The tensor tympani muscle is innervated by the medial pterygoid nerve (a branch of the mandibular nerve V3), but its tendon crosses the middle ear to insert on the handle of malleus. The stapedius muscle, which dampens loud sounds, is innervated by:

• A Glossopharyngeal nerve (IX)
• B Chorda tympani (branch of facial nerve)
• C Facial nerve (VII) via the nerve to stapedius from the mastoid segment ✓
• D Tympanic branch of glossopharyngeal nerve (Jacobson's nerve)

Explanation

The stapedius muscle is the smallest skeletal muscle in the human body and is innervated by the nerve to stapedius, a branch of the facial nerve (CN VII) that arises from the mastoid (second genu) segment of the facial nerve within the facial canal. Facial nerve palsy results in absence of the stapedial reflex (acoustic reflex absent) and hyperacusis due to lost stapedial dampening. Jacobson's nerve (tympanic branch of IX) carries parasympathetic fibres to the parotid.

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.