Abstract
Objective The main purpose of this article is to investigate the prevalence and features of
posterior fossa defects (PFD) in spontaneous cerebrospinal fluid leaks (sCSFL).
Design This is a retrospective case series.
Setting Tertiary skull base center.
Participants Consecutive adults undergoing lateral skull base repair of sCSFL between 2003 and
2018.
Main Outcome Measures 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.
Results 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, p = 0.005) and symptomatic bilateral leaks (OR: 9.67, 95% CI: 2.22–40.17, p = 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.
Conclusion 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.
Keywords
lateral skull base encephaloceles - spontaneous cerebrospinal leak - posterior fossa
- defects - combined transmastoid–middle cranial fossa approach - arachnoid granulation
