During drilling for vestibular schwannoma excision, the surgeon follows the facial nerve from the fundus of the internal acoustic meatus. At which landmark does the labyrinthine segment end by turning sharply posteriorly?

• A Geniculate ganglion ✓
• B Stylomastoid foramen
• C Pyramidal eminence
• D Facial hiatus

Explanation

The facial canal has three segments. The short labyrinthine segment runs anterolaterally from the meatal fundus and ends at the geniculate ganglion, where the nerve makes the sharp first genu, turning posteriorly to become the tympanic segment. The facial hiatus on the arcuate eminence transmits the greater petrosal nerve leaving the ganglion, the pyramidal eminence relates to the second genu and stapedius tendon, and the stylomastoid foramen is the terminal exit, far distal to the turn described.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.