Mondini malformation is a historical term used to describe an incomplete partition type II anomaly with large vestibular aqueduct.


The term is often used inappropriately to describe any cochlear abnormality, rather than a specific type of cochlear hypoplasia. Thus, most would favor not using the term, except perhaps in cases where the findings exactly match those described by Mondini.
If any doubt it is best to just describe the anatomical abnormalities.

Clinical presentation

Patients have sensorineural hearing loss, which is usually bilateral. As the basal turn of the cochlea is intact, high-frequency hearing is generally preserved.


The abnormality is thought to result from a relatively late insult during the 7 week of embryological development when most of the inner ear has already formed. Earlier insults result in more severe abnormalities (Michel deformitycochlear aplasia and cochlear hypoplasia).

See classification of congenital cochlear anomalies.

There are only 1.5 turns to the cochlea instead of the expected 2.5. The interscalar septum between the middle and apical segments also fails to form leading to a confluent, sac-like cochlea.


Mondini dysplasia has been associated with thalidomide and rubella embryopathies as well as a number of syndromes:

Some publications have suggested a link between Mondini malformation and spontaneous CSF fistulae and meningitis; however, this appears to be only the case with more severe forms of cochlear hypoplasia, and not with a true isolated Mondini malformation .

Radiographic features

The Mondini abnormality consists of a triad :

  • abnormal cochlea
    • only 1.5 turns (instead of the normal 2.5 turns)
    • normal basal turn with a cystic apex in place of the distal 1.5 turns
  • enlarged vestibule with normal semicircular canals
  • enlarged vestibular aqueduct containing a dilated endolymphatic sac
  • Additionally, complete or partial absence of the normal interscalar septum is also present, which can now be demonstrated on high-field MRI .

    Treatment and prognosis

    Hearing can be improved by implantation of a multichannel cochlear implant .


    There is an increased risk of:

    History and etymology

    It was first described in Latin by Carlo Mondini (1729-1803), an Italian anatomist, in 1791 .

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