STABLE AND PROGRESSIVE HEARING-LOSS IN TYPE 2A USHERS SYNDROME

Audiograms were traced or additionally performed on 23 Usher's syndrom e patients in 10 Dutch multi-affected families, all linked to chromoso me Iq(USH2A locus). Serial audiograms, available in 13 patients, were used for a regression analysis of binaural pure tone average on age (f ollow-up, 9 to 32 years) to test for ''significant progression,'' ie, a significant regression coefficient, here called the ''annual thresho ld increase'' (ATI, expressed in decibels per year). A significant ATT (>1 dB/y) was observed in 3 patients. Analysis of variance of An demo nstrated significant heterogeneity; hearing loss was either stable or progressive. This implies a significant clinical heterogeneity. A simi lar analysis performed on our progressive USH2A cases and ''type III'' cases previously reported by others (ATI of 1 to 5 dB/y), some of whi ch were recently linked to chromosome 3q (USH3 locus), failed to show any significant heterogeneity in the progression of hearing loss.