Internal acoustic meatus
Exit foramen · CN VII CN VIII
A canal in the petrous temporal bone opening into the posterior cranial fossa at the cerebellopontine angle. VII with the nervus intermedius and VIII enter it together with the labyrinthine artery; VIII ends in the inner ear while VII continues into the facial canal towards the stylomastoid foramen.
Traced from the start
- Pons
- Facial nerve (CN VII)Vestibulocochlear nerve (CN VIII)
- Internal acoustic meatus
Detail
- Transmits
- Facial nerve (VII) with nervus intermedius, vestibulocochlear nerve (VIII), labyrinthine artery (from the anterior inferior cerebellar or basilar artery)
- Opens into
- Posterior cranial fossa at the cerebellopontine angle, where V, VII and VIII are all within reach of an expanding mass
When it goes wrong
Vestibular schwannoma arising inside the meatus and expanding it
Progressive unilateral sensorineural deafness and tinnitus before any facial weakness, because VII tolerates slow stretch; expansion into the cerebellopontine angle then adds V and VII signs
Transverse fracture of the petrous temporal bone crossing the meatus and otic capsule
Immediate lower motor neurone facial palsy with profound sensorineural deafness and vertigo; the commoner longitudinal fracture instead causes conductive loss with haemotympanum and, less often, a delayed facial palsy
Practise this structure
4 questions in the bank tagged Cranial Nerves.
A 52-year-old woman has had two months of numbness over the right forehead, the right upper eyelid and the tip of her nose, with a gritty feeling in the right e…
Foundations · middle twist
A 44-year-old man has had 18 months of worsening hearing on the left with constant ringing in that ear. He still follows conversation in a quiet room but cannot…
Foundations · middle twist
A 58-year-old man has sudden vertigo and a hoarse voice, and chokes when he drinks. The palate elevates to the right and there is no gag response when the left…
Foundations · middle twist
A 27-year-old man was struck on the head at football a week ago. He now sees two images, one above the other, worst when reading or going down stairs. The verti…
Foundations · middle twist