Phd in CLINICAL EXPERIMENTAL NEUROSCIENCE AND PSYCHIATRY

Thesis title: Tinnitus and Tolerance to Loudness in Adult Cochlear Implant Users: Audiological, Psychological, and Speech Perception Correlates

Objective: This study explored the interplay between tinnitus, hyperacusis, psychological factors (anxiety and depression), and auditory performance in adult cochlear implant (CI) users. The aim was to identify predictors of post-implantation tinnitus outcomes and their implications for rehabilitation. Methods: A nested case-control study was conducted on 50 adult CI users (63 ears), divided into a tinnitus group with persistent symptoms post-implantation (study group, SG), and two control groups: control group 1 (CG1; tinnitus resolved after implantation) and control group 2 (CG2; no history of tinnitus). Audiological variables included sound field pure-tone average (SF-PTA) and speech perception in quiet and in noise (Italian Matrix Sentence Test, It-Matrix). Measures for tinnitus distress and subjective symptoms to sound loudness included the Tinnitus Handicap Inventory (THI), Khalfa Hyperacusis Questionnaire (KQ), while psychological factors explored were the state and trait anxiety (STAI-Y 1-2), and depressive symptoms (Beck Depression Inventory-II (BDI-II). Cluster analysis was conducted to identify subgroups with distinct clinical profiles. Results: In the SG, 35.3% of patients showed improvement in THI grade, 47.1% remained stable, and 17.6% worsened. Hyperacusis affected 64.7% of SG and was significantly associated with higher STAI-Y and BDI-II scores and poorer It-Matrix performance. SF-PTA thresholds in the CI ear, including the better-performing ear in bilaterally implanted patients, were negatively correlated with tinnitus severity, loudness, and annoyance, as well as with psychological distress, as measured by STAI-Y and BDI-II scores. It-Matrix was positively associated with both psychological distress and severity of loudness intolerance to electrical stimulation. Cluster analysis created three subgroups with differing profiles: one with worse-than-average SF-PTA thresholds and marked hyperacusis, but with mild tinnitus distress and minimal psychological symptoms; one with favourable auditory (low tinnitus and hyperacusis, optimal SF-PTA thresholds) and psychological outcomes; and one with poor auditory performance, moderate tinnitus handicap, significant hyperacusis, and elevated emotional distress. Conclusions: Persistent tinnitus and hyperacusis remain significant clinical challenges in a subset of CI users, particularly in cases characterized by auditory asymmetry and psychological comorbidities. Poor speech perception in noise may further exacerbate emotional distress. Cluster analysis highlights the heterogeneity of the CI population and supports the importance of a personalized, multidisciplinary rehabilitation approach, especially for individuals with complex symptom profiles requiring integrated psychological and audiological care. These findings reinforce the need for individualized rehabilitation strategies, including psychological screening and tailored CI programming, to improve long-term outcomes and overall quality of life.