A patient with an inflammatory lesion in the facial canal develops complete ipsilateral lower motor neuron facial palsy with a dry eye and reduced tearing. Taste and salivation are also impaired. At what level is the lesion?

• A Distal to the stylomastoid foramen
• B Between the geniculate ganglion and the origin of the nerve to stapedius
• C Distal to the origin of the chorda tympani
• D Proximal to the origin of the greater petrosal nerve ✓

Explanation

Lacrimation depends on preganglionic fibers that leave the facial nerve at the geniculate ganglion as the greater petrosal nerve. A lesion proximal to this point abolishes tearing along with taste and salivation, because fibers to the chorda tympani have not yet branched off either. A lesion distal to the stylomastoid foramen spares taste, salivation, and lacrimation entirely, which rules out option A. Dry eye therefore localizes the lesion to the labyrinthine segment or at the geniculate ganglion.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.