Sound localization in patients with unilateral cochlear implants

To evaluate sound localization ability in totally deaf patients with unilateral cochlear implants and to estimate the ability to improve this function by training.

A controlled case series.

Nine patients with monaural cochlear implants were asked to identify the source of 50 randomly distributed sound stimuli coming from five different directions anteriorly or laterally. After some training, patients were retested. There were two control groups. One comprised nine adults with normal hearing, and the other comprised nine adults with normal hearing but one ear plugged.

The mean initial score of the study group (maximal score 100) was 41.5 (range 23-63). Patients who had used cochlear implants longer had better sound localization ability (Spearman's correlation coefficient = 0.92). On retesting, after an average of 6.3 training sessions, their mean score improved to 66 (range 32-95), (p = 0.008). The improvement was more pronounced in postlinguals than in prelinguals (p = 0.016).

Spontaneous development of sound localization ability in totally deaf patients with unilateral cochlear implants is proportional to the time interval between implantation and initial testing. Improvement appears to be influenced by training, and to be greater in postlingual than in prelingual implantees.