Posterior Fossa Spontaneous Cerebrospinal Fluid Leaks

Objective: Describe the diagnosis and management of spontaneous lateral skull base cerebrospinal fluid (CSF) leaks that originate from the posterior fossa. Study Design: Retrospective case review. Setting: Tertiary university hospital. Patients: Adult patients from 2005 to 2015 who underwent surgical repair of a spontaneous lateral skull base CSF leak with intraoperative confirmation of a posterior fossa leak source. Intervention: Surgical repair. Main Outcome Measures: CSF leak resolution. Results: Five patients had CSF leaks from the posterior fossa. The mean age at presentation was 54 years old (range, 19-79), the mean body mass index (BMI) was 32.6 (standard deviation [SD], 8.4), and the mean follow-up length was 34.6 months (SD, 19.4). Presentations did not differ from CSF leaks through middle fossa defects, including three patients with a history of meningitis and all patients with clear otorrhea following tympanostomy tube placement. All patients had resolution of the leak after surgical repair, but two patients required revision surgery for persistent leaks and one patient had a postoperative infection. Surgical approaches included one middle fossa, two transmastoid, one combined middle fossa/transmastoid, and one transcanal. Radiographic studies suggested a posterior fossa source in all cases but findings were often subtle. Conclusion: Posterior fossa CSF leaks represent a rare subset of spontaneous lateral skull base leaks. Diligent radiographic review and intraoperative assessment of the posterior fossa plate are crucial. The size and location of the defect dictates the optimal surgical approach. Surgeons should consider a posterior fossa source in failed repairs or when the initial surgery did not fully evaluate the posterior fossa plate.