Predictive Factors of Hearing Rehabilitation After Cochlear Implant Surgery in Deaf Patients

Cochlear implants are indicated in France in cases of severe to profound bilateral sensorineural hearing loss with an audiometric threshold of less than or equal to 50% speech discrimination in silence in the Fournier list (or equivalent) at 60 dB, in the free field, with well-fitted hearing aids. Cochlear implant represents a major advance in the management of severe to profoundly deaf patients and has also shown a benefit in the prevention of neurodegenerative diseases.

An average of 1800 cochlear implants are placed in France per year, 58% of which are placed in patients over 18 years of age.

The results of cochlear implants are in favour of a benefit in speech comprehension compared to hearing aids in cases of severe to profound deafness. However, there is a strong disparity in hearing performance after cochlear implantation from one patient to another, whether in silence or in noise.

Several factors influencing the results of the implant have been identified. Some of them are linked to the patient: etiology of the deafness, duration of auditory deprivation, age at implantation, residual hearing, pre- or post-lingual status of the deafness, some others are related to implant surgery (insertion of the electrode in the tympanic ramp, complete insertion, presence of a translocation, depth of electrode insertion).

Finally, there are factors related to the quality of the settings of the implant and to the brain plasticity of the patients.The 4 main factors seem to be the duration of the deafness, the age of onset of the deafness, its etiology and the duration of the patient's experience with the implant. It is assumed that the performance of cochlear implantation is strongly related to the individual's auditory processing abilities and the integrity of the central nervous system from the auditory nerve to the cortex.