A patient with a right-sided acoustic neuroma (vestibular schwannoma) undergoes the Schirmer test, stapedial reflex testing, and taste testing to localize facial nerve involvement. The Schirmer test (lacrimation) is normal but taste on the anterior 2/3 of tongue is impaired. The lesion is located:

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

Explanation

The greater superficial petrosal nerve (GSPN) carrying parasympathetic fibres to the lacrimal gland arises at the geniculate ganglion. Normal Schirmer test indicates intact GSPN (proximal facial nerve function preserved). Taste to the anterior 2/3 of the tongue is carried by the chorda tympani, which arises from the facial nerve in the vertical mastoid segment. Impaired taste with normal lacrimation places the lesion between the geniculate ganglion and the chorda tympani origin — the tympanic (horizontal) and proximal vertical 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.