Narrow internal auditory meatus: an idiopathic case confirming the origin and pathway of vestibular evoked myogenic potentials in humans.

OBJECTIVE

To confirm the origin and pathway of vestibular evoked myogenic potentials (VEMPs) in humans.

DESIGN

Case study.

SETTING

University hospital.

PATIENT: A patient with a narrow internal auditory meatus (IAM).

MAIN OUTCOME MEASURES: Imaging studies and functional studies concerning the seventh and eighth cranial nerves.

RESULTS

Of the 4 nerves in the IAM, all but the cochlear nerve had normal function and normal courses, despite the pronounced narrowing of the IAM. The facial nerve had a normal diameter, but the vestibular nerves were thinner. Imaging revealed that the cochlear nerve was absent or extremely thinned. Both the cochlea and the cochlear nerve showed no function in the affected ear, although the VEMPs were evoked normally.

CONCLUSION

Our results definitively support the vestibular origin of VEMPs in humans.