Objective: To examine the relationship of body mass index (BMI) and the results of transmastoid repair of adult patients with spontaneous cerebrospinal fluid (CSF) otorrhea. Study Design: Retrospective Case Review. Setting: Tertiary Referral Private Practice. Patients: Patients presenting with spontaneous CSF otorrhea. Intervention:Transmastoid repair of temporal bone defect. Main Outcome Measures: Patients presenting with spontaneous CSF otorrhea over a consecutive 12-year period were examined. Clinic and operative records were reviewed to obtain the clinical presentation, examination findings, BMI, results of repair, location and size of skull base defect(s), and methods of repair. Preoperative MRIs were studied for evidence of empty sella and encephalocele. Results: Seventeen patients were included in the study. The mean age was 61 years and 9 patients were female. Average length of follow up was 21 months. Average body mass index (BMI) was 34.7 kg/m2. Evidence of partial or empty sella was present in 82% of MRIs reviewed. Sixty-five percent of patients had an encephalocele. Forty-seven percent had more than one bony defect along the tegmen tympani or mastoideum. All 17 patients were repaired initially using a transmastoid approach. The patient with the highest BMI (50.2 kg/m2) required revision surgery via a middle fossa approach 27 months after initial repair due to a recurrent leak.