Posterior Fossa Chronic Subdural Hematoma Associated with Supratentorial Chronic Subdural Hematoma

OBJECTIVE: Chronic subdural hematoma (CSDH) in the posterior fossa has until now been reported in only 16 patients. This study clarified the frequency and characteristics of the posterior fossa CSDH through the use of magnetic resonance imaging (MRI) in patients with supratentorial CSDH. METHODS: We retrospectively examined presurgical MRI findings in patients with supratentorial CSDH who underwent surgery between 2006 and 2020. RESULTS: MRI revealed posterior fossa CSDH in 24 (7.3%) of 329 patients. Multivariable analyses demonstrated that anticoagulant treatment (P = 0.033, odds ratio [OR] 3.53), cerebrospinal fluid leak (P = 0.001, OR 18.5), and lack of previous trauma 3 weeks or more before admission (P = 0.027, OR 3.03) were risk factors of posterior fossa CSDH. Computed tomography could not show the hematomas in 20 patients (83.3%). All the posterior fossa CSDHs improved after supratentorial CSDH drainage. CONCLUSIONS: Posterior fossa CSDH was observed on MRI in a minority of patients with supratentorial CSDH. Although most patients with posterior fossa CSDH had good outcomes, large posterior fossa CSDH sometimes must be treated surgically, according to previous reports.