The masticatory muscles are muscle groups associated with chewing and include the biting, temporal, extrinsic and intrinsic pterygoid muscles. The muscle groups of the masticatory muscles are innervated by the trigeminal nerve. The trigeminal nerve is a mixed nerve that includes both sensory and motor fibers. The trigeminal nerve is divided into ophthalmic, maxillary and mandibular branches, where the ophthalmic and maxillary branches have only sensory fibers and the mandibular branch is divided into sensory and motor branches. When the motor branch of the mandibular branch of the trigeminal nerve is lesioned, weakness of the chewing muscles on the same side can be seen, and jaw deviation can be seen when the patient opens his mouth. Cranial magnetic resonance and trigeminal nerve magnetic resonance examination should be improved to clarify the presence of vascular disease or occupational disease.