A patient develops loss of taste from the anterior two-thirds of the tongue on the right, reduced salivation from submandibular and sublingual glands, and hyperacusis on the right, but no facial weakness. Where is the lesion in the facial nerve?

• A Below the origin of nerve to stapedius, proximal to chorda tympani ✓
• B At the geniculate ganglion (proximal to greater petrosal nerve origin)
• C Between geniculate ganglion and origin of nerve to stapedius (involving chorda tympani and stapedial nerve)
• D In the parotid gland (extratemporal)

Explanation

The lesion is below the origin of the nerve to stapedius (which causes hyperacusis when damaged) but above the origin of the chorda tympani (which carries taste from anterior 2/3 tongue and secretomotor to submandibular/sublingual glands). The absence of facial weakness indicates the main motor trunk is spared; the lesion involves only the segment between the stapedial and chorda tympani branches. At the geniculate ganglion level, lacrimation via greater petrosal nerve would also be affected. In the parotid (extratemporal), taste and salivation would not be affected.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.