Preoperative headband assessment for semi-implantable bone conduction hearing devices in conductive hearing loss: Is it useful or misleading?

OBJECTIVE: To establish whether preoperative assessment using a conventional, percutaneous bone conducting implant (pBCI) processor on a headband accurately represents postoperative performance of a semi-implantable BCI (siBCI). STUDY DESIGN: Retrospective case series. SETTING: Tertiary otology unit. PATIENTS: Five patients with chronic otitis media (implanted unilaterally) and one with bilateral congenital ossicular fixation (implanted bilaterally). INTERVENTION(S): Semi-implantable bone conduction hearing implant. MAIN OUTCOME MEASURE(S): Functional hearing gain; preoperative (headband) versus postoperative (aided) speech discrimination; unaided bone conduction (BC) versus postoperative (aided) soundfield threshold. RESULTS: Significant functional gain was seen at all frequencies (one-tailed t test p < 0.01; n = 7). There was a 50 dB improvement in median speech reception threshold (SRT) from 70 dB unaided to 20 dB aided. Compared to the preoperative BC, aided siBCI thresholds were worse at 0.5 kHz, but at frequencies from 1 to 6 kHz, the siBCI closely matched the bone curve (p < 0.01). The siBCI performed better than both pBCI processors on a headband at 3 to 4 kHz, except 1 kHz (p < 0.01). CONCLUSIONS: BC thresholds may be a better indicator of implant performance than headband assessment. Candidacy assessment for siBCI implantation that relies on headband testing with pBCI processors should be interpreted with caution because the headband may under-represent the implanted device. This seems to be especially true at 3 kHz and above and may make it difficult for surgeons to conduct accurate informed consent discussions with patients about the realistic anticipated outcomes and benefits of the procedure.