From OMIM
DFNB4 with enlarged vestibular aqueduct is characterized by pre- or perilingual onset of sensorineural or mixed hearing loss, which may be fluctuating or progressive. The hearing loss is associated with temporal bone abnormalities, most commonly enlargement of the vestibular aqueduct, but it can also include the more severe Mondini dysplasia, a complex malformation in which the normal cochlear spiral of 2.5 turns is replaced by a hypoplastic coil of 1.5 turns (summary by Campbell et al., 2001 and Pryor et al., 2005). Enlarged vestibular aqueduct is the most common form of inner ear abnormality and can be associated with disequilibrium symptoms in a minority of patients (Valvassori, 1983; Jackler and de la Cruz, 1989; Levenson et al., 1989; Arcand et al., 1991; Belenky et al., 1993; Okumura et al., 1995).  http://www.omim.org/entry/600791