Functional Near Infra-Red Spectroscopic Study of Central Auditory System Cortical Functional Reorganization

Binaural hearing allows strengthening of speech intelligibility in noise and sound localization. It is well known that single-sided (SSD) and bilateral asymmetric deafness lead to socio-behavioral consequences and, in children, inducing impairments in learning acquisitions.

In adults, SSD is associated with a reduction of inter-hemispheric functional asymmetry of auditory cortex on functional Magnetic Resonance Imaging. Moreover, in children with bilateral profound deafness who got one cochlear implant (inducing a form of asymmetric hearing), these clinical and functional anomalies cannot be overcome in case of a late (>1,5year) secondary implantation. This shows that once the loss of asymmetry is installed, it is difficult to recover from it.

No data about SSD in children and its cortical representation exists. In this study, the investigators hypothesized that SSD modifies the auditory cortical activation profile, linked with a deterioration of the binaural auditory skills, the global development and the quality of life If this hypothesis is confirmed, systematic and individualized rehabilitation will be needed to reduce patient's handicap and to prevent long term consequences.

The investigators will then measure the auditory cortical activity using fNIRS in 5 to 16 year-old SSD and NH children. The fNIRS system will use a sensor-bearing cap, measuring cortical activity through the scalp. Binaural hearing (speech in noise and localisation), speech assessments (global and speech development), and QoL will also be measured.

Children will undergo 2 sessions of 1 to 2 hours tests, each spaced up to 3 months apart. As they are children regularly seen in our ear-nose-throat department, a once-a-year follow-up will be proposed, on the child and his family convenience. As it is a non-interventional study, no follow-up would be needed.

Inclusion criteria

For both groups:

• 5 to 16 year-old children,
• Absence of pregnancy
• Affiliation to Social Security, and children and their parents signed consents will be necessary.
• Participation agreement of the protocol and signature of the consent form by the person having parental authority and the child

For Single-sided Deafness subjects:

• shall present with moderate to profound unilateral hearing loss, with a hearing loss of 40 decibel(minimal thresholds), assessed on tonal, vocal audiometry, Auditory Brainstem Responses,

For Normal hearing subjects:

• shall have normal hearing, demonstrated by air thresholds below 20 decibel by an audiometric control before inclusion , matched in gender and age to children in the experimental group

Exclusion criteria

For both groups:

• Antecedents of Psycho-neurological diseases,
• Other sensorineural or motor deficiency,
• Familial bilingualism,
• Medications affecting vigilance.
• pregnancy or breastfeeding