Cochlear promontory anatomy relevant to development of subendosteal and transpromontory electrodes using 192‐section ultra‐high resolution temporal bone CT imaging

OBJECTIVE: To characterize normative adult ranges for cochlear promontory thickness relevant to the development of subendosteal and transpromontory electrodes to rehabilitate various neurotologic disorders. PATIENTS: Adults (≥18 years). INTERVENTION: In vivo radiologic assessment using a 192‐slice CT scanner (Force‐192; Siemens Healthcare) with ultrahigh‐resolution scan mode combined and iterative reconstruction. MAIN OUTCOME MEASURE: Cochlear promontory thickness. RESULTS: Among 48 included patients (96 ears), the mean (SD) age was 56 (18) years (range 25–94) and included 25 (52%) women. Of that 12 patients (25%) had osteopenia (n = 6) or osteoporosis (n = 6). The mean (SD) body mass index was 28 (5) kg/m(2). The mean (SD) promontory thickness for the 96 temporal bones under study was 1.22 (0.24) mm (range 0.55–1.85). There was not a statistically significant association between age and promontory thickness (correlation coefficient .08; p = .44). Promontory thickness was significantly greater for men than women (mean 1.28 vs. 1.17 mm; p = .03) and increased with increasing body mass index (correlation coefficient .30; p = .004). Last, promontory thickness was significantly less for patients with osteopenia or osteoporosis compared with those without these conditions (mean 1.09 vs. 1.27 mm; p = .002). CONCLUSIONS: Cochlear promontory thickness can vary by almost 1.5 mm across patients and is significantly associated with patient sex, body mass index, and comorbid osteopenia/osteoporosis. Subendosteal and transpromontory electrode placement techniques must account for this degree of variability. LEVEL OF EVIDENCE: IV