ABSTRACT
X-linked deafness type III (DFN3) is most often characterized by mixed conductive and sensorineural deafness associated with a perilymphatic gusher upon stapedectomy (McKusick, 1998). However, there is variability of the phenotype among pedigrees with some patients demonstrating sensorineural deafness alone (Bitner-Glindzicz et al., 1994; Bitner-Glindzicz et al., 1995). DFN3 is the most common form of X-linked deafness, and constitutes between 1 and 2% of congenital deafness in humans (Nance et al., 1971). In DFN3 patients in which an exploratory tympanotomy has been performed, perilymphatic gusher is associated with removal or even disturbance of the stapes (Cremers et al., 1985; Glasscock, 1973; Nance et al., 1971). The stapes footplate in these patients lacks the annular rim of the stapes footplate (Glasscock, 1973; Nance et al., 1971), which is formed from the otic capsule during development (Anson et al., 1960). Although some patients demonstrate stapes fixation, others demonstrate brisk acoustic reflexes, suggesting that the conductive component of hearing loss may be due to mechanisms other than stapes fixation (Cremers, 1985; Cremers et al., 1985). Radiological examination typically demonstrates a bulbous enlargement of the internal auditory meatus (IAM) at its lateral extent (Glasscock, 1973; Phelps et al., 1991). Additional radiological features include small cochleae, enlarged vestibule, and reduced diameter of the semicircular canals (Cremers et al., 1985; Phelps et al., 1991). A reduction of vestibular function in affected individuals has been demonstrated (Cremers et al., 1985; Phelps et al., 1991).
