Cerebrospinal Fluid Leaks of the Posterior Fossa: Patient Characteristics and Imaging Features.

The main purpose of this article is to investigate the prevalence and features of posterior fossa defects (PFD) in spontaneous cerebrospinal fluid leaks (sCSFL).  This is a retrospective case series.  Tertiary skull base center.  Consecutive adults undergoing lateral skull base repair of sCSFL between 2003 and 2018.  The following data were collected: demographics, comorbidities, radiology and intraoperative findings, and surgical outcomes including complications and need for revision surgery or shunt placement. Patients with incomplete data or leaks following skull base surgery, trauma, or chronic ear disease were excluded.  Seventy-one patients (74% female, mean age 56.39 ± 11.50 years) underwent repair of spontaneous lateral skull base leaks. Eight ears (7 patients, 11.1%) had leaks involving the posterior fossa plate in addition to defects of the tegmen mastoideum (50%), tegmen tympani (25%), or both (25%). Patients with PFDs more often had bilateral tegmen thinning on imaging (75%, odds ratio [OR]: 10.71, 95% confidence interval [CI]: 2.20-54.35, 0.005) and symptomatic bilateral leaks (OR: 9.67, 95% CI: 2.22-40.17,  = 0.01. All PFD patients had arachnoid granulations adjacent to ipsilateral mastoid cell opacification. However, this finding was often subtle and rarely included on the radiology report. There was no significant difference in body mass index, age, presenting complaints, or operative success between the PFD and isolated tegmen defect sCSFL cohorts.  The posterior fossa is an uncommon location for sCSFL. Careful review of preoperative imaging is often suggestive and can inform surgical approach. PFD patients are similar to those with isolated tegmen-based defects in presentation, comorbidities, and outcomes.