title: Amplification in the rehabilitation of unilateral deafness: speech in noise and directional hearing effects with bone-anchored hearing and contralateral routing of signal amplification.
abstract: 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)?
  
  
  METHODS
  The authors conducted a prospective trial of subjects with unilateral deafness in a tertiary care center.
  
  
  METHODS
  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).
  
  
  METHODS
  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).
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, The Johns Hopkins University, Baltimore, Maryland 21287-0910, USA.
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Lin
authors.forename: Stephen
authors.initials: S
authors.lastname: Bowditch
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Anderson
authors.forename: Bradford
authors.initials: B
authors.lastname: May
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Cox
authors.forename: John K
authors.initials: JK
authors.lastname: Niparko
mesh_terms: D000328:Adult; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006310:Hearing Aids; D046088:Hearing Loss, Unilateral / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009622:Noise / Q000009:adverse effects*; D017060:Patient Satisfaction; D011446:Prospective Studies; D013017:Sound Localization; D013067:Speech Perception; D016896:Treatment Outcome