Treating tinnitus in single sided deafness with cochlear implantation is an exciting prospect for many frustrating patients with poor quality of life.
The causes of single single sided deafness
Single-sided deafness (SSD) is defined as a severe to profound hearing loss in one ear and normal to nearly normal hearing in the contralateral ear.
SSD affects an estimated 3 % to 6 % of the population. SSD and asymmetric hearing loss (AHL) can be caused by different diseases. Sudden sensorineural hearing loss (SSNHL) is the most common cause. Other causes include Meniere’s disease, unilateral vestibular schwannoma, temporal bone fractures, unilateral noise damage, and infections (labyrinthitis, mumps, meningitis).
Single sided deafness and tinnitus
Both SSD and AHL can lead to significant communication challenges due to decreased speech perception in noise and difficulty with localization of sound.
A large proportion of patients with acquired SSD and AHL experience tinnitus. A study by Chiossoine-Kerdel et al., (2000) documented tinnitus in 67 % of patients with SSNHL. A moderate to severe tinnitus handicap was recorded in 29 % of these patients.
Traditionally this condition was rehabilitated by adjustments of hearing systems with routing of acoustic signals from the healthy ear to the deaf ear, for example, with a bone anchored or osseointegrated auditory device (Ponto) or contralateral routing of the signal (CROS). The shadow effect can be improved by these devices but it usually has very little effect on the perception of tinnitus.
What is the cause of tinnitus?
Tinnitus is defined as a perception of sound (usually a tone/buzzing) without any external sound source. The pathophysiology of tinnitus is not yet fully understood. There are different theories and it is assumed that a peripheral lesion of the cochlear hair cells induces a suboptimal plasticity of the central nervous system. This induces reorganization and hyperactivity in the central auditory and nonauditory structures. Consequently, the perception of tinnitus might be affected by restoring hearing by cochlear implantation.
The effect of cochlear implantation on tinnitus
A recent systematic review of cochlear implantation in patients with bilateral hearing loss showed that most patients had a decrease in their perception of the tinnitus after cochlear implantation according to the Tinnitus Handicap Inventory (THI), tinnitus loudness, and annoyance. The THI by Newman et al.,(1996) is the most commonly used tinnitus questionnaire which is internationally validated.
This questionnaire is highly responsive to treatment-related change and is used as the gold standard in tinnitus evaluation.
In an attempt to treat severe to profound tinnitus in patients with post lingual SSD, a group of patients were fitted with cochlear implants by Van de Heyning et al., (2011).
A number of studies demonstrated that cochlear implantation represents an effective treatment option for tinnitus in patients with SSD. It was also demonstrated that a cochlear implant (CI) improved the understanding of speech in noise and the ability to localize sound.
Treating tinnitus with cochlear implantation
Unfortunately, so far, this rehabilitation technique for tinnitus in SSD is not funded by the health authorities in most countries.
Due to the nature of cochlear implantation in SSD, performance and selection bias exists because most of the included studies are not randomized controlled trials. This resulted in the fact that most of the included studies showed a high or moderate bias risk. The studies were nevertheless able to demonstrate in this review that the mean tinnitus questionnaire scores were decreased after cochlear implantation in all included studies. These results showed a clear improvement of tinnitus in SSD after cochlear implantation.
The effect of tinnitus suppression could be attributed to the effects of electrical stimulation. It is also assumed that the CI induces a restoration of central auditory pathways and an induction of neuroplasticity, which may then affect tinnitus perception.
It is important that patients with disturbing tinnitus are counselled with regards to the prognosis of tinnitus improvement after cochlear implantation, with nearly 90 % of patients reporting a suppression of their tinnitus. For more information contact any of the practices of CHi . Contact CHI