|Year : 2013 | Volume
| Issue : 1 | Page : 6-11
Outcome of auditory neuropathy after cochlear implantation
Abdul Monem Al Shaikh1, Hatem Ezz Eldin2, Alaa Abousetta3
1 Department of Otolaryngology & Head and Neck Surgery. King Fahd Hospital, Jeddah, Saudi Arabia
2 Department of Otolaryngology, King Fahd Hospital, Jeddah, Saudi Arabia; Department of Otolaryngology, Phoniatric Unit, Sohag College of Medicine, Egypt
3 Department of Otolaryngology, King Fahd Hospital, Jeddah, Saudi Arabia; Department of Otolaryngology, Audiology unit S. C. College of Medicine, Egypt
|Date of Web Publication||2-Jan-2020|
MD Abdul Monem Al Shaikh
P.O. Box: 10462, Jeddah 21433
Source of Support: None, Conflict of Interest: None
Purpose: To record language and auditory skills development before and after cochlear implantation (CI) in children with auditory neuropathy (AN), and to determine the outcome after cochlear implant in patients with AN in comparison to patients with sensorineural hearing loss (SNHL).
Material and Methods: Cases Included in this study were divided into two groups. Group I: includes, 13 children diagnosed with AN, 7 of them were subjected to CI. Group II: included 14 cases of SNHL, of them 10 patients were subjected to cochlear implant. For all cases language therapy was given regularly for 6 months pre-operatively and 6 months post-operatively. Auditory Skills Checklist (ASC) and The Arabic language test (receptive, expressive and total language Quotients) were used to monitor the progress concerning auditory skills and language development.
Results: There was significant improvement in SNHL group and AN group after cochlear implantation regarding auditory skills (AS) and language development and almost the same outcome was obtained in both groups.
Conclusions: Cases with AN improved markedly after cochlear implantation and no differences were noticed in outcome between SNHL & AN groups.
Keywords: Hearing loss, auditory neuropathy, cochlear implant, auditory skills
|How to cite this article:|
Al Shaikh AM, Eldin HE, Abousetta A. Outcome of auditory neuropathy after cochlear implantation. Saudi J Otorhinolaryngol Head Neck Surg 2013;15:6-11
|How to cite this URL:|
Al Shaikh AM, Eldin HE, Abousetta A. Outcome of auditory neuropathy after cochlear implantation. Saudi J Otorhinolaryngol Head Neck Surg [serial online] 2013 [cited 2022 Nov 28];15:6-11. Available from: https://www.sjohns.org/text.asp?2013/15/1/6/274645
| Introduction|| |
Auditory neuropathy (AN) is a hearing disorder characterized by normal functioning of outer hair cells, evidenced by intact cochlear microphonic (CM) potentials and outoacoustic emission (OAEs) with absent or severely desynchronized auditory brainstem response (ABRs) . It is much more common than most investigators initially thought. Current incidence of AN is 0.5% to 1.3% of patients attending the audiology clinics .
They account about 12% to 14% of patients having absent ABR. The vast majority of the patients have absent ABR and Wave I is always absent, CM is Present in all cases of AN, OAEs may miss up to 50% of cases ,3.
AN may be caused by hereditary, metabolic, toxic or inflammatory conditions. Hyperbilirubinemia, kernicterus and anoxia are possible factors .
Possible site of lesion:
- IHC and auditory nerve dendrites,
- Spiral ganglion, synaptic junction between IHC and auditory nerve,
- Auditory nerve axons (demyelinated, axonal degeneration). Patients with AN may show poor temporal encoding and degradation of speech perception, ranging from limited to no open-set discrimination .
Starr et al.  reported that patients may show varied SNHL mild to severe and usually bilateral.
Poor speech discrimination, absent or severely abnormal
ABR may also be encountered. They also mentioned that hearing aids, FM systems, tactile aids are seldom of benefit.
The Goals of this study
- To explore development of auditory skills and language development before and after cochlear implantation in children with AN
- To compare the outcome after CI in patients with AN Vs patients with SNHL
Subjects and methods:
This study was conducted on children below 5 years of age presenting to the ENT Center, King Fahd Hospital, Jeddah, from April, 2010 to April, 2011 complaining of congenital hearing impairment and delayed language development.
Patients selected according to audiological evaluation (ABR-OAEs & Cochlear microphonic).Total cases examined during the whole period were 72. The number of cases with auditory neuropathy was 13. The percentage of auditory neuropathy was about 18% of total cases diagnosed with Bilateral SNHL. ALL cases were fitted with the proper hearing aids adjusted according to DSL i/o fitting formula (used regularly)
AN patients fitting followed a flexible way where loudness adaptation was taken into consideration.
All implanted children used MEDEL CI with the implant model Sonata.and processor model OPUS 2.with the ( Fine Structure Processing) strategy used.
All cases included in this study fulfilled the criterion of the aided levels ranging between 40-50 dBHL using hearing aids (preop.) and between 25-35 dBHL using CI (postop.)
Cases included in this study were divided into:
Group I: 13 children diagnosed with Auditory neuropathy, 7 cases subjected to cochlear implant.
Group Π: 14 children were diagnosed with SNHL ten of them were subjected to cochlear implantations. The 14 case were selected to be matched as regards age, gender, IQ and social class.
For all cases language therapy was given in our center three sessions per week regularly for 6 months pre operatively and 6 months post operatively to monitor the progress concerning AS and language development. We followed Auditory training rehabilitation programme elaborated by Erber, N. (1982) (6) and Ross M (2008) (7). They designed auditory training programs for rehabilitation of pre-lingual hearing impaired children which involve:
- Sound detection.
- Sound discrimination.
- Sound identification.
- Sound recognition.
Visual and auditory cues (lip-reading) were used in the beginning of the training with gradual removal of the visual cues. Then auditory cues only were used. The training rooms were quite and furnished by carpets on the ground curtains on the walls to reduce noise for the optimal listening conditions. Noise makers and different materials were used to facilitate training sessions.
Evaluation of the patients:
Phoniatric, audiological and psychometric evaluation were done for all cases immediately after diagnosis, 6 months after language therapy and 6 months post cochlear implant.
Auditory Skills Checklist (ASC) (8): that measures the progress in various auditory skills. The checklist consisted of 35 items representing 4 domains: detection (9 items), discrimination (7 items), identification (7 items), and comprehension (12 items). The check list application was in the form of questionnaire to the parents that sometimes needs confirmation by testing the child in an informal way in the clinic. At the time of administration, each item of the scale was rated as one of the following: does not have skill, emerging skill, and developed skill. These levels of skill were then quantified respectively as 0, 1, or 2. The 35 questions on the ASC were quantified to yield a total possible raw score of 70, with a range of the total score to fall between 0 and 70 (detection = 18 points, discrimination = 14 points, identification = 14 points, comprehension = 24 points). Higher scores reflect higher or more developed functional auditory skills. Children who received a cochlear implant were expected to increase their ASC score by 8 points or more every 3 months. Aided audiometry was done for every patient before, each checkup using Arabic language test and ACS.  The Arabic language test (9) For monitoring the progress in different language parameters by calculating the Expressive Language Quotient (ELQ), Receptive Language Quotient(RLQ), and total language Quotient(TLQ)
Psychometric evaluation: using (nonverbal Wechsler Intelligence Scale for Children–Third Edition, 1991) . All children demonstrated at least normal range of non-verbal Intelligence Quotient (IQ >95). Children with Auditory neuropathy (AN) were 6 boys (46%) and 7 girls (54%) with a mean age of 38 months ± 6 months. Children with SNHL were 7 boys (50%) and 7 girls (50%) with a mean age of 40 ± 8months. Children of both groups were similarly matched by age and IQ.
Analytical statistics was done using Student’s “t” test to compare between two independent groups. Paired t-test used to compare means on the same subjects over time or in differing circumstances. Statistical significance was associated with a P value of less than 0.05.
| Results|| |
No significant differences (P > 0.05) were found between the 2 groups regarding the age, gender distribution and IQ. P >0.05 = Non Significant [Table 1]
|Table 1: Comparison between the SNHL group, Auditory neuropathy group (AN) regarding the demographic data:|
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There was insignificant difference between SNHL group and AN group regarding auditory skills development and different language parameters preoperatively.
No statistical differences were found in both groups after 6 months of regular language therapy
There was highly significant difference regarding auditory skills development. Pre and post operative and post op. Also there was significant difference between pre and post operation and pre and post operative regarding different language parameters. Six cases showed evident improvement concerning auditory skills and different language parameters after CI, One case showed little improvement compared to the other cases.There was highly significant difference regarding auditory skills development. Pre and post operative and significant difference regarding different language parameters. There was insignificant difference between SNHL group and AN group regarding auditory skills development and different language parameters.
| Discussion|| |
Auditory neuropathy is a challenging disorder and needs special rehabilitative approach. AN management aims at restoring the compromising processing of auditory information, either through conventional amplification and/or alternative forms of communication, or by cochlear implantation combined with intensive speech and language therapy. The choice of the ASC for testing the auditory skills was done as some children included in this study were below 3 years of age and in authors’ view most of the children were unable to complete standardized testing protocols. In addition, ASC is generally viewed by clinicians as a quick, practical and reliable measure to monitor the progress after cochlear implant.
In this study we found limited benefit of H.A and amplification for cases with AN, this coincide with the conclusion reached by Shallop et al, (2001) (11) who reported limited success with H.A, FM systems and tactile aids, as the problem of neural dissynchrony is not addressed and even lead to a detrimental effect.
In this study six cases out of seven children implanted showed significant and satisfactory results. They gained more than 16 points in Auditory Skills Checklist (ASC), six months after auditory rehabilitation program.
Evaluation of auditory skills six months post cochlear implant showed that improvement in sound awareness (detection) and discrimination was more evident than identification and comprehension. This may be explained by the limited time frame of the study. It is well known that children first acquire sound awareness and discrimination followed by identification and comprehension.
Shallop et al (11) mentioned that their experiences with cochlear implantation for children diagnosed with auditory neuropathy have been very positive. All of the 5 children implanted have shown significant improvements in their sound detection, speech perception abilities and communication skills. All of the children have shown evidence of good NRT results postoperatively.
Teagle, et al (2010) (12) conducted a study on 70 children who underwent CI. They mentioned that although 50% of the implanted children with AN demonstrated openset speech perception abilities after implantation, nearly 30% of them with >6 months of implant experience were unable to participate in this type of testing because of their young age or developmental delays. Many of these children were born prematurely (42%) and impacted by a variety of medical comorbidities. More than one third (38%) had abnormal findings on preoperative magnetic resonance imaging of the brain and inner ear.
In this study one child failed to achieve significant improvement less than 16 points on Auditory Skills Checklist (ASC) six months after auditory rehabilitation program.
This may be explained by the best that children with AN who receive CIs are a heterogeneous group with a wide variety of impairments. Although many of these children may ultimately benefit from implantation, some will not, presumably because of a lack of electrical-induced neural synchronization, the detrimental effects of their other associated conditions, or a combination of factors.
Many investigators have shown that early cochlear implantation can be of benefit for some children with AN. ,,. In this study we found that most cases (6 out of 7) with AN improved markedly after CI concerning auditory skills and language development, this may be explained by the fact that electrical stimulation of the cochlea is better than acoustic stimulation for AN cases. Also, electric stimulation via a cochlear implant produced significantly higher intelligibility than acoustic stimulation. Simmons et al; (2000)(16) mentioned that CI promotes neural survival, restores temporal encoding, produces synchronous ABRs in the presence of peripheral nerve demyelination and they recommended CI for selected cases of AN.
Although the present results support cochlear implantation as one treatment choice for subjects with AN, success in implantation may depend on the site of the pathology.
In this study, no significant differences were noticed in outcome between SNHL & AN groups after Cochlear implant. Many authors proved benefit of subjects with SNHL after cochlear implantation. This can be understood under the notion that cochlear implant substitutes the function of the lost cochlear amplifier and transducer, namely outer hair cells. On the other hand, participants with AN most likely derive the clear speech advantage from enhanced temporal fidelity and improved neural synchrony with electric stimulation.
| Conclusion|| |
- Cases with AN improved markedly after cochlear implantation. We should elaborate about the choice of the cases with good thickness of the auditory nerve in MRI.
- No significant differences were noticed in outcome between SNHL & AN groups.
- Future study to examine the validity of the well established protocol which includes waiting for 6 months preoperatively in AN cases.
- More research work needed with big number of cases with long period of follow up [Figure 1] [Figure 2] [Figure 3] [Figure 4]
|Figure 1: Comparison between the two groups regarding preoperative AS and Language development.|
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|Figure 2: Comparison between preoperative AS and postoperative AS and Language development of AN group|
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|Figure 3: Comparison between preoperative and postoperative AS and language development of the SNHL group|
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|Figure 4: Comparison between the two groups regarding Postoperative. AS and Language development|
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]