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Online EHDI Case 5 (Part 2 With Answers)

Online EHDI Case 5: A NICU Graduate with Neural Hearing Loss

Part 2

Samantha who is now 4.5 months old returns with her parents per your request to discuss the outcome of her audiologic evaluation, which was conducted 1 week ago. The audiologist who conducted this evaluationcalled you and mailed a copy of the results which are as follow:

Right/Left ear:
    Tympanometry: Normal
    OAEs: Present across frequency range
    ABR: No response

You have asked the family to come see you to further discuss the audiological results and help the family have the appropriate referrals.

______________________________________________________________

1. How do you interpret Samantha’s Audiologic results?

 Peripheral hearing is normal (OAEs present) but the signal is not being sent through the auditory pathway as demonstrated by the ABR results. Samantha has a bilateral neural hearing loss (Link to http://www.babyhearing.org/HearingAmplification/Causes/Neuropathy.asp) oftentimes referred to as auditory neuropathy/dys-synchrony or AN/AD. This is different than sensorineural hearing loss (SNHL), which implies a dysfunction of the cochlea. That is, most hearing losses that are described as sensorineural have a problem with the sensory cells, i.e. hair cells of the inner ear (or cochlea). In cases of neural hearing loss, the sensory cells are intact and functioning, but the nerve is not able to transmit the signal to the brain. The broader term, sensorineural, is typically used because it cannot always be distinguished if it is a sensory issue, a neural issue or a combination of the two.
 Additionally, we would like to caution you that the term “auditory neuropathy/Dys-synchrony” has been mistakenly used interchangeably with the term “neural hearing loss”. The distinction between the two terms has been clearly described by Rapin & Gravel, 2003 (link to … Rapin, I. and Gravel, J. (2003) “Auditory Neuropathy”: physiologic and pathologic evidence calls for more diagnostic specific. International Journal of Pediatric otorhinolaryngology. 67, 707-728.…) who state that “the term auditory neuropathy should be reserved for patients in whom there is evidence that the pathology involves the spiral ganglion cells or their axons (8th nerve)”. The term of auditory neuropathy should NOT be used when the main site of pathology is in the brainstem or more centrally in the auditory pathway. The term neural hearing loss should be used then….for “cases where predominance of the hearing loss is in the spiral ganglion cells or the central nervous system (brainstem, thalamus and cortex)”. In order for this
distinction to be made, the patient has to undergo additional testing and therefore, unless these further tests have been conducted, we urge you to use the term “neural hearing loss” rather than auditory neuropathy/Dys-synchrony.
 Neural hearing loss is a hearing impairment involving the disturbed neural conduction along the auditory pathway. With neural hearing loss, outer hair cell function is normal, as evidenced by normal responses to audiologic tests that measure cochlear function (OAEs). With neural hearing loss, the underlying abnormality could come from multiple sites of lesion such as inner hair cells (IHCs) the synapse between the IHCs, and the auditory nerve and its different structures, and characterized by an abnormal ABR.
 Prevalence of the disorder remains questionable with the reported rate of occurrence ranging from as low as 0.5% of the hearing impaired population to as high as 15%. (Rance, G. (2005) Auditory Neuropathy/Dys-synchrony and its perceptual Consequences. Trends in Amplification. Vol 9-1; 1-43)
Both genetic and environmental factors are known to cause neural hearing loss, and it has been diagnosed in 10%-15% of the deaf population and 40% of babies in NICUs.
 When a child has a neural hearing loss, behavioral audiograms (when reliably obtained) can range from normal/mild to profound in severity. While pure tone testing could at times reveal a mild loss, many of those patients will have difficulty’s interpreting speech signals (especially in the presence of background noise). For a child, this is a crucial finding. When Samantha is older, around her first birthday, behavioral testing will be conducted.

2. What happens next?

 First, ensure that the family understands the implication of this hearing loss and the importance for action in getting Samantha the services she needs. Do they have any questions about the diagnosis itself? The audiologist should have explained it to them; however it is not easy for parents to understand the complexity of this disorder especially when the family is so emotionally involved. Therefore, it is always crucial to ensure that the family understands the diagnosis and the subsequent habilitation which will be a life-long endeavor.
 It is reasonable for you not to be able to answer all of the families’ specific questions about this hearing loss; however, it is extremely important that you are able to identify their concerns and direct them to the audiologist or other professionals. As a key component of the child’s Medical Home, you need to maintain good and effective communication between the family and the other specialists who will be involved in Samantha’s medical care.
 Samantha needs to start habilitation right away
        o On-going audiologic re-evaluation
 Due to the young age at which most hearing losses are currently being identified, it is not unusual to need repeat testing to ensure that there are, or are not, changes in hearing over time; often, a definite etiology of the hearing loss is not known, or when it is known, many reasons for hearing loss in children can cause change (e.g. progression of the hearing loss).
        o Referral to early intervention services is essential. This should have been done by the audiologist but a discussion about early intervention services (link to http://www.babyhearing.org/LanguageLearning/EarlyIntervention/index.asp) may again clarify the need for the services.
        o Per JCIH 2007 (link to: http://www.pediatrics.org/cgi/content/full/120/4/898), children identified with hearing impairment should be referred for medical workup to include otology, genetic and ophthalmology evaluation to determine the possible etiology of the disorder and possible associated medical conditions. Therefore, a referral to a pediatric otolaryngologist is needed. It is also important to notice that the incidence of neural hearing loss (Link to http://www.babyhearing.org/HearingAmplification/Causes/Neuropathy.asp) is more common in patients who stayed in the NICU, especially those with persistent pulmonary hypertension of the newborn (PPHN); severe hyperbilirubinemia level; extremely low birth weight (ELBW) babies; severe asphyxia; neurodegenerative disorders. Due to the diversity of etiologies, sites of lesion and auditory abilities associated with this disorder, remediation is quite challenging for this group of individuals.
 Both family and clinicians need to be prepared to explore multiple options for intervention including amplification, different modes of communication and cochlear implantation. What works for one child, may not work for another one. So this might take many trials before a solution is found to benefit the child. However, given the significant negative impact of background noise on the speech understanding for these individuals, personal FM technology should always be considered regardless whether a child utilizes a hearing aid or a cochlear implant Good communication between the PCP, audiologist, early intervention specialists and family is very important to help ensure the best outcome for these children. Please refer to the following resources for an indepth look at remediations/management of children with neural hearing loss.

NIDCD Auditory neuropathy. Link to: http://www.babyhearing.org/HearingAmplification/Causes/Neuropathy.asp

o Rapin & Gravel, 2003- p 724-725. Rapin, I. and Gravel, J. (2003)
“Auditory Neuropathy”: physiologic and pathologic evidence calls for
more diagnostic specific. International Journal of Pediatric
otorhinolaryngology. 67, 707-728.

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