Presentation
Sudden right-sided hearing loss 7 years ago. Initial MRI 6 years ago. Thought to be labyrinthitis. No improvement and now vertigo for follow-up.
Patient Data
Subtle but definite asymmetrical enhancement of the right basal turn of the cochlea and modiolus.
Mass lesion with abnormal enhancement involving the cochlea, vestibule and components of the VIIIth nerve at the apex of the internal auditory canal.
Case Discussion
Most "acoustic' schwannomas arise in the vestibular nerve at the vestibular ganglion that is at the junction of the central and peripheral myelin (in the fundus of the IAC). Schwannomas can actually occur anywhere along the canal where there are Schwann cells supporting peripheral myelin but can involve the membranous labyrinth i.e. cochlea, vestibule, or semicircular canals where there are also peripheral nerves. These are known as labyrinthine schwannomas and are quite rare.
In this case, the very early finding of enhancement without mass effect in the modiolus and basal turn of the cochlea has been interpreted as an inflammatory process but over time the true tumourfactive nature of a schwannoma has been revealed.