Semicircular canal dysplasia
Semicircular canal dysplasia is relatively common of the labyrinthine anomalies. About 40% of patients with a malformed cochlea will have associated lateral semicircular canal (SCC) dysplasia . The other two common labyrinthine anomalies include SCC aplasia and SCC dehiscence.
In isolated SCC dysplasia, patients may have normal or near-normal hearing. However, if the cochlea is involved there may be sensorineural hearing loss. SCC dysplasia has also been associated with conductive hearing loss and vestibular symptoms .
Lateral SCC dysplasia results from disordered embryological development in the sixth week of gestation. During this time, a bud forming the SCC will form a semicircular evagination from the vestibular anlage with the central part of the pocket-shaped protrusion which adheres centrally leaving a peripheral semicircular tube. SCC dysplasia results when failed central adhesion occurs. The lateral SCC is more often deformed in this process over the posterior or superior SCC because it forms later in embryogenesis .
The typical appearance of SCC dysplasia is a broad, short and cystic space confluent with the vestibule .