Presentation
Bilateral hearing loss and ataxia for one year.
Patient Data
Bilateral superior and posterior semicircular canals are normal in appearance and caliber bilaterally.
Normal bilateral lateral semicircular canals are not seen. Fusion of right vestibule and right lateral semicircular canal to form the dilated dysplastic lateral semicircular canal with dysplastic right vestibule. Absence of normal bony island within the right semicircular canal.
The lumen of anterior and posterior arms of left lateral semicircular canal are dilated with internal septation seen within the loop.
Normal two and half turns of both cochlea noted.
The membranous labyrinth signal intensities within both cochlea and semicircular canals are normal.
Bilateral 7th and 8th nerves are visualized within the cisterns and internal auditory canals and normal in caliber.
No abnormal enhancing lesions seen within the both cerebellopontine angles and internal auditory canals to suggest schwannomas.
No enlargement of vestibular aqueducts.
Type II left anterior inferior cerebellar artery vascular loop entering the left IAC but less than 50% of length. No obvious vascular contact of this loop to the left cochlear nerve.
A few non specific hyperintense foci on T2WI and FLAIR sequences in bilateral centrum semiovale and corona radiata.
Case Discussion
Bilateral lateral semicircular canal vestibule dysplasia. These anomalies can present with normal hearing, sensorineural hearing loss , conductive hearing loss or mixed hearing loss as well as imbalance. Studies have not shown any consistent relationship between LSC bony island hypoplasia and hearing loss.
The lateral SCC is more often deformed in this process over the posterior or superior SCC because it forms later in embryogenesis
Type II AICA vascular loop (left side). Clinical correlation required to assess the significance of this loop, no obvious contact point seen with the nerve in left IAM.