Calvarium thinning in patients with spontaneous cerebrospinal fluid leak.

OBJECTIVE: To determine the thickness of the calvarium in patients with spontaneous cerebrospinal fluid (CSF) leaks. STUDY DESIGN: Case control study. SETTING: University of Iowa Hospitals and Clinics. PATIENTS: Those with a confirmed spontaneous CSF leak compared to non-obese (body mass index, BMI < 30) and obese (BMI ≥ 30) cochlear implant (CI) control groups. All patients had to have temporal bone CT scans that fit specified criteria. INTERVENTION: Bilateral volumetric analysis of the squamous temporal bone and the zygoma in all patients. Assessment of patient age, sex, BMI, and medical comorbidities. MAIN OUTCOME MEASURE: Assessment of the average thickness of the squamous temporal bone and zygoma compared to control groups. RESULTS: The average BMI of patients with spontaneous CSF leaks was significantly higher than non-obese CI controls (43.73 ± 9.19 vs. 24.60 ± 3.10; P < 0.0001). The calvarium in patients with spontaneous CSF leaks was 23% thinner than both non-obese CI controls (3.29 ± 0.68 vs. 4.25 ± 0.58; P < 0.0001) and obese CI controls (3.29 ± 0.68 vs. 4.27 ± 0.68; P < 0.0001). In addition, the skull thickness of obese CI patients (body mass index, BMI = 37.34 ± 6.1) was not significantly different from non-obese CI controls (4.27 ± 0.68 vs. 4.25 ± 0.58; P = 0.92). The extracranial zygoma was not significantly different among the three groups (ANOVA = 0.9). In our study groups, 5.8% of both CI control groups had the diagnosis of obstructive sleep apnea (OSA), whereas 46.2% of the spontaneous CSF leak patients presented with the diagnosis of OSA. CONCLUSION: Patients with spontaneous CSF leak are more likely to be obese, have the diagnosis of OSA, and show thinning of their entire calvarium that is independent of BMI. These data suggest an additional obesity-associated intracranial process contributes to skull thinning.