<unk>  is thought to result from failure of development of the otic placode, due to developmental arrest at the third week of gestation. The common cavity deformity, a confluence of illdefined cochlea and vestibular organ results from a disruption during the fourth and fifth week. An arrest in fifth or sixth week of gestation result in cochlear<unk>  or cochlear hypoplasia respectively. Associations Abnormal development of the skeletal portions of the second arch # Nondifferentiation of the stapes, with resultant absence of round and oval window. # Abnormal course of the facial nerve. Skull base abnormalities # Hypoplasia of the petrous temporal bone. # Hypoplastic and sclerotic petrous apex may mimic labyrinthitis ossificans. # Platybasia. # Aberrant course of jugular veins.
Michel aplasia
Micromastia
Synechia 
Desmoplasia
Brachyphalangy
Microtia
Cartilage–hair hypoplasia
Pulmonary hypoplasia