each hand over the muscle and ask the patient to clench his or her teeth several times. Pathology The masseter muscle can become enlarged in patients who habitually clench or grind (with bruxism) their teeth and even in those who constantly chew gum. This masseteric hypertrophy is asymptomatic and soft; it is usually bilateral but can be unilateral. Even if the hypertrophy is bilateral, asymmetry of the face may still occur due to unequal enlargement of the muscles. This extraoral enlargement may be confused with parotid salivary gland disease, dental infections, and maxillofacial neoplasms. However, no other signs are present except those involved in changes in occlusion intraorally such as pain, and the enlargement corresponds with the outline of the muscle. Most patients seek medical attention because of comments about facial appearance, and this situation may be associated with further pathology of the temporomandibular joint. Finally, the muscle undergoes spasm with malignant hyperthermia as do other skeletal muscles, but this one is easily noted, since it is on the face. Singers often experience various kinds of masseter tension, which is often treated with transdermal massages or stretches as a vocal warm-up. In other animals The masseter muscle's positioning is a distinguishing feature of hystricognathous creatures such as mole-rats, where it passes partially through the infraorbital foramen and connects to the bone on the opposite side. Additional images See also Zygomasseteric system Notes References Muscles of the head and neck