A patient has diminished lacrimation on the right side and loss of taste from the anterior two-thirds of the right tongue, but has normal facial muscle movement. The lesion is most likely in the:

• A Right chorda tympani nerve proximal to its junction with the lingual nerve
• B Right geniculate ganglion
• C Right facial nerve distal to the stylomastoid foramen
• D Right facial nerve in the facial canal proximal to the origin of the greater petrosal nerve ✓

Explanation

The greater petrosal nerve (carrying parasympathetic fibers for lacrimation) arises from the facial nerve at the geniculate ganglion before the nerve descends in the facial canal. The chorda tympani (taste from anterior two-thirds of tongue + submandibular/sublingual salivary secretion) arises lower in the facial canal. A lesion in the facial canal proximal to the greater petrosal nerve origin would damage both greater petrosal and chorda tympani fibers, causing reduced lacrimation and taste loss, while motor fibers exiting at the stylomastoid foramen remain intact. A lesion at the geniculate ganglion (Ramsay Hunt syndrome) would also affect hearing.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.