhage: A Multicenter, Retrospective Cohort Study.
Traumatic posterior fossa subdural hemorrhage (SDH) is a rare subtype of subdural hemorrhage in head injuries. Existing data on its pathophysiology and outcome are currently limited; therefore, the condition is not yet fully understood. The present study aimed to determine the incidence, outcome, and prognostic factors for traumatic posterior fossa SDH. We performed a retrospective cohort study using the nationwide trauma registry Japan Trauma Data Bank. We identified adult patients (i.e., aged ≥18 years) who had posterior fossa SDH after blunt head trauma from 2004 to 2015. The primary endpoint was in-hospital mortality. We compared patients with and without posterior fossa SDH and adjusted for confounders using a multivariate logistic regression model. A total of 75,838 patients had blunt head injuries. Of these, 266 (0.35%) had posterior fossa SDH, and 177 (median age, 69 years; interquartile range, 55-76) were eligible for analysis. The distribution of the Glasgow Coma Scale (GCS) score was bimodal, and the median score was 14 (interquartile range, 9-15). The mortality rate was 16.9% (95% confidence interval [CI], 11.7%-23.3%). A large posterior fossa SDH (>30 cm3; >1 cm thick), low GCS score on arrival, and the presence of a skull fracture were significantly associated with mortality, with an adjusted odds ratio of 4.51 (95% CI, 1.46-13.9), 0.82 (95% CI, 0.73-0.92), and 4.59 (95% CI, 1.52-13.9), respectively. Traumatic posterior fossa SDH was extremely rare in our data set. Mortality correlated with the size of the SDH, GCS score on admission, and the presence of a skull fracture.