5|DISCUSSION
In clinical practice, children with LVAS always were such a group attracting our special care and attention, not only because of fluctuated hearing level, but also balance problems(3,4). While, were there any differences in development level between LVAS subjects and children without LVAS? In order to solve the problem, we selected the specific two groups: children with LVAS and without LVAS but with the same hearing impairment, and compared the performance between the two groups, particularly discussing motor development in-depth.
Our study showed developmental retardation both in LVAS children and non-LVAS children. The retardation not only occurred in verbal development but also in non-verbal developments. Through the grading the developments, we found that the majority of children in this study had mild neurological damage. Of all sub-developments, language developed worst and motor developed best. According to the results, developments of deaf children were worthy attention. Of note, the children in our study were the group with sever or profound hearing loss. Thus the developments in our study could not represent the whole performance of the group with hearing impairments, because the hearing level was associated with the developments revealed in previous research (24-26).
In previous literatures, delayed ambulation and poor coordination in LVAS children were reported(8,10,11), which was consistent with our above findings. Prior to foregoing study, we evaluated more comprehensively including the gross motor such as sitting, walking and balance ability, and fine motor such as grabbing, pitching and coordination ability. In this study, compared with normal developmental criteria, LVAS children had developmental delay in gross motor, while non-LVAS children had the normal performance in gross motor. For the children with LVAS, a special group of hearing impairment, were their developmental level different from the other deaf children? To addressed the question, we compared the performance between the two groups and didn’t found any significant difference including gross motor.
Although vestibular weakness have been marked in LVAS patients in previous study(3,4), while motor retardation and disbalance of LVAS children in our study couldn’t be concluded caused by vestibular disorder. According to our study, we could only describe such a phenomenon and couldn’t conclude whether the vestibular dysfunction induced by LVAS has effects on development, of which the reasons could be summarized as follows. Firstly, the progress of hearing loss in LVAS patients was fluctuate(27), whereas the hearing thresholds of LVAS children in our study tend to their worst hearing level because they were candidate to cochlear implantation in our hospital. So, the hearing threshold couldn’t represent the real average auditory level of LVAS children. Secondly, the age of hearing loss occurring, the duration of disease, and the usage of hearing aids, which might affect the developments, weren’t normalized. Last but not least, although the LVAS patients were with high rates of vestibular dysfunction, the children with abnormal vestibular test results might not appear vestibular symptoms (8). In addition, balance ability were affected not only by vestibular consciousness but also by vision and proprioception(28). When one of them was damaged, the other functions would form compensation(29).Therefore, longitudinal follow-up study, vestibular tests, more evaluation specially for motor and balance should be adopted to address these issues.
In the clinical practice, regardless whether the vestibular dysfunction caused by LVAS had additional effects on developments, the phenomenon that there was no difference in developments between the two above groups was a great news for us. If so, we didn’t pay extra attention to the developments in LVAS, compared with the other deaf children. Meanwhile, we could focus on the prevention to hearing deterioration in LVAS children and the search of good intervention methods after hearing impairments occurred.
Our study also found that age of intervention was the negative related factors for developments except fine motor. Thus, we further compared the developments among the different age group and found that the delay appearance infancy (6-12 months) to toddler (12-36 months) stage, whereas the developmental levels of the toddler and preschool (36-72 months) stages were no obvious difference. So, we could say that the delay started from the 1-year-old, which suggesting that the intervention should be performed before 1- year-old. Until now, hearing aids and cochlear implantation have been effective approach for increasing auditory perception(1,30,31). According to previous literature that intervention as soon as possible could improve the prognosis of hearing-impaired children(32,33). Moreover, children with LVAS undergoing cochlear implantation did well audiometrically and functionally as other deaf children without LVAS(34,35).
Considering the variety of hearing performance in LVAS children, we paid particular attention to the difference between binaural hearing. Of the LVAS subjects in our study, the mean difference between binaural hearing was more than 10 dB nHL with more than half of asymmetric hearing loss rates. Individuals with asymmetric sensorineural hearing loss have reported discomfort in daily living, both audiologically and psychosocially due to poor localization of sound and poor speech recognition in noise(36-38). whether would the asymmetric hearing loss affect the development of children especially the motor development? Then, we include the symmetry of the binaural hearing as a potential related factor. Through the analysis, we found that no matter the value of difference between binaural hearing or the symmetry couldn’t affect the developments of LVAS children, including the motor development. Owing the children in our study were all with sever or profound hearing loss, it’s possible that the influence from the symmetry was covered up by the effects from auditory deprivation
As potential limitation we have stressed in the article, this study was a cross-sectional study and vestibular function wasn’t been evaluated in this study. So, whether vestibular function affected development of children couldn’t be deduced. In addition, the age of hearing loss occurring and diagnosis, the duration of disease, and the usage of hearing aids, which might be the important factors for developments weren’t into use in this study. Longitudinal follow-up study, professional evaluation specially for motor, balance vestibular tests, and vestibular function, and fully integrated information, should be adopted to address these issues. Of note, both objective and subjective evaluation on vestibular function were difficult to perform on young children, especially on deaf children. While, some scale such as Gesell development schedule adopted in this study was an effective and feasible method to evaluate performance of deaf children, which was further beneficial to formulate intervention strategy of cochlear implantation and rehabilitation strategy.