M11- A2 Internal Auditory Canal

2. Vertical crest in fundus of the internal auditory canal is known as :

a. Bill's bar.

b. Ponticulus.

c. Cog.

d. Falciform crest.

The internal auditory canal is the bony channel in the posterior fossa, that houses the facial (VII), cochlear and vestibular (VIII) nerves. At the fundus it is split horizontally by the falciform or transverse crest. The superior portion of the canal above the transverse crest is again split into anterior and posterior parts by vertical crest or Bill's bar.

It is used as a surgical landmark for facial nerve identification during translabyrinthine surgery.



Contents of the Internal Auditory Canal


7.Up = Cranial nerve 7 ("7-up, coke down")
BB = The Bill bar
Coke = Cochlear nerve ("7-up, coke down")
IVN = Inferior vestibular nerve
SVN = Superior vestibular nerve
TC = Transverse crest

Answer: a. Bill's bar.