Cochlear incomplete partition type II (IP-II) is a type of inner ear malformation, specifically a cochlear incomplete partition, associated with sensorineural hearing loss. It is characterized by a cystic cochlear apex and should not be confused with Mondini anomaly, which is a historic term for the combination of incomplete partition type II, enlarged vestibule, and large vestibular aqueduct.
Radiographic features
CT
The cochlea appears to have only 1.5 turns with coalescence of the apical and middle turn to form a cystic apex 1. The basal turn is normal, while these findings affect the middle and apical turns 2:
absent interscalar septum
absent osseous spiral lamina
deficient modiolus
Incomplete partition type II is usually, but not always, associated with the extracochlear findings that contribute to the full Mondini anomaly:
enlarged vestibule
MRI
Care should be taken when interpreting MRI in isolation for cochlear incomplete partition; it should always be correlated to petrous temporal bone CT 3.
T2: on thin sections, absence of interscalar septum and spiral lamina at the level of apical and middle turns may be seen 1
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