In testing the stapedius reflex (acoustic reflex), an ipsilateral reflex arc traverses which neural pathway from the stapedius muscle to the stimulus ear?

• A CN VIII → cochlear nucleus → inferior colliculus → facial motor nucleus → CN VII
• B CN VIII → inferior colliculus → superior olivary complex → CN VII
• C CN VIII → medial geniculate body → facial motor nucleus → CN VII
• D CN VIII → cochlear nucleus → superior olivary complex → facial motor nucleus → CN VII ✓

Explanation

The acoustic (stapedius) reflex arc consists of: auditory signal via CN VIII → dorsal and ventral cochlear nuclei → bilateral projections to superior olivary complexes (SOC) → facial nerve motor nuclei bilaterally → CN VII → stapedius muscle. The ipsilateral reflex tests CN VIII afferent and CN VII efferent on the same side. The crossed reflex tests CN VIII on one side and CN VII on the contralateral side. This pathway is clinically important: an absent reflex with normal hearing suggests a CN VII lesion distal to the stapedial branch, localizing the site of facial nerve injury.

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.