人工耳蜗植入对单侧感音神经性聋患者声源定位的影响

Effect of cochlear implantation on sound localization for patients with unilateral sensorineural hearing loss

通过Medline以cochlear implantation AND single-sided deafness和cochlear implantation AND unilateral deafness为关键词进行检索,共纳入12篇文献,评估人工耳蜗植入（cochlear implantation,CI）对单侧感音神经性聋（unilateral sensorineural hearing loss,USNHL）患者声源定位能力的影响.回顾发现,90％ （45/50）的USNHL患者在CI后声源定位能力显著提高,即可以从双耳优势中获益.CI＋正常听力耳（NH）的双耳优势需要听觉经验方可显现,少数患者（30％）在CI开机后3个月就表现出双耳优势,而大部分（90％）患者会在开机6个月时声源定位能力显著提高,开机9个月时患者声源定位能力均有提高.USNHL患者CI＋ NH模式水平方位角定位主要依赖耳间强度差.USNHL发生年龄越小,听觉中枢可塑性越强,听觉剥夺后导致患侧听觉通路退行性变及健侧的适应性增强也越明显.同样,USNHL持续越久,患侧的听觉剥夺及健侧的适应性增强也会越明显.适应性增强的健耳会利用其完整的耳廓波谱信号辅助提高水平方位角定位.同时,患侧的听觉剥夺会使CI后患侧对应通路的再重构受限,增加CI后声源定位改善不理想的风险.因此,USNHL患者因尽早行CI以便获得良好的双耳听觉优势.

The aim of this review was to examine the current literature regarding application of cochlear implantation on patients with unilateral sensorineural hearing loss （USNHL） for improvement on sound localization. The literature were searched in the PubMed database with ‘cochlear implantation AND single-sided deafness＇ or ‘cochlear implantation AND unilateral deafness＇ as keywords. The publication date of the articles was up to 2015-2-12. A total of 12 articles were included. The results show that the ability of sound localization for most of the USNHL subjects （90%） with cochlear implantation was significantly improved than that without CI, which suggests that CI is a superior auditory rehabilitation treatment than BAHA and CROS hearing aids for patients with USNHL, because of the re-establishment of the benefits of binaural hearing. In addition, the benefit of CI for USNHL requires a period of auditory experience or training. About 30% subjects showed significantly improvement on sound localization ability after CI worked for three months. For most of the patients （90%）, the sound localization ability improved after CI worked for six months. When CI worked for nine months, all the subjects would show improvement on sound localization ability. Sound localization of the USNHL subjects with a CI is based primarily on interaural level differences （ILD） while interaural time differences （ITD） provide little advantage or probably not perceptible at all. The younger subject suffers from USNHL, the stronger the plasticity of the auditory center shows, which results in more obvious degeneration of the affected side and adaptive enhancement of the contralateral side of the auditory pathway. Similarly, the longer duration of USNHL lead to more obvious degeneration of the affected side and adaptive enhancement of the contralateral side. An adaptive enhancement of auditory pathway corresponding to the healthy ear will rely more on the monaural spatial cues that available to the intact ear to improve the sound localization in the horizontal plane. Contrarily, the degeneration of auditory pathway corresponding to the USNHL may be limited to re-reorganize from auditory deprivation even after CI, which may increase the risk that a few subjects cannot re-establish the binaural benefits after CI. Therefore, patients with USNHL should accept CI as soon as possible to obtain good binaural benefits, especially for sound localization.