Inherited nonsyndromic hearing loss. An audiovestibular study in a large family with autosomal dominant progressive hearing loss related to DFNA2.

OBJECTIVE To study nonsyndromic progressive sensorineural hearing loss (SNHL) with significant linkage to the DFNA2 locus on chromosome 1p in a Dutch kindred. DESIGN A 6-generation family with 194 family members was studied. Of the presumably affected persons, 43 were examined in detail to obtain audiograms and 37 underwent vestibulo-ocular examination. RESULTS Regression analysis showed significant and equal linear progression in SNHL with age (by about 1 dB per year) at all frequencies. Offset values were close to zero at the low frequencies (0.25, 0.5, and 1 kHz) but increased systematically with the frequency. It is likely that they represent congenital high-frequency SNHL: about 15 dB at 2 kHz, 30 dB at 4 kHz, and 50 dB at 8 kHz. Bilateral caloric weakness was not observed. A significant finding was that 25% to 35% (depending on the exclusion criteria) of the patients showed an increased vestibulo-ocular reflex (hyperreactivity) as measured by rotatory responses. Forty-one patients showed significant linkage to the 1p locus. CONCLUSIONS Including the present family, 4 families have been reported to show linkage to chromosome 1p. Statistical analysis of the audiological data shows a progression of 1 dB per octave per year in this type of progressive SNHL.