Management of Congenital Deafness in Children

Abstract

Congenital and pre-lingual deafness has a significant impact on language acquisition and the educational process in children. The rehabilitation process must begin as soon as possible.

Restoration of profound sensorineural hearing loss is possible using cochlear implants which are recognized worldwide as the standard treatment. Cochlear implantation in congenital deafness is the best when is performed as early as possible. Late implantation in prelingual deafness does not lead to speech understanding and includes difficulties in auditory tasks. Brain plasticity seems to have an important role in language development in relation to hearing deprivation. To obtain a near to normal development of the congenital deaf child early intervention is mandatory and this is possible when coherent health policies exist for diagnosis and appropriate treatment. This can have a major impact on the development and social integration of the child.

 

Table of Contents:

1. Introduction

2. Anatomical factors

3. Functional factors

4. Brain plasticity and neural competition

5. Management of congenital profound deaf child

6. Conclusions

 

1. Introduction

Deafness is a serious sensory deficiency. Congenital and pre-lingual deafness has important and unfavourable consequences on the psychological maturation of the child, on the evolution of language acquisition, on the educational process as a whole and as well as on his/her subsequent social insertion [1, 2, 3]. Having a decisive importance, early identification of hearing loss [4] will allow early rehabilitation treatments which consist in hearing aids recommendation [5] and inclusion of the child in speech rehabilitation programs.

Currently, in our country, the average age at which hearing impairment is diagnosed is usually after 4 years.

The goal of the rehabilitation process is to begin the treatment of deaf a child well before the age of 2 years and, in short term, it is desirable to be able to start this rehabilitative program before the age of 6 months [6]. For this, it is necessary first of all to initiate an early detection program for deaf children – possibly by introducing a universal new born screening program nationwide.

To understand the need for early treatment of hearing loss, we will briefly discuss some basic notions of anatomy and physiology that impose the particularities of the treatment of hearing loss in the child.

 

2. Anatomical factors

Anatomical factors have a huge implication in ear surgery in children that might benefit from implantable hearing aids. The phylogenetic importance of the ear is demonstrated by the precocity of the appearance and the complexity of its development. Middle ear: the tubo-timpanic recess from the middle ear develops from an endodermic diverticulum of the dorsal segment of the first pouch. The embryonic ossicles develop from the arches I and II (the maleus – from Meckel cartilage and the stapes and part of the incus are formed from Reichert cartilage).

The musculo-ligament apparatus is developed from the mesenchyme of the first and second arch. Inner ear has a double origin: ectodermal for the membranous labyrinth and mesodermal for the bone labyrinth. In the 4th week, from the ectoderm and the lateral part of the rombencephalus, the otic plate is formed from which the otic vesicle will develop.

Neurosensory epithelium is formed under the induction of neuroblasts in the Scarpa and Corti nucleus, activated by neural crests. The inner ear and the auditory nerve are functional from the 4th month of life. The auditory nucleus of the cerebral cortex is functional from the 7th month of intrauterine life. Temporal bone grows continuously until the age of 18-20 years, but the most significant changes in the development, number and configuration of mastoid cells occur until the age of 2 years.

 

3. Functional factors

The external and the middle ear conduct the sound to the cochlea. Lesions at this level produce conductive deafness (9.55% of 1/1000 children with severe bilateral hearing loss) [7].

This type of hearing loss may benefit from surgical treatment (transtympanic tubes, tympanoplasties or implantable or conventional hearing aids). The inner ear (hair cells) – transforms the mechanical energy into electrical impulses. The lesions at this level produce sensory hearing loss (approximately 2% of congenital profound deafness cases are due to cochlear nerve deficiency) [8]. Sensorineural hearing loss is treated with hearing aids or cochlear implants and speech rehabilitation.

 

4. Brain plasticity and neural competition

Plasticity is the ability of the brain to organize itself according to the type of received stimuli. Brain is the organ of behavior, the most important aspect of behavior being the learning process (change in behavior as a result of experience).

The brain is responsable for our ability to hear and also for our ability to acquire language, social communication, appreciation of music, etc. Brain development is achieved progressively, with precise temporal sequences characteristic of each neural entity and each system, through neuronal connections in the brain and neuronal differentiation.

In recent years, many studies have brought to light a series of notions that have improved our understanding of brain physiology, including: brain plasticity and neuronal competition. In children, auditory deprivation leads to delayed or abnormal development of the central auditory pathways, particularly if deprivation occurs during a sensitive period, or an established time window of approximately 3.5 years during which alterations in sensory input (e.g. deafness or hearing loss) can lead to profound and long-term impacts on the brain. [9, 10]. If auditory deprivation continues beyond the sensitive period, the connectivity within the auditory system is disrupted resulting in significant deficits in brain and behavior (e.g. working memory, executive functioning etc.) [11]. Cross-modal re-organization by vision is one form of the changes that take place in cortico-cortico connectivity and was observed in congenital or pre- lingual onset of deafness. [12, 13]

Restoration of profound hearing loss is possible using cochlear implants both in acquired [14] and congenital deafness.

Cochlear implants are recognized worldwide as the standard treatment for profound hearing loss. It is important, during the surgery, to preserve as much as possible the delicate structures of the cochleea for the future therapies [15, 16].

The outcome of implantation in congenital deafness is the best when the cochlear implantation is performed as early as possible, ideally in the first 18 month of life [17].

Clinical outcomes differentiate early and late implantations with regard to auditory performance. Very late implantation (in teen ages) in prelingually deaf does not lead to speech understanding and includes difficulties in more complex auditory tasks. Even after years of experience, performance is influenced by implantation age [18]. Early implanted children perform significantly better than later-implanted children. Late implanted subjects will not develop the ability to differentiate speech but they will still benefit from cochlear implant by the awareness of sound.

The fore-mentioned theories have been proved both in animals and in humans. Immediately after birth, the printing period begins. Hearing deprivation was experienced on birds and rare cases of human without speech exposure – for example, Aveyron boy case study (a child who was captured by hunters after surviving about 12-13 years in a wolf-family and although he had a normal hearing the lack of exposure to speech made him, mental and psychological, equivalent of someone born deaf) [19] suggest that early childhood exposure to speech results in better language development.

The psycho-social integration of the hearing-impaired child therefore necessitates the reintroduction of the individual into the sound environment. Despite an early intervention – before developmental period, the brain changes induced by complete absence of hearing from birth are difficult to totaly reverse despite years-long sensory experience following therapy of the defect [20]. To obtain a near to normal development of the congenital deaf child early intervention is mandatory. This is possible where coherent health policies exist: universal hearing loss screening, comprehensive genetic tests followed by genetic counseling whenever necessary, early diagnosis and treatment (conventional hearing aids or/and cochlear implants) – up to age of 9 months, speech therapy, follow-up of the child. An important factor that contributes negatively to the early cochlear implantation of children is parental refusal [21, 22].

 

5. Management of congenital profound deaf child

There are some general principles in management of congenital profound deaf child:

1.   The first principle is that of an early diagnosis. Ideally the congenital hearing loss has to be diagnosed at birth. During the first few months of life there are several factors to consider: narrow external auditory canal, behavior, cyrcadian rhythm, audiometric curve inaccuracy (after 6 months of age the association of behavioral audiometry with auditory evoked potentials allows a more accurate diagnosis).

2.   Using a battery of audiological tests. They can establish a precise diagnosis for each ear.

Clinical  evaluation,  evoked  auditory  potentials,  auditory  steady  state  response, behavioral audiometry are required [22].

3.   Early treatment - consisting in conventional hearing aids or/and cochlear implants.

4.   Hearing rehabilitation must be associated with speech ththerapy.

5.   Continuous monitoring of the child and his/her family by the cochlear implant team.

 

6. Conclusions

In conclusion it is important to emphazise the huge impact of early diagnosis and treatment (best before the first year of life) of congenitaly deaf child on his/her language development as well as on academic and social future life. A coherent health policy is mandatory to obtain this goal with an immense impact on the entire life of the children.

 

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Contribution selected by Filodiritto among those published in the Proceedings “National ENT, Head and Neck Surgery Conference - 2018”

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