INFLUENCE OF THE CAUSES OF HEARING LOSS ON SPEECH PERFORMANCE AFTER COCHLEAR IMPLANTATION IN GREEK CHILDREN WITH PRELINGUAL HEARING DISORDERS

INFLUENCE OF THE CAUSES OF HEARING LOSS ON SPEECH PERFORMANCE AFTER COCHLEAR IMPLANTATION IN GREEK CHILDREN WITH PRELINGUAL HEARING DISORDERS

Konstantina Napoleaon Lili

PhD student, South-West University “Neofit Rilski”,

Blagoevgrad, Bulgaria

Katya Dionissieva

Assoc. Prof. PhD, South-West University “Neofit Rilski”,

Blagoevgrad, Bulgaria

ABSTRACT

Background: Cochlear implants (CI) - high technologicat devices are nowdays a popular options for stimulating residual hearing of children with severe hearing disorders. In this paper are examined some differences in speech performance according to cause of hearing loss based on a research that  was conducted in Greece.

Method: We conducted a study of the documented cause history of students' hearing impairment and their auditory performance. In parallel, an evaluation and report of levels of speech word performance of the targeted group was done.

Results: High levels of auditory performance were measured for hearing loss due to Cytomegalovirus infection followed by those with Auditory Neuropathy Spectrum Disorder while for hearing loss due to family history lower levels of auditory performance were registered. The score of monosyllabic words was higher after Cytomegalovirus infection followed by Auditory Neuropathy Spectrum Disorder while lower levels of auditory performance were presented in hearing loss due to Large Vestibular Aqueducts.

Conclusions: Levels of both auditory and speech performance are different due to specific causes of the hearing disorder. When the reason of the hearing loss is known the perspectives for mastering of audition and development of language in prelingualy deaf children may be better planned and will support their communicative and academic achievements.

Keywords: Cochlear implant, Cause of hearing loss, Speech performance

Introduction

The application of cochlear implants is an established method of restoring a severe hearing loss. The multichannel cochlear implant has become a widely accepted prosthetic device for deaf children and adults. As a result, many deaf people have managed to gain some degree of sound intake by having cochlear implants. Benefits have also been observed in children, including those who had lost their hearing before developing the ability to speak. Additionally, it is certain that the benefits obtained are improved by the continuous use [5].

There are many reasons that are responsible for hearing loss and there are also different degrees of speech performance of children that are implanted with cochlear Implants that has to do with the cause of hearing loss.

Causes of hearing loss

The reasons that can cause a hearing loss or deafness are too many and they are generally divided into two categories, relative hearing problems and those problems that appear after an incident.

Relative hearing problems are those caused by genetic causes reported before the child's birth and divided into three subcategories [7].

1. Genetic. They are transferred with specific chromosome genes from the parents.
2. Embryopathy. Various maternal conditions such as diabetes, nephritis, toxoplasmosis, poliomyelitis, syphilis and especially viral infections, the most prevalent of which are red in the first three months of pregnancy. It may also be due to the radiation effect or to medications that the expectant mother took.
3. Perinatal (acoustic loss during delivery). Injuries, i.e., head injuries during labor may cause bleeding in the fetal skull and premature labor may cause alterations in the sound perception system as well as nuclear jaundice.

Accepted hearing loss is the cause of the child's birth. These causes are due to various diseases such as mumps, meningitis, (epidemic and tuberculous), encephalitis, pertussis etc. Drugs (streptomycin, biomomycins, diuretics, etc.) and traumatic lesions (excessive noise, surgical errors, etc.) are also listed. Further come middle ear inflammations (secretory otitis media, acute otitis media, ear otitis media, etc.). In pre-lingual deaf people acoustic loss is usually great, so they cannot hear the human voice. Their oral speech and language will not grow spontaneously. They need special training to develop them [3]. For some children language learning is never achieved. Loss of hearing after word and language are developed is called metalanguage deafness. It does not prevent the child from making good progress at school [7].

Hearing diagnosis

The main diagnostic methods for hearing loss are examination by tinsters and audiological tests such as audiometry, echo sound, acoustic evoked potentials and electrooculography [1]. Actually, not in all cases of diagnostics the cause for poor hearing may be identified. Still researchers are interested in the effect of the causes of hearing disorders on treatment options and rehabilitation outcomes in pre-lingualy deaf children especially.

Stages of preoperative assessment for cochlear implantation

Cochlear implants are now a reality in Greece and in the near future, they will constitute a routine for dealing with deafness of cochlear etiology. The therapeutic success of this technological innovation must be attributed to the fact that an artificial instrument replaces the hearing organ with an electronic system [4]. To ensure the proper functioning and effectiveness of this system, careful preoperative assessment is required.

The evaluation begins with a history of deafness, otorhinolaryngology and anaerobic examination for the detection of bilateral cochlear imbalance. It continues with a check on the general health and psychological-psychiatric profile of the candidate. Electroacoustic control, i.e. electrical stimulation of cochlear nerve, followed by CT and magnetic resonance imaging (MRI) is performed to illustrate the temporal bone structures, in particular the screw threads, as well as the brain. Finally, the particularities of each case are recorded, which can significantly affect the implantation process [4].

The role of age: Young children usually do not cooperate during preoperative testing, both in the deafness test and in the CT or CT scan. It is not easy, at very younger ages, to determine the dynamic zone of the cochlear nerve during the Cape Test. In such cases anesthesiologist may be needed to help [4].

The etiology and duration of deafness: It needs to be clarified if it is deafness of pure cochlear etiology, since, in retrograde damages, the cochlear implant does not work. In such cases, the possibility of placing the electrode in the cochlear nuclei in the brain stem is examined. Pre-lingual patients, other than children less than 3 years of age, who develop brain plasticity capabilities, do not have the prognosis of post-lingual candidates whose progress in cochlear implantation is better due to existing auditory memory. People with recent deafness have a better prognosis than those whose deafness dates back to the past [6].

The ability of communication: Candidates who have developed other ways of communicating, and especially the ability to read, as well as those who have lost their hearing progressively but have used hearing aids, have made better progress in speech therapy following cochlear implantation [6].

Practical research and results

Taking into consideration the findings discussed above and in accordance with the objectives of a broader research, we investigated how language development of Greek children, users of cochlear implants, is influenced by the cause of hearing loss. The following research question was formulated:  Is there a statistically significant relationship with the cause of hearing loss of children with CI and their further speech development?

Primary schoolteachers of 114 hearing-impaired children with CI at different Greek mainstream schools were invited to participate in the research. They conducted a study of the documented cause history of their students' hearing impairment and auditory performance. In parallel, the teachers were asked to evaluate and report  the levels of speech word performance of the targeted group. The indicators for this assessment were based on the following diagnostic tools: Speech perception (Auditory performance & Monosyllabic words) by reason of hearing loss. The analysis of the data was done with the statistical software SPSS version 24. Descriptive statistics were applied to illustrate the related results of the target group.

Results and analyses

• Cause of hearing loss

Figure 1 presents the results regarding the reason of hearing loss. Specifically, the majority of students lost their hearing as a consequence of gene mutation (36.8%) following by family history (21.9%) and large vestibular aqueducts (17.5%).

Figure 1. Causes of hearing loss

• Category of auditory performance

Figure 2 presents the results regarding the category of auditory performance. Specifically, the majority of students recognize environmental sounds (26.3%) following by responds to speech sounds (22.8%) and discrimination of at least two speech sounds (19.3%). On the contrary, only 3.5% understand conversation with a familiar talker without lip-reading.

Figure 2. Category of auditory performance

• Word performance

Regarding word performance, the score on phonemes was 71.8% while on monosyllabic words 59.7% (Figure 3).

Figure 3. Word performance

• Speech perception (Auditory performance & Monosyllabic words) by cause of hearing loss

The following table show the means of indicated speech perception by reason of hearing loss. Specifically, the levels of auditory performance are higher for those who lost their hearing ability due to Cytomegalovirus infection (M = 4.00, SD = 1.15) followed by those with Auditory Neuropathy Spectrum Disorder (M = 3.17, SD = 1.87). On the contrary, lower levels of auditory performance are presented for those who lost their hearing due to family history (M = 1.96, SD = .978).

Additionally, the score in monosyllabic words perception is higher for those who lost their hearing ability due to Cytomegalovirus infection (M = 91.10, SD = 4.40) followed by those with Auditory Neuropathy Spectrum Disorder (M = 85.05, SD = 10.32). On the contrary, lower scores of monosyllabic words perception are presented for those who lost their hearing due to Large Vestibular Aqueducts (M = 45.15, SD = 25.93).

Table 1.

Auditory performance and speech perception by cause of hearing loss

Conclusions

Levels of language development are higher when for those who lost their hearing ability due to Auditory Neuropathy Spectrum Disorder followed by those with family history. However, the reason of hearing loss is a not determinant factor of language development levels. Additionally, the score of monosyllabic word perception is higher for those who lost their hearing ability due to Cytomegalovirus infection followed by those with Auditory Neuropathy Spectrum Disorder. Lower levels of auditory performance are presented for those who lost their hearing due to Large Vestibular Aqueducts.  

Levels of both auditory performance and speech perception are different due to specific causes of the hearing disorder. When the reason of the hearing loss is identified early the perspectives for mastering of audition and development of language in prelingual deaf children by the means of cochlear implantation could be better determined and thus support their communicative skills development and academic achievements.

The tremendous development in the field of medicine and technology provides us with two breakthrough achievements, digital hearing aids and cochlear implants that are constantly evolving and improving, and have radically changed the education of hearing impaired children. For sure they are opening up new integration options for them into formal education and providing opportunities to attend and participate in the educational process without their hearing impairment being an obstacle.

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