In topognostic testing of facial nerve palsy, a patient has absent stapedial reflex, absent taste to the anterior 2/3 tongue, but normal lacrimation. The lesion is most likely located:

• A At the stylomastoid foramen (extratemporal)
• B In the mastoid (vertical) segment, between the nerve to stapedius and chorda tympani origins ✓
• C In the tympanic (horizontal) segment, distal to the geniculate ganglion
• D At the geniculate ganglion (above greater petrosal nerve origin)

Explanation

Facial nerve topognosis: Greater petrosal nerve (lacrimation) arises at geniculate ganglion. Nerve to stapedius arises in the mastoid segment above chorda tympani. Chorda tympani (taste, salivation) arises 6mm above stylomastoid foramen. Here: normal lacrimation (greater petrosal intact, lesion below geniculate), absent stapedial reflex (nerve to stapedius affected), absent taste (chorda tympani affected) → lesion is between the nerve to stapedius and chorda tympani origins — i.e., upper mastoid segment.

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.