Tinnitus modifications after cochlear implantation.

Tinnitus can be defined as a phantom sensation in the absence of an external sound. In our study, we evaluated the effect of cochlear implant on tinnitus evolution. Among adult, postlingually deaf patients who underwent cochlear implantation at our clinic, we selected 20 subjects with pre-implantation tinnitus (group A) and 10 subjects without pre-implantation tinnitus (group B). Pre- and post-surgery tinnitus was assessed through two questionnaires: the first one dealing with tinnitus characteristics and psychosocial impact, and the second one represented by THI, an internationally validated score of evaluation of the effects of tinnitus on patient's emotions and activities of daily living. None of the patients belonging to group B developed tinnitus after surgery. As for group A, 40% of patients declared suppression of tinnitus, 30% attenuation of tinnitus after surgery, 25% reported tinnitus was unchanged and 5% reported worsening of tinnitus. In the nine patients with bilateral tinnitus (45%), after implantation tinnitus disappeared from both sides in four patients and attenuated bilaterally in four patients. A comparison between pre- and post-implantation THI scores showed decreased score in 65% of cases, unchanged score in 30% and increased score in 5%. The beneficial effect of cochlear implant on tinnitus, reported by a majority of patients, could be due to acoustic masking, to direct electrical stimulation of the acoustic nerve, and above all to a possible cochlear implantation dependent reorganization of the central auditory pathways and associative cerebral areas. In the light of these results, the authors propose (1) to include tinnitus in the selection criteria of which ear to implant; (2) to consider implantation eligibility for patients with bilateral severe hearing loss associated with severe tinnitus; and (3) to inform patients about the small risk of post-operative tinnitus worsening.