The auricularis posterior is a facial muscle that holds in place the outer part of the ear. The auricularis posterior originates at the mastoid process and receives its nerve supply from the facial nerves. The auricularis posterior inserts into the auricle root's posterior position. It consists of two fasciculi that are connected through aponeurotic fibers to the mastoid of the temporal bone. During facial paralysis, the auricularis posterior may undergo microscopic changes, including changes in fiber size, abnormalities in fiber distribution, changes in the sub-sarcolemmal nuclei, and cellular reactions. These changes are mostly due to the immediate effects of the paralysis, rather than muscular atrophy through denervation. The auricularis posterior may be useful for evaluating hearing sensitivity. Auricularis posterior muscle responses are similar to auditory blink reflexes in testing effectiveness. A recent study has shown that auricularis posterior muscle responses were a useful addition to regular electrophysiological methods for objective assessment of hearing. Over half the subjects had a muscular response to normal frequencies under least optimal testing conditions.