The stapedius is the smallest named muscle in the human body (1 mm long). Its facial nerve supply means it is the key muscle for intraoperative facial nerve monitoring during posterior fossa and ear surgery — its acoustic reflex is monitored to confirm facial nerve integrity.
| Origin | Posterior wall of the middle ear — pyramidal eminence on the posterior tympanic cavity wall |
|---|---|
| Insertion | Neck of the stapes |
| Nerve Supply | Facial nerve — stapedial branch (VII) |
| Blood Supply | Posterior tympanic artery |
| Actions | Tilts the stapes to reduce its transmission of vibration — the acoustic reflex; Protects the inner ear from loud sounds — especially low frequencies |
|---|
Stapedius acoustic reflex testing is a standard audiological assessment — absent reflex indicates facial nerve, middle ear, or cochlear pathology depending on the pattern. Stapedius myoclonus produces a rhythmic clicking tinnitus. Bell's palsy abolishes the ipsilateral acoustic reflex — its early return during recovery indicates proximal facial nerve regeneration.
Not palpable — assessed by acoustic reflexometry and tympanometry.
Real-time stapedius acoustic reflex monitoring during posterior fossa surgery to provide immediate feedback on facial nerve integrity before visible movement is detectable.
