In the surgical anatomy of the facial nerve in the temporal bone, which segment of the facial nerve is LONGEST?

• A Mastoid (vertical) segment ✓
• B Meatal (internal auditory canal) segment
• C Labyrinthine segment
• D Tympanic (horizontal) segment

Explanation

The facial nerve in the temporal bone has four segments: meatal (~8–10 mm), labyrinthine (~4 mm, narrowest canal — most vulnerable to ischemia in Bell's palsy), tympanic/horizontal (~12 mm), and mastoid/vertical (~15–20 mm, the longest). The mastoid segment descends from the second genu to the stylomastoid foramen and is the segment most at risk during mastoid surgery. The labyrinthine segment has the narrowest bony canal, explaining why it is the critical site of ischemic compression in Bell's palsy.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.