This deformity was first described in 1791 by Mondini after examining the inner ear of a deaf boy.
The Mondini dysplasia describes a cochlea with incomplete partitioning and a reduced number of turns, an enlarged vestibular aqueduct and a dilated vestibule.
The hearing loss can deteriorate over time either gradually or in a step-wise fashion, or may be profound from birth.
[1] Hearing loss associated with Mondini dysplasia may first become manifest in childhood or early adult life.
While the hearing loss is sensorineural a conductive element may exist probably because of the third window effect of the widened vestibular aqueduct.