• cochlear implant
• cross-modal
• deafness
• rehabilitation

Hearing loss (HL) is a pressing global health concern that bears significant individual and societal implications, reaching beyond audiological challenges to impact communication, mental well-being, and overall quality of life. Moreover, untreated HL carries a substantial economic burden, contributing to reduced productivity and increased healthcare expenditures.
For many hearing-impaired individuals, even with the aid of hearing aids (HAs) or cochlear implants (CIs), one of the most demanding tasks remains understanding speech in noisy environments, which is closely tied to spatial hearing and the perception of binaural cues.
Recent research has highlighted the significant advantages of integrating information from various sensory modalities, a phenomenon known as cross-modal stimulation. It has been demonstrated that visual cues can modulate the mental representation of sound sources and spatial hearing. This PhD thesis aims to investigate whether a training program based on cross-modal audio-visual stimulation can benefit the hearing-impaired population, particularly cochlear implant recipients.
A monocentric national prospective clinical intervention study was conducted to assess the effectiveness of a medical device designed for cross-modal audio-visual stimulation in unilateral cochlear implant recipients. Subjects were voluntarily recruited during routine visits to the cochlear implant clinic at the University Hospital of Pisa. A control group of typically hearing individuals was also included.
Both the study group and the control group underwent evaluations before the rehabilitation (T0) and at the conclusion of the treatment (T1). The following parameters were assessed in each evaluation:
1. Localization abilities
2. Speech perception abilities in silence and with background noise
3. Speech Reception Threshold (SRT) assessed using the Italian Matrix Test
4. Patients' reported outcomes (PROs) questionnaires
The rehabilitation protocol was based on prior experiences with hemianopsia patients and was adjusted for each subject based on their feedback.
In the study group, the mean error in localization dropped from 53.37° at T0 to 41.33° at T1. In the control group, the mean error in localization was 14.7° at T0, and 11.4° at T1.
Although the mean improvement in localization in the study group narrowly missed statistical significance (p = 0.068), the difference in localization abilities between the two groups was statistically significant.
The study group demonstrated a mean disyllabic words perception of 83.75% in silence at T0, which increased to 86.25% at T1, but no statistically significant differences were observed.
Speech perception abilities in silence and with background noise as well as SRT values in both groups showed no statistically significant differences before and after rehabilitation.
Further, PROs results for the study group remained largely consistent from T0 to T1, with no statistically significant differences.
This research provides valuable insights into the potential benefits of cross-modal audio-visual rehabilitation programs for cochlear implant recipients, though further investigations with larger and more diverse hearing-impaired cohorts are warranted.
Addressing the limitations of this study and conducting longer-term follow-up research would bolster the validity and reliability of these findings.