Genotype-phenotype Correlation Study of Presymptomatic and Symptomatic DFNA9 Patients

Evaluation of Hearing and Vestibular Function in Presymptomatic and Symptomatic DFNA9 Patients Carrying the Pro51Ser (P51S) Mutation in the COCH Gene.

DFNA9 (Deafness Autosomal Dominant 9) is an autosomal dominant hereditary hearing loss which is associated with vestibular deterioration. The most recent genotype-phenotype correlation studies have been conducted more than 15 years ago. Meanwhile, emerging and valuable vestibular tests have been added to the vestibular test battery. These tests were not available at the time of the correlation studies. The aim of this study is to carry out a prospective cross-sectional study on symptomatic and presymptomatic affected carriers of the Pro51Ser (P51S) Coagulation Factor C Homology (COCH) mutation in order to correlate vestibular data using the complete vestibular test battery with the known data on hearing and vestibular function in relation to age.

Systematic review of the genotype-phenotype correlation studies in P51S carriers has shown an underrepresentation of presymptomatic affected subjects and the calculation of vestibular deterioration were based on just one vestibular parameter, whereas the combined evaluation of a complete vestibular test battery, covering the complete vestibular sensitivity range and all labyrinthine compartments separately, is nowadays considered standard practice in determining more accurate assessment of the vestibular function.

For this reason, a prospective cross-sectional study on pre- as well as symptomatic DFNA9 patients carrying the Pro51Ser (P51S) mutation in COCH gene is being carried out, in order to gain more realistic data on vestibular dysfunction, consisting of pure tone audiometry and a comprehensive vestibular test battery, including electro- or videonystagmography (VNG), C- and O-Vestibular-evoked myogenic potential (VEMP) tests, video Head Impulse Test (vHIT) and questionnaires (DHI (Dizziness handicap Index), oscillopsia questionnaire (OS), Quality of Life Questionnaire (EQ-5D-5L), activities-specific balance confidence (ABC) scale.

Inclusion Criteria:

• subject must be 18 year of older
• subject is a family member of the family pedigree's proband(s) carrying a P51S COCH mutation

Exclusion Criteria:

• subject is younger than 18 years
• subject is not a family member of the pedigree's proband(s) carrying a P51S
• subject cannot undergo investigations (medical and/or mental reasons)
• subject is not willing to be enrolled into the study
• subject suffers other concomitant middle or inner ear disease
• subject has undergone middle ear or inner ear surgery
• subject suffers other concomitant vestibular disease than DFNA9
• subject has undergone vestibular surgery or other non-invasive vestibular treatment (gentamicin intratympanal injections for example)