Table 3.

Classification of cochleovestibular malformations.

Cochlear Malformations	Michel deformity: complete absence of all cochlear and vestibular structures Cochlear aplasia: cochlea is completely absent Common cavity deformity: common cystic cavity of cochlea and vestibule without differentiation Cochlear hypoplasia: cochlea and vestibule are separate, but their dimensions are smaller than normal. Hypoplastic cochlea resembles a small bud off the internal auditory canal Incomplete partition type I (IP-1): cochlea is lacking entire modiolus and cribriform area, resulting in a cystic appearance. This is accompanied by a large cystic vestibule. Incomplete partition type II (IP-2): Mondini deformity – cochlea consists of 1.5 turns instead of 2.5 turns, in which the middle and apical turns coalesce to form a cystic apex, accompanied by a dilated vestibule and enlarged vestibular aqueduct.
Vestibular malformations	Michel deformity, common cavity, absent vestibule, hypoplastic vestibule, dilated vestibule
Semicircular canal malformations	Absent, hypoplastic or enlarged
Internal auditory canal malformations	Absent, narrow or enlarged
Vestibular and cochlear aqueduct findings	Enlarged