The auricularis posterior is a facial muscle that holds the outer part of the ear in place. It originates at the mastoid process, a section of the skull just behind the ear, and receives its nerve supply from the facial nerve. The auricularis posterior inserts into the auricle root's back portion.
During facial paralysis, the auricularis posterior may undergo microscopic changes, including changes in fiber size, abnormalities in fiber distribution, and cellular reactions. These changes are mostly due to the immediate effects of the paralysis, rather than muscular decline that occurs as a result of the loss of nerve supply.
The auricularis posterior may be useful for evaluating hearing sensitivity. When tested, this muscle’s responses can reveal hearing abilities in a way similar to auditory blink reflexes, which are a person’s impulse to blink in reaction to a strong, sudden sound. Research has shown that auricularis posterior muscle responses were a useful addition to regular methods for assessment of hearing. Over half the subjects in one study had a muscular response to normal frequencies, even under imperfect testing conditions.