People with unilateral hearing loss now have the opportunity to hear out of both ears. In July, the FDA approved the use of cochlear implants for single-sided deafness and asymmetric hearing loss for patients 5 years of age and older based on data from a clinical trial conducted by Margaret Dillon, AuD, and the UNC Cochlear Implant Clinical Research lab.
About Single Sided Deafness (SSD) & Asymmetric Hearing Loss (AHL)
SSD and AHL affects people in all stages of life and can have a significant impact on a person’s quality of life. It can be caused by viral infections, Meniere’s disease, or trauma to the head or ear. In some cases, the causes are unknown.
Recent data estimates that 7.2% of Americans report some degree of hearing loss on one side, with 5.7% having mild and 1.5% reporting moderate-or-worse hearing loss on one side, translating to an estimated 4.9 million American Adults. Until now, treatment options were limited to hearing aids and CROS systems that provide limited or no benefit for people with profound hearing loss in one ear.
People with SSD and AHL experience difficulties hearing in certain situations such as noisy environments, and these difficulties have a negative impact on communication and social interaction. It can also negatively affect speech and language development in children and work performance among adults. These difficulties can be attributed to the lack of binaural summation, the head shadowing sounds on the opposite side of the hearing ear and the inability to localize sounds.
Previously available options in the US such as CROS hearing aids and bone conduction devices do not restore binaural hearing as they only reroute the signal to the hearing ear. These therapeutic options restore neither sound localization nor spatial hearing, which means patients still face significant difficulties with communication in daily life.
“Patients with single-sided deafness and asymmetric hearing loss experience difficulty with speech understanding in noise and localizing sounds in their environment,” said Margaret Dillon, AuD, Associate Professor, Director of Cochlear Implant Clinical Research, and Principal Investigator on the clinical trial. “Our data demonstrated early, significant benefits with cochlear implant use on measures of speech understanding in noise, localization, and subjective benefit.”
Clinical Trial Data
The approval was based on clinical data from a study at the University of North Carolina at Chapel Hill with 40 participants ages 18 and older to evaluate speech perception in quiet and noise, sound localization and quality of life. Trial participants had single-sided sensorineural profound hearing loss in one ear, or asymmetric hearing loss, for less than 10 years and had used a hearing aid regularly for at least some of that time. All of the people in the study had also tried some type of current hearing device to treat SSD, such as a hearing aid, bone-conduction device, or a CROS hearing aid. Subjects were implanted at the University of North Carolina at Chapel Hill with the Cochlear Implant System in this prospective, non-randomized, non-blinded, repeated measures clinical study.
Speech Understanding in Quiet
Both groups of people (SSD and AHL) improved their ability to understand speech in quiet after one year of implant use when tested with the implant alone. For the people with SSD, average scores when repeating single words in quiet increased from 4% before surgery to 55% after 12 months of listening with the implant. For the group of people with AHL, this same test score improved from 6% to 56% in 12 months. In the opposite ear, there was no change in their score over time. When tested with both ears, there was no change compared to the score before surgery.
Speech Understanding in Noise
When listening to speech in noise, both SSD and AHL groups improved over the first 12 months of listening with the cochlear implant compared to their unaided scores before surgery. The average improvement in the SSD group increased from 38% to 47% in 12 months on the AZ Bio Test, speech and noise from the front. This group also had an average increase from 17% to 53% on the AZ Bio Test when speech came from the front and the noise was on the side of the normal hearing ear. The AHL group saw increases from 23% to 34% when speech and noise came from the front, and 6% to 29% when speech came from the front and noise was on the side of the better hearing ear, also on the AZ Bio Test.
Finding the Direction of a Sound Source
People in both the SSD and AHL groups significantly improved in finding the direction of a sound after they had listened with the cochlear implant for 12 months. To take this test, listeners sat in a room with 11 speakers arranged in a half-circle in front of them, and they were asked to point to the speaker each sound came from.
Listeners were asked to complete two questionnaires about their experiences using the cochlear implant. After one year of listening, both groups (SSD and AHL) reported an improvement overall when asked about their impressions of the quality of speech, ability to locate sounds around them, and overall sound quality (SSQ Test) as well as ease of communication, hearing in background noise, and hearing in environments with an echo (APHAB Test)
One participant in the clinical trial, Mitch, lost his hearing suddenly in one ear following a traumatic accident at the age of 21. Mitch was faced with not only recovering from skull fractures and cranial bleeding but also resultant single-sided deafness, vertigo, and tinnitus. He did not experience benefit with the approved treatment options for single-sided deafness at that time.
Mitch pursued an evaluation with the UNC Cochlear Implant Clinical Research team in 2015, enrolled in the clinical trial, and underwent cochlear implantation. After only one month of cochlear implant use, Mitch demonstrated significant improvements in speech understanding in noise and localization of sound. He also reported significant improvements in his quality of life. Today, Mitch wears his cochlear implant daily and continues to have notable benefit with the device.
After demonstrating the significant benefit of cochlear implant use in adult subjects, the UNC Cochlear Implant Clinical Research Lab initiated a clinical trial on cochlear implantation in cases of single-sided deafness in children.
Sam, a pediatric subject, suffered from single-sided deafness at a very young age. He was typically outgoing and social, until he began to struggle at the age of four due to his resultant hearing loss from an infection following surgery. Sam could not localize sounds or function in loud environments because the different sounds became too much for him to process with only one normal-hearing ear. He transformed into a shy preschooler and isolated himself. After the family’s local physicians said nothing could be done for Sam medically at their center, Sam’s hearing intervention teacher referred the family to the Children’s Cochlear Implant Center at UNC.
In 2017, Sam underwent cochlear implantation by Kevin Brown, MD, PhD, Associate Professor, Chief of Otology/Neurotology, Skull Base Surgery, and Medical Director of the Children’s Cochlear Implant Center at UNC, and Principal Investigator on the pediatric clinical trial. Sam’s surgery was a success and he has returned to his outgoing self; he utilizes his cochlear implant daily and at the age of seven, has experienced notable improvements in his hearing and quality of life.