Cochleahypoplasie

Cochlear hypoplasia is a group of inner ear malformations defined by a smaller than normal cochlea with various internal architectural abnormalities such as having <2 turns.

Epidemiology

Cochlear hypoplasia accounts for 15% of cochlear malformations .

Radiographic features

According to the classification of Sennaroglu, there are four radiographically defined types of cochlear hypoplasia . In each type, the cochlea is a structure located at the end of the internal auditory canal, lucent on CT and fluid signal on MRI, that is overall smaller than normal.

• CH-I: bud-like cochlea
  • round/ovoid and small cochlea, with absent modiolus and interscalar septa
• CH-II: cystic hypoplastic cochlea
  • similar external shape to a normal cochlea but smaller, with defective modiolus and interscalar septa
• CH-III: cochlea with <2 turns
  • similar external shape to a normal cochlea but shorter and fewer turns, with present but short modiolus and reduced total length of the interscalar septum
• CH-IV: cochlea with hypoplastic middle and apical turns
  • normal basal turn but small middle and apical turns located more anterior and medial than normal

Additional extracochlear findings are variably associated:

• cochlear nerve often hypoplastic or absent
• cochlear nerve canal: absent, narrow or normal
• vestibule and semicircular canals are usually malformed but may be normal
• internal auditory canal: normal or narrow
• vestibular aqueduct: normal or large

Differential diagnosis

• incomplete partition also features abnormal internal architecture of the cochlear and clear differentiation from the vestibule, but the cochlea has a normal-sized external contour

Siehe auch:

• Mondini-Dysplasie
• Anomalien der Cochlea