Internal auditory canal

bony canal in the petrous bone, between the structures of the inner ear and the cerebellopontine angle. It contains the vestibulocochlear nerve (branching in the canal into the cochlear nerve, and the superior and inferior vestibular nerves) and the facial nerve. A vascular loop is often present near the internal aperture and may extend into the internal auditory canal (IAC). Also, see ear, Bills bar, falciform crest.

2. Pathology

Abnormal size

A unilateral wide IAC may be caused by an acoustic schwannoma. Bilateral wide IACs may be due to dural ectasia, as seen in neurofibromatosis. A wide canal may be associated with an abnormal bony partition between the canal and the inner ear; such an ear may show a gusher during surgery (see also X linked hearing loss). A very narrow canal may imply absence of the vestibulocochlear nerve, or part of it.

Other congenital lesions

- a vascular malformation head and neck may be present in the IAC; this may mimic radiologically an intracanalicular tumour.

- vestibulocochlear nerve congenital anomalies.

Inflammation

- meningeal inflammation in the IAC may originate from the middle ear, spreading through the inner ear, or may represent intracanalicular extension from meningitis in the cerebellopontine angle.

Tumours