Following a longitudinal fracture of the temporal bone, a man has right lower motor neuron facial palsy with hyperacusis and a strikingly dry right eye. Reduced lacrimation localises the nerve injury to which segment of the facial nerve?

• A Distal to the origin of the nerve to stapedius
• B Between the pyramidal eminence and the stylomastoid foramen
• C At or proximal to the geniculate ganglion ✓
• D Within the parotid gland branches

Explanation

The greater petrosal nerve, carrying secretomotor fibers to the lacrimal gland via the pterygopalatine ganglion, arises from the facial nerve at the geniculate ganglion at the first genu. A lesion must be at or above this point to abolish lacrimation. Lesions distal to the geniculate, such as at the second genu or stylomastoid foramen, may cause hyperacusis and facial weakness but leave tearing intact, which is what excludes those sites here.

Reference: Snell's Clinical Anatomy, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.