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

Abstract

Objectives: (1) Describe a validated measurement instrument to quantify tegmen thickness on computed tomography (CT) images. (2) Compare tegmen thickness in 3 groups: patients with spontaneous cerebrospinal fluid (CSF) leaks, obese controls, and nonobese controls. Methods: Retrospective review from 2005 to present. Patients with a diagnosis of spontaneous CSF otorrhea and dedicated temporal bone CT scans were included. Matched obese (body mass index [BMI] >30) and nonobese (BMI <30) controls were selected from a pool of cochlear implant candidates. The tegmen was measured radiographically in all patients at pre-defined points. Independent, blinded measurements were made by 3 of the authors and compared for interrater validity. Results: Ninety-nine patients were measured: 39 in the CSF group (BMI 35.9), 29 in the obese group (BMI 34.6), and 31 in the nonobese group (BMI 24.2). The CSF group had a significantly thinner aggregate tegmen thickness (0.82 mm ± 0.19) compared with both obese controls (0.99 mm ± 0.18, P = .007) and nonobese controls (1.26 mm ± 0.2, P < .001). Obese controls were thinner than non obese controls ( P < .001). Signs/symptoms of benign intracranial hypertension (BIH) were most commonly found in the CSF group. No other factors significantly affected thickness. Good to excellent correlation of measurements was found between all 3 raters. Conclusions: This is the first study to (1) quantify lateral skull base thickness and (2) significantly correlate obesity with lateral skull base attenuation. Obese spontaneous CSF leak patients may have even greater attenuation of their skull base than matched obese controls. This finding may further support theories that an additional process, such as BIH, may play an important pathophysiologic role in skull base thinning.