Accessory medial pterygoid muscle

A previously undescribed accessory medial pterygoid muscle occurred uniformly in the dissection room population studied. The origin extends from the superior margin of the pterygoid plate and skirts medially of foramen spinosum and ovale, finally terminating on the carotid canal rim. The flat triangular muscle descends to insert its apex into the medial surface of the medial pterygoid muscle about 1 cm below its exit from the pterygoid fossae. Histologic examination confirmed striated muscle. Independent innervation arises from the medial surface of the mandibular nerve trunk just below the foramen ovale and enters the accessory medial pterygoid lateral surface at about the upper third, centrally. Muscle function is suggested as a discriminating action, rein-like in nature, probably corresponding to Bennett movement. Variation in size of this muscle may also explain the range observed for Bennett movement. The dental occlusal action field is suggested to be the buccal aspect of the last molar tooth.