The auricularis posterior is one of the three extrinsic ear muscles (with auricularis anterior and superior), all of which are vestigial in most humans. It arises from the mastoid process and attaches to the posterior ear cartilage. In most people voluntary movement is absent, though some individuals retain voluntary control of all three auricular muscles. The muscle is innervated by the posterior auricular branch of the facial nerve, one of the earliest branches given off by CN VII as it exits the stylomastoid foramen.
| Origin | Mastoid process of the temporal bone via two or three fleshy slips |
|---|---|
| Insertion | Posterior surface of the cartilage of the auricle (pinna) |
| Nerve Supply | Posterior auricular branch of the facial nerve (CN VII) |
| Blood Supply | Posterior auricular artery |
| Actions | Draws the auricle posteriorly and slightly upward (vestigial in most humans) |
|---|
The posterior auricular nerve and muscle serve as electrophysiological landmarks in facial nerve testing. The posterior auricular nerve is the first branch tested in facial nerve conduction studies, stimulated at the mastoid tip with recording over the auricularis posterior muscle. Assessment of this branch helps localise facial nerve lesions relative to the stylomastoid foramen. Auricularis posterior is also electrically tested in electrodiagnosis to distinguish supranuclear from infranuclear facial weakness.
The muscle is rarely palpable in isolation. It may be felt by placing a finger directly posterior to the ear on the mastoid surface while the patient attempts voluntary ear movement.
Loss of auricularis posterior function is assessed by the posterior auricular nerve conduction study, helping localise Bell palsy or traumatic facial nerve lesions relative to the stylomastoid foramen, with intact posterior auricular response suggesting a more distal lesion.
