Amplification in the rehabilitation of unilateral deafness: speech in noise and directional hearing effects with bone-anchored hearing and contralateral routing of signal amplification.

OBJECTIVE: Vibromechanical stimulation with a semi-implantable bone conductor (Entific BAHA device) overcomes some of the head-shadow effects in unilateral deafness. What specific rehabilitative benefits are observed when the functional ear exhibits normal hearing versus moderate sensorineural hearing loss (SNHL)? DESIGN: The authors conducted a prospective trial of subjects with unilateral deafness in a tertiary care center. PATIENTS: This study comprised adults with unilateral deafness (pure-tone average [PTA] > 90 dB; Sp.D. < 20%) and either normal monaural hearing (n = 18) or moderate SNHL (PTA = 25-50 dB: Sp.D. > 75%) in the contralateral functional ear (n = 5). INTERVENTIONS: Subjects were fit with contralateral routing of signal (CROS) devices for 1 month and tested before (mastoid) implantation, fitting, and testing with a bone-anchored hearing aid (BAHA). OUTCOME MEASURES: Outcome measures were: 1) subjective benefit; 2) source localization tests (Source Azimuth Identification in Noise Test [SAINT]); 3) speech discrimination in quiet and in noise assessed with Hearing In Noise Test (HINT) protocols. RESULTS: There was consistent satisfaction with BAHA amplification and poor acceptance of CROS amplification. General directional hearing decreased with CROS use and was unchanged by BAHA and directional microphone aids. Relative to baseline and CROS, BAHA produced significantly better speech recognition in noise. Twenty-two of 23 subjects followed up in this study continue to use their BAHA device over an average follow-up period of 30.24 months (range, 51-12 months). CONCLUSION: BAHA amplification on the side of a deaf ear yields greater benefit in subjects with monaural hearing than does CROS amplification. Advantages likely related to averting the interference of speech signals delivered to the better ear, as occurs with conventional CROS amplification, while alleviating the negative head-shadow effects of unilateral deafness. The advantages of head-shadow reduction in enhancing speech recognition with noise in the hearing ear outweigh disadvantages inherent in head-shadow reduction that can occur by introducing noise from the deaf side. The level of hearing impairment correlates with incremental benefit provided by the BAHA. Patients with a moderate SNHL in the functioning ear perceived greater increments in benefit, especially in background noise, and demonstrated greater improvements in speech understanding with BAHA amplification.

Comparison of the bone anchored hearing aid implantable hearing device with contralateral routing of offside signal amplification in the rehabilitation of unilateral deafness.

OBJECTIVE: Monaural hearing imposes constraints under many listening conditions. The authors compared the effects of a semi-implantable bone conductor, the Entific bone anchored hearing aid, with conventional contralateral routing of offside signal amplification to assess rehabilitative benefit in adults with unilateral deafness. DESIGN: Prospective trials of subjects with unilateral deafness using benefit surveys, source identification testing, and hearing in noise testing. SETTING: Tertiary referral center, outpatient surgical and audiologic services. PATIENTS: Adults with unilateral deafness (pure tone average >90 dB, SD <20%) after acoustic neuroma excision (n = 7), meningitis (n = 1), sudden sensorineural hearing loss (n = 1), and sudden sensorineural hearing loss with chronic suppurative otitis media (n = 1). Entry criteria included normal hearing in the contralateral ear (pure tone average <25 dB, SD >80%). INTERVENTION: Subjects were fitted with contralateral routing of offside signal amplification devices for 1 month and tested with contralateral routing of offside signal before mastoid implantation of the deaf ear, fitting, and testing for bone anchored hearing aid. OUTCOME MEASURES: Subjects' assessment of experience with their devices and patterns of use, 2) source azimuth identification in noise test, and 3) speech discrimination in quiet and in noise under conditions of noise-front, noise-to-normal-ear, and noise-to-deaf-ear. RESULTS: There was consistent satisfaction with bone anchored hearing aid implantation and amplification, and poor acceptance of contralateral routing of offside signal amplification. Sound localization was poor at baseline and with both bone anchored hearing aid and contralateral routing of offside signal. Relative to baseline, contralateral routing of offside signal and bone anchored hearing aid produced significantly better speech recognition in noise under most conditions. The bone anchored hearing aid enabled significantly better speech recognition than contralateral routing of offside signal in quiet and in a composite of noise conditions. The advantages may relate to averting the interference of speech signals delivered to the better ear, as occurs with conventional contralateral routing of offside signal amplification. CONCLUSIONS: Preliminary data in subjects with normal monaural hearing indicate that vibromechanical stimulation with the bone anchored hearing aid overcomes some of the negative head shadow effects in unilateral deafness. The bone anchored hearing aid system, when placed on the side of a deaf ear, yields greater benefit in subjects with normal monaural hearing than does contralateral routing of offside signal amplification. It seems that this rehabilitative approach can expand the sound field of monaural listeners in further enhancing speech understanding. Observations suggest that further understanding of bone conduction as implemented in transcranial stimulation will guide further options for patients with monaural hearing. Longer follow-up will help to determine whether communicative skill improvements with the bone anchored hearing aid outweigh the disadvantages of implantation surgery, costs, and device maintenance.

Dehiscence of bone overlying the superior semicircular canal as a cause of an air-bone gap on audiometry: a case study.

Dehiscence of bone overlying the superior semicircular canal can result in a syndrome of vertigo and oscillopsia induced by loud noises or by maneuvers that change middle ear or intracranial pressure. Patients with this disorder can also experience a heightened sensitivity to bone-conducted sounds in the presence of normal middle ear function. High-resolution CT scans of the temporal bones demonstrate the dehiscence. The authors describe a patient with bilateral superior canal dehiscence who had bilateral low-frequency conductive hearing loss, normal middle ear function, intact acoustic reflexes, and intact vestibular-evoked myogenic potentials. These findings would not be expected on the basis of a middle ear cause of the conductive hearing loss. A high-resolution CT scan of the temporal bones in this patient revealed bilateral superior canal dehiscence. Normal acoustic immittance findings in the presence of conductive hearing loss should alert clinicians to the possibility of inner ear cause of an air-bone gap due to superior canal dehiscence.

Development of a microportable imaging system for otoscopy and nasoendoscopy evaluations.

OBJECTIVE: Imaging systems for patients with cleft palate typically are not portable, but are essential to obtain an audiovisual record of nasoendoscopy and otoscopy procedures. Practitioners who evaluate patients in rural, remote, or otherwise medically underserved areas are expected to obtain audiovisual recordings of these procedures as part of standard clinical practice. Therefore, patients must travel substantial distances to medical facilities that have standard recording equipment. This project describes the specific components, strengths and weaknesses of an MPEG-4 digital recording system for otoscopy/nasoendoscopy evaluation of patients with cleft palate that is both portable and compatible with store-and-forward telemedicine applications. MATERIALS: Three digital recording configurations (TabletPC, handheld digital video recorder, and an 8-mm digital camcorder) were used to record the audio/ video signal from an analog video scope system. RESULTS: The handheld digital video recorder was most effective at capturing audio/video and displaying procedures in real time. The system described was particularly easy to use, because it required no postrecording file capture or compression for later review, transfer, and/or archiving. CONCLUSIONS: The handheld digital recording system was assembled from commercially available components. The portability and the telemedicine compatibility of the handheld digital video recorder offers a viable solution for the documentation of nasoendosocopy and otoscopy procedures in remote, rural, or other locations where reduced medical access precludes the use of larger component audio/video systems.