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/m2. 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.