cystic cochleovestibular malformation
Pre- and
post-operative imaging of cochlear implants: a pictorial review. A 1-year-old male patient, with bilateral severe SNHL from birth. HRCT axial image (left image) shows incomplete partition type I with cystic cochlea (C) and vestibulum (V). The horizontal segment of the facial nerve (arrow) is lateralized. HRCT coronal image (right image) shows an interrupted line corresponding to the most lateral aspect of the vertical segment of the facial nerve (open arrow) lateral to the continuous line corresponding to the most lateral bony aspect of the lateral semicircular canal. The normal location of the vertical segment is medial to the lateral semicircular canal
Cochlear incomplete partition type I (IP-I) is a type of cochlear anomaly associated with sensorineural hearing loss.
Radiographic features
CT
As with other types of incomplete partition, the cochlea is clearly differentiated from the vestibule and the external dimensions of the cochlea are nearly normal.
The following are the defining CT features of incomplete partition type I, leading to the name cystic cochleovestibular malformation :
- cystic appearance of the cochlea due to
- absence of the modiolus including the base/cribriform plate between the cochlea and internal auditory canal (although a thin plate not visible on imaging may be present )
- absence of the interscalar septum
- grossly dilated vestibule
This appearance has been likened to a figure 8 morphology .
Several features have been associated but are not universal:
- no large vestibular aqueduct (with exceptions )
- internal auditory canal enlargement (with exceptions )
- semicircular canal dysplasia (with exceptions )
Differential diagnosis
- common cavity: the cochlea and vestibule are also cystic but they are not separated
- incomplete partition type II: the cochlear apex is also cystic but the basal turn is distinctly formed and the vestibule is less dilated
See also
Siehe auch:
