Section Editor: Sandy Cheng-Yu Chen, M.D.
Taipei Medical University Hospital, Taipei, Taiwan
Mondini malformation is part of the spectrum of inner ear congenital abnormalities and curses with sensorineural hearing loss. It is characterized by a triad of findings: 1) abnormal cochlea with only 1.5 turns owing to the confluence of the apical and middle turn, forming a cystic apex (cochlear incomplete partition type II) (A–C, yellow arrows); 2) enlarged vestibule (A and C, white arrows) with normal semicircular canals; and 3) enlarged vestibular aqueduct with a dilated endolymphatic sac (A and C, orange arrows). This disorder can occur in association with other anomalies (Klippel-Feil syndrome, DiGeorge syndrome, Pendred syndrome) or in isolation. Apart from sensorineural hearing loss, patients have an increased risk of meningitis and spontaneous CSF otorrhea.