Novel Radiographic Measurement Algorithm Demonstrating a Link between Obesity and Lateral Skull Base Attenuation

Abstract

Objectives (1) To describe a validated algorithm for measuring tegmen thickness on computed tomography scans. (2) To compare the tegmen thickness in 3 groups: patients with spontaneous cerebrospinal fluid (CSF) leaks, obese controls, and nonobese controls. Study Design Retrospective review. Setting Patients with spontaneous CSF otorrhea often have highly attenuated tegmen plates. This is associated with obesity and/or idiopathic intracranial hypertension (IIH). No evidence exists, however, that objectively links obesity and/or IIH with skull base attenuation. Subjects and Methods This was a retrospective review from 2004 to the present. Patients with spontaneous CSF otorrhea and matched obese (body mass index [BMI] >30 kg/m2) and nonobese (BMI <30 kg/m2) controls were selected. Tegmen thickness was measured radiographically. Interrater validity was assessed. Results Ninety-eight patients were measured: 37 in the CSF group (BMI, 36.6 kg/m2), 30 in the obese group (BMI, 34.6 kg/m2), and 31 in the nonobese group (BMI, 24.2 kg/m2). The CSF group had a significantly thinner tegmen compared to both the obese control ( P < .01) and nonobese control ( P = .0004) groups. Obese controls had a thinner tegmen than nonobese controls ( P < .00001). A significant inverse correlation was detected between skull base thickness and BMI. Signs/symptoms of IIH were most commonly found in the CSF group. Good to very good strength of agreement was detected for measures between raters. Conclusion This is the first study to (1) quantify lateral skull base thickness and (2) significantly correlate obesity with lateral skull base attenuation. Patients who are obese with spontaneous CSF leaks have greater attenuation of their skull base than matched obese controls. This finding supports theories that an additional process, possibly congenital, has a pathoetiological role in skull base dehiscence.