Five years audiological outcomes of the first Saudi Auditory Brainstem Implant (ABI)

Murad O Al-Momani

doi:10.4103/1319-8491.275311

CLINICAL CASE

Year : 2017 | Volume : 19 | Issue : 1 | Page : 32-34

Five years audiological outcomes of the first Saudi Auditory Brainstem Implant (ABI)

Murad O Al-Momani
Chairman of audiology and balance unit ENT department, college of medicine king saud university, Riyadh, Saudi Arabia

Date of Web Publication

7-Jan-2020

Correspondence Address:
Ph.D Murad O Al-Momani
P O. Box 245 Riyadh 11411
Saudi Arabia

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-8491.275311

Abstract

Absence of the cochlear nerve (cochlear nerve aplasia) or complete labyrinthine aplasia (Michel aplasia) is a rare inner ear congenital anomaly. Children born with cochlear nerve aplasia and/or Michel aplasia are deaf and cannot develop speech and language.
Conventional hearing aids and/or cochlear implant are of no benefit to manage this condition. The only available option to help children with this condition have a sense of hearing is by directly electrically stimulating cochlear nuclei in the brain stem through a device called auditory brain stem implant (ABI).
The main objective of this report was to present audiolgical outcomes over 5 years period for a child who received the first ever ABI in Saudi Arabia in 2011. The ABI procedure, programming and follow up were done at King Khalid University Hospital and King Abdulaziz University Hospital in Riyadh.
Results revealed good sound detection to both testing stimuli and environmental sounds. The child developed 2 word sentences which helped her communicate more effectively. These results are comparable to results of other ABI centers worldwide. In conclusion; audiological results of the first ABI in Saudi Arabia are positive and very well in agreement with results worldwide.

Keywords: Auditory Brainstem Implant (ABI), Cochlear nerve aplasia, Michel aplasia, cochlear implant

How to cite this article:
Al-Momani MO. Five years audiological outcomes of the first Saudi Auditory Brainstem Implant (ABI). Saudi J Otorhinolaryngol Head Neck Surg 2017;19:32-4

How to cite this URL:
Al-Momani MO. Five years audiological outcomes of the first Saudi Auditory Brainstem Implant (ABI). Saudi J Otorhinolaryngol Head Neck Surg [serial online] 2017 [cited 2023 Jan 30];19:32-4. Available from: https://www.sjohns.org/text.asp?2017/19/1/32/275311

Introduction

Cochlear implants (CI) have been long regarded to be the gold standard treatment option for bilateral severe to profound sensorineural hearing loss. This treatment option, however, requires the presence of normal cochlea and auditory nerve to have successful outcomes ^[1]. Cochlear implants can also be performed with some congenital cochlear malformation such as common cavity or Mondini dysplasia but the outcomes are usually less successful. Other congenital cochlear malformations such as absence of cochlear nervre (cochlear nerve aplasia) or complete labyrinthine aplasia (Michel aplasia), CI is not a possible option and is considered a contraindicated procedure ^[1].

Cochlear nerve aplasia or Michel aplasia are extremely rare congenital malformations and accounts for around 1% of all inner ear congenital malformations. Diagnosis of such conditions requires audiological assessment including auditory brainstem response (ABR) and otoacoustic emission (OAE) in addition to computed tomography (CT) scan and magnetic resonance imaging (MRI) ^[2].

Children born with cochlear nerve aplasia or Michel aplasia have profound sensorineural hearing loss. Children with no treatment develop no speech and mainly communicate by sign language ^[2],[3]. Lately, however, surgical implantation of an electrode on the cochlear nuclei in brainstem referred to as auditory brainstem implant (ABI) was used to manage above cases ^[4]. ABI involves placing electrode array on the dorsal and ventral cochlear nuclei [Figure 1]. Direct electrical stimulationform the speech processor of the device is delivered directly into the central auditory pathway ^[5].

Figure 1: display of the placement of the ABI electrode array on top of cochlear nuclei in the brainstem.

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Case Report

A 4 year old deaf and mute Saudi female child was referred to our clinic for hearing evaluation. Comprehensive audiological evaluation was performed including tympanometry 226 Hz, pure tone audiometry (PAT), OAE and ABR.

Results revealed bilateral normal tympanogram, no response to pure tone audiometry testing and absent OAE bilaterally. ABR using click stimulus and tone burst stimulus to 500 and 1000 Hz yielded no reproducible waves at maximum intensity level of 90 dBnHL. The child was then referred to the otology clinic for further investigation.

The otologist ordered CT scan and MRI of the temporal bone. Radiology report indicated absent cochlea and cochlear nerve bilaterally. The child was diagnosed with bilateral congenital cochlear aplasia with Michel aplasia.

Various management options were discussed in a multidisciplinary team consisting of an otologist, a neurosurgeons, audiologists and speech pathologists. Management options were narrowed down to either teach the child alternative communication methods such as sign language or to perform ABI. Results of testing as well as management options were discussed with the parents. Parents opted to have ABI performed for their child as they wanted their child actually to hear and possibly speak after the surgery. Extensive counseling was given to parents by the team to stress out realistic expectations of ABI outcomes. Parents were told that their child may have only speech detection, have no speech discrimination, hear environmental sounds only and may never develop normal speech and language. The father signed the consent form for the surgery after verbal understanding of the possible outcomes as described above.

ABI surgery was performed for the left ear at King Khalid University Hospital (KKUH) of King Saud University (KSU) in Riyadh in 2011. This was the first ever ABI in Saudi Arabia as well as the Arab world. Surgery went smoothly with no complications. Cochlear nucleus 24 device (21 electrodes) from cochlear corporation was used [Figure 2]. Electrical ABR (EABR) was used to verify a response form the cochlear nuclei to make sure that electrode array is placed correctly in place [Figure 3]. Other cranial nerves such as, V, VII, IX, X, and XI were monitored by neurophysiologist to make sure no unwanted stimulation occur during EABR testing. EABR showed repeatable wave V at all electrodes with no unwanted stimulation of other cranial nerves.

Figure 2: Nucleus 24 ABI system. External speech processor (A), receiver-stimulator (B) and electrode array (C).

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Figure 3: Electrical ABR (EABR) tracings. Wave V is shown with good repeatability at one of electrodes.

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Six weeks later, first switch-on of the device was done at King Abdualziz University Hospital (KAUH) under general anesthesia with heart and oxygen monitoring for child’s safety. This step was done as an extra precaution in case the electrode array moved after the surgery, which may stimulate vital cranial nerves such as X cranial nerve and create cardiac arrhythmias. First switch on of the device produced robust EABR at all electrodes with no unwanted side effects indicating thatelectrode array did not move after surgery.

In the audiology clinic, programming of the device was then done in the second day while the child was alert. The child detected the sound when was stimulated at all electrodes. Follow up programming sessions was done on regular basis to establish an optimum program in terms of threshold level (T level) and comfort level (C level). Final program was reached within 3 months after first switch-on. The child underwent regular speech therapy program for the following 4 years.

Results

During the first two years after the implant, the child aided PTA was at around 30 dBHL for frequencies 250-8000 Hz. The child had good sound detection, good hearing of environmental sounds, and 30% word recognition with visual cues but very poor (10%) word recognition without visual cues. Additionally, speech production was very poor and was limited to few single word sentences. In the following 3 years, word recognition without visual cues improved to around 30% and with visual cues to around 70%. Speech production improved slightly, the child now produces few two word sentences to communicate with others. The child’s ability 14p0-y to communicate has improved although this is done in conjunction with lip reading and sign language.

Discussion and Conclusion

ABI outcomes are well documented to be significantly poorer than CI worldwide ^[6],[7],[8]. Most patients’ ABI performance is equivalent to single channel CI performance. Only few (around 10%) ABI patient’s performance is equivalent to 2-3 channel CI performance. The exact reason for worse ABI speech recognition performance as compared to that of CI is not fully understood. However, lack of consistent pitch mapping was proposed as a major problem in ABI as compared to CI. Frequency tuning in cochlear nuclei is oriented orthogonal to surface, while electrode array in ABI lies parallel to the surface ^[9].

Although performance with ABI is worse than with CI, ABI improves ability to communicate and be in touch with others over lip reading alone. Moreover, ABI aidspsychological status and physical safety of childrenand help them be better connected to the environment and people around ^[10].

Results of our first ABI implant at our center are comparable to results of other centers worldwide. We consider this as a successful step forward in management of hearing loss using ABI. We believe that, ABI helped the child live a better quality of life as was also verbalized by the parents.

References

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