"Rudimentary otocyst represents an anomaly that is more differentiated than complete labyrinthine aplasia but less so than common cavity. The causative insult likely occurs early in the 3rd–4th week of development, when the inner ear is in the form of the otic vesicle 2."
"There is a round or ovoid cystic space that is at most a few millimetres in diameter in the place of the inner ear 1. The internal auditory canal is absent 1. Rudimentary semicircular canals may be present 1. The bony carotid canal is absent 3."