<unk> , also known as<unk>  malformation and<unk>  defect, is an abnormality of the inner ear that is associated with sensorineural hearing loss. This deformity was first described in 1791 by<unk>  after examining the inner ear of a deaf boy. The<unk>  describes a cochlea with incomplete partitioning and a reduced number of turns, an enlarged vestibular aqueduct and a dilated vestibule. A normal cochlea has two and a half turns, a cochlea with<unk>  has one and a half turns; the basal turns being normally formed with a dilated or cystic apical turn to the cochlear. The hearing loss can deteriorate over time either gradually or in a step-wise fashion, or may be profound from birth. Hearing loss associated with<unk>  may first become manifest in childhood or early adult life. Some children may pass newborn hearing screen to lose hearing in infancy but others present with a hearing loss at birth. Hearing loss is often progressive and because of the associated widened vestibular aqueduct may progress in a step-wise fashion associated with minor head trauma. Vestibular function is also often affected. While the hearing loss is sensorineural a conductive element may exist probably because of the third window effect of the widened vestibular aqueduct. The<unk>  can occur in cases of Pendred Syndrome and Branchio-oto-renal syndrome and in other syndromes, but can occur in non-syndromic deafness.
Mondini dysplasia
Langer mesomelic dysplasia
Thanatophoric dysplasia
Campomelic dysplasia
Mandibuloacral dysplasia
Acromicric dysplasia
Sponastrime dysplasia
Rathke's cleft cyst