Cochlear Implantation: Expanding candidacy and Cost Effectiveness

Sheelu Srinivas

Consultant ENT Surgeon, Kauvery Hospital, Electronic City, Bengaluru, India

*Correspondence: drsheelusrinivas@gmail.com

Background

Cochlear implants are the most successful sensory prostheses worldwide. A cochlear implant (CI) is a surgically implanted device for the treatment of severe to profound sensorineural hearing loss (SNHL) in children and adults. It works by transducing acoustic energy into an electrical signal, which is used to stimulate surviving spiral ganglion cells of the auditory nerve.

The past 2 decades have witnessed an exponential rise in the number of CI surgeries performed. Continual developments in programming strategies, device design, and minimally traumatic surgical technique have demonstrated the safety and efficacy of CI surgery.

The indications for cochlear implantation have gradually expanded as advancements in technology have evolved, resulting in improved audiologic outcomes for both adult and children.

Indications for pediatric cochlear implantation have evolved from children with bilateral severe to profound SNHL to implanting children below 12 months, including those with residual hearing, asymmetric hearing loss, inner ear malformations, as well as cochlear nerve deficiency.

Adult cochlear implantation candidacy has progressed from patients with bilateral profound SNHL to include patients with greater degrees of residual hearing, single-sided deafness and asymmetric hearing, and atypical etiologies of hearing loss (e.g., vestibular Schwannoma, Ménií¨re’s disease disease, and otosclerosis).

Herein, we present two cases performed at our centre recently who have benefitted from this expanding candidacy guidelines and share the learning of our program over the last decade.

Case 1

A 42-year-old female presented with bilateral profound sensorineural hearing loss due to childhood chronic suppurative otitis media (CSOM). She had undergone right mastoid surgery a decade ago and her right ear was dry. Due to profound hearing loss in both ears and no benefit with hearing aids, she had become depressed and even contemplated suicide. She was worked up for candidacy and explained about post implantation auditory training.

Fig. 1. Receiver stimulator in situ.

Fig. 2. On table-C- arm Xray confirmation of electrode in cochlea.

We performed audiometric assessments include speech audiometry and confirmed her poor benefit with hearing aids. Radiological work up to confirm patent cochlea and auditory nerve was done. Thorough counselling was done about post implantation auditory training and realistic expectation from the device.

Case 2

13-year -old boy presented with gradually progressing sensorineural deafness from birth. He was given hearing aids at 2 years of age and underwent extensive auditory verbal therapy. However, over the recent year’s parents noticed changes in speech pronunciation and nasal quality – suggestive of deaf speech. We performed speech audiometry and aided audiometry and found him failing in open set speech and hearing benefit with aids. The child had sound awareness with hearing aids on left ear and it was decided to implant right ear. Radiology scans were done, and candidacy confirmed. He was advised cochlear implantation and underwent surgery last month. After 2 weeks of surgery, switch on was done and now child is undergoing auditory verbal therapy at our centre.

Binaural Hearing: our cochlear implantee with right cochlear implant along with left link hearing aids- this maximises his hearing benefit with both ears.

Discussion

The observation that electrical stimulation of the auditory pathway can create the perception of sound was discovered in 1790 by Alessandro Volta. In 1966, Simmons was the first to demonstrate the tonotopic organization of the cochlea, whereby different regions along the basilar membrane vibrate at different sinusoidal frequencies. One of the most significant advancements came with Dr.William House in the 1960s, who along with engineer Jack Urban, created the first implantable device that could stimulate the auditory nerve, making cochlear implants a clinical reality.

The original device was commercially marketed as the House/3M cochlear implant that utilized a single electrode array. During the late 1970s, Graeme Clark in Australia developed the first multichannel cochlear implant (Cochlear Nucleus Freedom), which had enhanced spectral perception and speech recognition capabilities compared with the single channel device. In the 1985, the Food and Drug Administration (FDA) approved the first multichannel CI for use.

Dr Sheelu Srinivas with Holly- World’s first commercial recipient of Pediatric cochlear implant done by Prof. Graeme Clarke.

Over the last 3 decades, advancements in surgical technique, electrode design, and improved speech processing strategies have led to increasingly better outcomes in CI recipients. As a result, FDA candidacy criteria have gradually expanded from initially only implanting post lingual deafened adults with profound bilateral SNHL to now implanting adults and children with greater degrees of residual hearing. Furthermore, a growing proportion of patients are undergoing CI for off-label or non-traditional indications including single sided deafness, retro cochlear hearing loss, such as with vestibular Schwannoma, asymmetrical SNHL in adults and children with at least one ear that is better than performance cut-off for age, and children less than 12 months of age.

The basic evaluation of CI candidates involves a medical, audiometric, and radiographic evaluation.

When we started our program 2009, our candidates were traditional recipients -prelingual deaf babies -children below 5 years. Most the children in our program have one sided ci. We performed our first bilateral ci in a 2-year-old in 2015.

In 2017, we started our work on expanded criteria and performed our first adult ci in a 63-year-old who had lost hearing due to CSOM. Later we implanted post lingual deaf adults with who lost hearing due to trauma, drug induced and viral illness.

The criteria of implantation are increasing and so are the beneficiaries. Post lingual adults are advised strict auditory training post implantation. Children who present with progressive hearing loss and plateaued benefit with hearing aids need auditory verbal therapy.

Cochlear implantation has demonstrated one of the highest cost-effectiveness ratings of common medical interventions, particularly in children. The development of oral language and enrolment in mainstream schooling are common metrics for determining the effectiveness of cochlear implantation in children. Similarly, in adults, the deafness disability is overcome, and they continue to be contributing members of their family and society.

In our country, the state sponsored cochlear implant programs have been running successfully in few states, many other deserving candidates struggle to get implants at the right time. Also, the need of processor upgrades adds to the economic burden of the financially weak.

A thorough pre-implant counselling of the candidates and families along with discussion of the ongoing maintenance prepares them for using the technology to its maximum benefit. State sponsored schemes should include the expanding criteria for candidacy as well as cover the ongoing maintenance costs of upgrades.

Dedication

Dedicated to adults and children with no usable hearing in one ear and some in the other, the combination of a Marvel Cl and a compatible Phonak hearing aid can help you or your child enjoy a more powerful connection to the world.