Systematic errors in bone conduction audiometry

Evidence of progression and fluctuation of hearing impairment in branchio-oto-renal syndrome

We retrospectively analysed long-term serial audiometry data from patients with branchio-oto-renal (BOR) syndrome to show the features of progression and fluctuation in hearing impairment and relate the findings to age and magnetic resonance imaging (MRI) findings in the petrosal bones. Thirty-two clinically affected BOR patients from six Dutch families (A-F) were included. Audiograms were available in 24 cases, covering followup intervals of between 3 and 30 years, and suitable for individual statistical analysis in 16 cases: 14 cases also had MRI findings. Significant progression in hearing impairment was found in 10 cases, while findings of significant fluctuation were made in seven cases. These findings did not clearly correlate with MRI findings. Substantial fluctuation occurred only in cases followed at a relatively young age. Patients with an enlarged endolymphatic duct and/or sac showed significantly higher sensorineural hearing thresholds than those with either normal MRI findings or cochlear/labyrinthine hypoplasia with or without enlarged duct or sac. We conclude that progressive, fluctuant hearing loss occurred in some BOR patients; however, only young patients showed substantial threshold fluctuation. BOR patients with an enlarged endolymphatic duct and/or sac on MRI seemed to be predisposed to developing more severe hearing impairment.

Bone conduction reception: head sensitivity mapping

This study sought to identify skull locations that are highly sensitive to bone conduction (BC) auditory signal reception and could be used in the design of military radio communication headsets. In Experiment 1, pure tone signals were transmitted via BC to 11 skull locations of 14 volunteers seated in a quiet environment. In Experiment 2, the same signals were transmitted via BC to nine skull locations of 12 volunteers seated in an environment with 60 decibels of white background noise. Hearing threshold levels for each signal per location were measured. In the quiet condition, the condyle had the lowest mean threshold for all signals followed by the jaw angle, mastoid and vertex. In the white noise condition, the condyle also had the lowest mean threshold followed by the mastoid, vertex and temple. Overall results of both experiments were very similar and implicated the condyle as the most effective location.

Bone conduction variation poststapedotomy

We evaluated the variation in bone conduction auditory thresholds in patients undergoing surgical intervention for otosclerosis as part of our report on the use of surgery in patients with a small air-bone gap. Of the 110 patients who underwent stapedotomy, 45 were treated by traditional surgery and 65 with carbon dioxide laser, with a follow-up of 3 years at 500-, 1000-, 2000-, and 3000-Hz frequencies. Both surgical techniques resulted in improvements in air conduction in more than 95% of cases; bone conduction improved more in patients treated with carbon dioxide laser (7.1 dB) compared to those treated with traditional surgery (4 dB) (P < .01). Furthermore, improvement in bone conduction was greater and more frequent in younger subjects (below 45 years) (P < .05). In conclusion, this study allows us to express a positive prognosis when considering otosclerotic patients with sensorineural hearing loss and small air-bone gap.