A 3-year-old child was brought to our hospital in September 2017 with a complaint of hearing loss and delayed speech and language skills. To begin with the assessment, a detailed case history was taken. Postnatal history was significant with high bilirubin level which in turn included a 6-day NICU stay. The routine newborn hearing screening suggested bilateral normal hearing. However, with increase in age, the child exhibited reduced response to name call and environmental sounds. Shortly after the birth, the child was diagnosed with hearing loss. Simultaneously, the development of speech and language skills was also hampered.
In concern to this, the parents consulted a specialist in Jordan and performed a detailed hearing assessment which included Tympanometry, Auditory Brainstem Response (ABR) and Auditory Steady State Response (ASSR). Tympanometry showed “A” type tympanogram with absent ipsilateral acoustic reflexes. Diagnostic ABR revealed bilateral profound hearing loss and ASSR indicated bilateral severe hearing loss.
On the contrary, the mother of the child was anxious about the condition of the child. Mother believed that child’s recent uncertain response to name call, environmental sounds, and moderate-severe speech perception difficulties might prove the previously tested reports wrong. Thus, the parents reached SGH to seek the second opinion. SGH Dubai has a dedicated audiology team with Dr. Samer Sakka Amini (ENT specialist) and Ms. Teja Deepak Dessai (Audiologist), who work towards the betterment of people exhibiting hearing and balance related problems and its management.
Our Audiology team began with the non-standardized method such as name calling and clapping at normal loudness levels. The child gave a constant and confirmed head turn response towards the source of sound. This made the team curious to give positive judgment over the mother’s observation. Further, ABR was scheduled post two days to derive a conclusion. Presence of ABR peaks was expected at the beginning of test. However, absence of peaks in ABR testing with presence of CM was discovered. To add on, presence of Cochlear Microphonics (CM) was confirmed by carrying out the same procedure with change in the polarity and presence of CM was confirmed.
At this stage, lower sensitivity and specificity of the test required us to further continue with the test battery approach. Diagnostic Oto-acoustic emission (OAE) was administered and to our expectation, the OAE was present bilaterally. All the test results indicated the presence of AN. It is a rare condition coupled with several other symptoms like reduced speech and language output, fluctuating hearing and poor speech perception difficulty which the child exhibited. Thus, the child was diagnosed with Auditory Neuropathy Spectrum Disorder (ANSD).
Auditory neuropathy (AN) is a term used to describe a type of hearing disorder in which outer hair cell function (the cochlear amplifier) is normal; however, there is a disruption in afferent conduction along the auditory neural pathway. The diagnosis of AN is based on a distinct pattern of audiometric test results, including normal OAE and/or CM, with absent middle-ear muscle reflexes and absent or abnormal ABR.
The range of auditory complaints and auditory difficulties associated with AN is vast and has resulted in the acceptance of the term ANSD to better describe the disorder. A majority of individuals with ANSD have low-frequency hearing loss and/or very poor speech recognition scores for the degree of hearing loss measured through Pure Tone Audiometry assessment. Poor temporal resolution is associated with ANSD, which results in a poor perception of changes in stimuli over time. Speech perception can be adversely affected due to reduced sensitivity to follow fast and slow temporal modulations, reduced the ability to detect gaps in continuous sound, and reduced frequency discrimination at low frequencies. This, in turn, can lead to poor speech and language development skills.
Now, with the labeling of child, management option was highlighted. Firstly, the parents were counseled regarding the pathophysiology of auditory pathway in ANSD. Secondly, the need for environmental auditory modifications to improve the signal to noise ratio (SNR) was explained and thirdly, amplification device and its uses to the child and her development were explained. Fourthly, Cochlear Implantation was suggested to improve the SNR. Overall, Speech therapy and Auditory therapy was also suggested.
ANSD has only a prevalence of 0.23% to 15% in individuals with hearing loss. Therefore, it is rare to encounter ANSD in the hospital setup and may easily go unnoticed or unattended. Hence, it is important to carry out a detailed hearing assessment in a proper clinical setting.
Dr. Samer Sakka Amini (ENT Specialist) & Ms. Teja Deepak Dessai (Audiologist)
SGH Audiology Team