Risk factors for loss of ipsilateral residual hearing after hybrid cochlear implantation.

OBJECTIVE

Residual low-frequency acoustic hearing benefits cochlear implantees in difficult listening situations such as understanding speech in noise and music appreciation. Most subjects retain functional residual hearing in the operated ear. A small number of patients, however, will lose significant ipsilateral residual hearing after short-electrode cochlear implantation. The objectives of this retrospective series are to determine whether predisposition to hearing loss after implantation exists in a subset of patients and to assess the functional impact of this hearing loss on clinical measures of combined electric and acoustic hearing.

STUDY DESIGN

Retrospective case series.

SETTING

Multicenter clinical trial; tertiary care facility.

PATIENTS

Hearing preservation cochlear implant recipients.

MAIN OUTCOME MEASURE

Frequency-averaged ipsilateral hearing loss at 1 year after activation.

RESULTS

Eighty-five patients from the Hybrid S8 FDA trial had serial postoperative audiometric measurements. Twenty-two of these patients, implanted at the home institution, provided additional medical data. Univariate analysis (Pearson's, Spearman's, Student's t test) showed that the severity of hearing loss at 1 year after activation was significantly correlated with age, male gender, and noise-induced hearing loss as the etiology of hearing impairment. A multivariate regression model corroborated these variables. No other medical factors were predictive. Clinical measures of speech perception (Consonant-Nucleus-Consonant and Hearing in Noise Test) worsened with hearing loss in ipsilateral but not bilateral listening conditions.

CONCLUSION

Age, male gender, and a history of noise-induced hearing loss correlate with the severity of hearing loss at 1 year after activation. Even the most severely affected patients benefit from bilateral electric and acoustic inputs.