Unraveling Auditory Neuropathy Spectrum Disorder

Introduction

The condition that affects the hearing ability of a person is known as Auditory Neuropathy Spectrum Disorder (ANSD). Even though sound penetrates the inner ear normally, relaying of these signals from the inner ear to the brain does not occur properly. This results in poor abilities to perceive speech and the loss of hearing that ranges from mild to severe (Harrison et al., 2015). ANSD is a rare condition that affects all ages right from childhood to adulthood and can be related to neurological disorders like Ehlers-Danlos syndrome, Friedrich ataxia, Charcot-Marie-Tooth syndrome and Steve-Johnson syndrome (Shaia, 2017). Research has not proven the exact cause for the condition though there are proposals that it could be due to the inner ear hair cells being damaged, auditory nerve damage, poor connections between the auditory nerve and the hair cells and/or a consolidation of these anomalies (Thompson et al., 2001). Understanding and addressing these complexities is essential, particularly for those seeking healthcare dissertation help to explore the impact and management of such conditions.

Some of the predisposing factors to ANSD are health issues that precede parturition such as low supply of oxygen during birth, jaundice, deficiency of dietary thiamine, congenital abnormalities of the brain, premature birth and a low birth weight. In addition to these, medications used during pregnancy or for new born babies may injure the inner hair cells of the baby leading to auditory neuropathy (NIH, 2017). Age related loss of hearing may also cause adults to develop the condition (Moeller et al., 2007). Mutations in the genes that constitute the ability of the ear to relay sound information to the brain predisposes one to the ANSD condition through inheritance of the mutated genes. Almost 40% of the ANSD cases have a genetic origin (Machaiah et al., 2011).

Hearing loss at birth that goes unidentified can have an adverse effect on the development of speech and language, social-emotional advancement and academic achievement in a child (JCIH, 2007). Diagnosis of ANSD is done through a combination of methods like the Otoacoustic emissions (OAE) and the brainstem response (ABR). The indication of ANSD is a normal reading of OAE alongside an anomalous reading of ABR. The normal OAE reading signifies that the outer hair cells are functioning normally (Harrison et al., 2015).

The etiologies of ANSD are very wide in range and, therefore, result in patient groups that are heterogenous. Each of the patients have to be managed individually and methodically for optimal developmental and communication progress. Treatment of ANSD is meant to enhance hearing and highly depends on the austerity of the problem (Shi et al., 2012).

Interventions to ANSD

The management of an ANSD infant needs an approach from a multidisciplinary team, who works alongside the family. It is recommended that the team comprises a Speech- Language Therapist, a Pediatric Audiologist, a medical professional (Paeditrician, an Audiological Physician or an ENT Consultant), a Neurologist and a Teacher of the Deaf (BSA, 2019). The desires of the family and the individual case determine the necessity of involvement and the timing of the professionals (Moeller, 2000).

At one month of age, a baby is screened for hear loss, at three months of age, the presence of hearing loss is confirmed and at six months of age, enrollment of a child for early interventions programs is done. This is the “1-3-6 rule” for National Early Hearing Detection and Intervention (EHDI) goals (NIDCD, 2017). This provides a reasonable line to begin audiological diagnosis and intervention. The time lines ought to be vigilantly adhered to whenever possible, by audiologist, putting into consideration process of grieving for families who have a newborn diagnosed with hardness of hearing of deafness (Daneshi et al., 2018). At times, the 1-3-6 rule is not adhered to probably because of finances, parental anxiety, medical complications of the child and parental unrest due the hear loss diagnosis of their child (Shi et al., 2012).

The desires and needs of a family, to a great extent, determine the modes of communication, putting into consideration the monitored progress of the infant. For most of the infants with ANSD, it is appropriate to use a combination of systems of communication that consolidate visual support. For example, aural/auditory with natural gesture and lip reading, sign language and total communication. On the flip side, an auditory-only mode of approach, for instance, an auditory-verbal therapy, might be unsuccessful (BSA, 2019).

It is very essential to have continuous medical and neurological assessment. Some children could already be having a confirmed diagnosis of a neurological disorder. In others, identification of ANSD in newborn babies through audiological screening could be the first signal of a hidden neurological condition. Therefore, it is highly recommended to have all infants diagnosed with ANSD undergo assessment and investigation by an experienced and skilled pediatrician, pediatric Neurologist or an Audio vestibular physician (Han et al., 2017). The diagnosis of an underlying etiology dictates the most convenient management to be taken, which includes specific interventions if pointed out (Cardon, 2013).

Once a pediatric audiologist identifies a hearing loss, there should be immediate referral of the child to early intervention services. Even though further audiological testing may be required to find out particular threshold of hearing, there should be no lagging in recommending the family and the child to the EHDI team (JCIH, 2007)

Even though ANSD has no known cure, assistive listening devices (ALDs) aid children make sense out of sounds and build their skills in language and communication. For the devices to be fully effective, it has to be accompanied by constant therapy that is conducted by a speech-language pathologist; helps children who are hard of hearing build hearing and speaking skills. ALDs include; hearing aid, frequency modulation (FM) system and Cochlear implant (Thompson et al., 2001). The cochlear implant is a viable option for infants with ANSD (Daneshi et al., 2018)

Children diagnosed to have ANSD should be recommended to a cochlear implant center for evaluation as soon as significant concerned are raised regarding behavioral reactions to sound and development of communication/language/speech. A majority of cochlear implant centers highly advocate for early contact to begin communication for input and advice. A recent report by Nothern (2008) showed that the ultimate decision to install a cochlear implant should be withheld until results from the audiological tests are stable and indicate an indisputable proof of permanent ANSD. These tests can, however, be done as part of the assessment for cochlear implantation in order to avoid delays. According to Han et al., (2017), in cases where the ANSD is highly suspected to be caused by genetic mutations then referral and implantation should be done in a similar time frame to children with serious typical cochleae hearing loss.

According to Cardon et al. (2013), the suitable timeframe for intervention for infants with ANSD that obtain the cochlear implantation is around two years of age.

In addition to ALDs, learning visual communication skills highly benefits children with ANSD condition (Shi et al., 2012). Some of the techniques for visual communication are Cued Speech, American Sign Language and Signed Exact English (Yoshinaga et al., 1998).

According to Moeller (2000), it was proved that involvement of the family and the age of enrollment to intervention programs for their child highly increased their learning scores to a higher extent. The question of whether late-identified infants would catch up after the commencement of the invention services was answered by results of these study showing that late enrollment, to some extent, can be buffered by the family being strongly involved.

Previous reports have demonstrated that there is a lapse in communicating information to families concerning hear loss, hence it causes an enormous delay in initiating early intervention services (JCIH, 2007). This is further aggravated by the absence of incorporated tracking and data management systems and a deficit of facilities and experienced personnel with the expertise and experience required to implement follow ups for children who have been recommended from newborn screening programs (D’Agostino & Austin, 2004).

Little is known about the interventions for unilateral ANSD in young children. Unilateral Sensorineural Hearing Loss (SNHL) effects are not well understood, but the effects on educational progress and language or speech differs among various individuals. The effects, also, of ANSD are not understood fully, hence, monitoring of hearing, development of speech and language and communication are very crucial (Nothern, 2008)

Mohammadi et al. (2015) recommended that infants who have ANSD that is unilateral to get medical referral for aetiological investigation. Currently. The prevalence for cochlear nerve deformities is high in unilateral ANSD patients although not all incidents occur with an ANSD phenotype.

There should be proper monitoring for communication development in infants who display transient ANSD, for a couple of months until, at least, they reach the age of school going. It is highly recommended that there be annual monitoring by Audiologists, if no concerns arise (Uus, 2017).

ARGUMENT

The Joint Committee on Infant Hearing (JCIH, 2007) advocates for a prompt detection of and intervention for newborns with hearing loss. The aim for EHDI is to boost literacy improvement and linguistic proficiency for children who are hard of hearing or deaf. In the absence of suitable opportunities to learn a language, children who are hard of hearing or deaf might lag behind their hearing fellows in cognition, communication, social-emotional advancement and reading. This will lead to lower levels of education and employment opportunities in adulthood (Fortnum et al., 2001).

The figure 1. Above depicts that enrolling a child early to learning interventions programs has a positive impact in the vocabulary scores at the age of five years. Children who were enrolled early, constantly scored better and had favorable performances as opposed to children enrolled at a later stage, despite the level of family support given (Moeller, 2000).

Ching et al (2013), conducted in Australia, a large cohort study of 451 infants who had been diagnosed with childhood hearing impairment that was permanent and were being managed in accordance with their national protocols. Out of the 451, 44 had Auditory Neuropathy Spectrum Disorder. Results depicted that delays in cochlear implantation had a very major impact in global outcomes (language and speech, social and functional measurements). This impact was not apparent for aids of hearing. The report suggested that all the children had gotten amplification before three years of age. The results, therefore, likely imply that the auditory deprivation length is harmful to social outcomes and speech in infants with ANSD, who are cochlear implants candidates.

However, interventionist face a challenge on how to recognize the cases that are inclined to benefit from cochlear implants sooner and how to exclude transient ANSD before the implantation of the cochlear (Cardon et al., 2013). .

According to the JCIH (2007), there is enormous amount of literature that proves the success of early detection and intervention before the age of six months, whereby the involved infants perform 20 to 40 percentile points more on school related measures: articulation; vocabulary; intelligibility; behavior and social adjustment. Therefore, in accordance with the federal guidelines, once a child is confirmed for hearing loss of any degree, a recommendation should be made for an early intervention program withing two days of the confirmation of hearing loss (JCIH, 2007)

CONCLUSION

There have been cases where children diagnosed with Auditory Neuropathy Spectrum Disorder have improved and within a year, begun to hear and speak. In other cases, the children diagnosed with the same have stayed the same, while some of them worsen, showing signs of degeneration of the outer hair cells (Abnormal otoacoustic emissions) (Daneshi et al., 2018). Therefore, in children with ANSD, hearing can get worse or better, remain the same or worsen gradually, depending on the underlying cause or time and methods of intervention

It is crucial for hearing loss to be identified early enough in a newborn in order to give the parent the opportunity to make necessary decisions for the deaf child at a tender age. From the above argument, it is clear that late interventions to infants identified with ANSD causes more harm as opposed to early interventions.

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REFERENCES

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Yoshinaga-Itano C, Sedey AL, Coulter DK, Mehl AL. (1998). Language of early- and later-identified children with hearing loss. Pediatrics; 102: 1161–71.

Ching T.Y.C., Day J., Dillon H., Gardner-Berry K., Hou S., et al. (2013). Impact of the presence of auditory neuropathy spectrum disorder (ANSD) on outcomes of children at three years of age. International Journal of Audiology, 52, S55-S64.

Moeller MP, Tomblin JB, Yoshinaga-Itano C, Connor CM, Jerger S. (2007). Current state of knowledge: language and literacy of children with hearing impairment. Ear Hear;28(6):740-53.

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Manchaiah, V. K. C., Zhao, F., Danesh, A. A., & Duprey, R. (2011). The genetic basis of auditory neuropathy spectrum disorder (ANSD). International Journal of Pediatric Otorhinolaryngology, 75, 151-158.

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Shi, W., Ji, F., Lan, L., Liang, S., Ding, H., Wang, H., Li, N., Li, Q., Li, X., & Wang, Q. (2012). Characteristics of cochlear microophonics in infants and young children with auditory neuropathy. Acta Oto-Laryngologica,

D'AGOSTINO, J.A. and Austin, L., (2004). Auditory neuropathy: a potentially under-recognized neonatal intensive care unit sequela. Advances in Neonatal Care, 4(6), pp.344-353.

Daneshi, A., Mirsalehi, M., Hashemi, S.B., Ajalloueyan, M., Rajati, M., Ghasemi, M.M., Emamdjomeh, H., Asghari, A., Mohammadi, S., Mohseni, M. and Mohebbi, S., (2018). Cochlear implantation in children with auditory neuropathy spectrum disorder: A multicenter study on auditory performance and speech production outcomes. International journal of pediatric otorhinolaryngology, 108, pp.12-16.

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ABBREVIATIONS

ANSD- Auditory Neuropathy Spectrum Disorder

BSA – British Society of Audiology

EHDI- Early Hearing Detection and Intervention

OAE- Otoacoustic Emissions

ABR- Brainstem Response

FM- Frequency Modulation

ALD- Assistive Listening Device

SNHL - Unilateral Sensorineural Hearing Loss