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Stapedius Detail

musculus stapedius detail

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.

Nerve: Facial nerve — stapedial branch (VII) Blood Supply: Posterior tympanic artery Region: Head & Skull

Anatomical Data

Origin, Insertion & Supply

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

Biomechanics

Function & Actions

Actions	Tilts the stapes to reduce its transmission of vibration — the acoustic reflex; Protects the inner ear from loud sounds — especially low frequencies

Clinical Relevance

Clinical Notes

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.

Palpation

Not palpable — assessed by acoustic reflexometry and tympanometry.

Pathology

Common Injuries & Conditions

Stapedius Acoustic Reflex in Facial Nerve Monitoring

Real-time stapedius acoustic reflex monitoring during posterior fossa surgery to provide immediate feedback on facial nerve integrity before visible movement is detectable.