Medial pterygoid is a quadrilateral muscle and just like lateral pterygoid, it is also involved in chewing (mastication). It is also called internal pterygoid muscle. However, in contrast to lateral pterygoid, medial pterygoid performs mandibular elevation that results in closing of lower jaw. Its fibers insert into the angle of the mandible, which happens to be the largest bone of the face.
When the fibers of medial pterygoid contract on both sides of the face, they pull the lower jaw up, hence closing the jaws together, especially when it occurs during the process of chewing. It also has a small role in placing the lower jaw forward. When the medial pterygoid contracts unilaterally, it causes a lateral movement of the mandible which helps in the grinding action in chewing.
Clinical Importance – Associated Diseases/Conditions
Medial Pterygoid Trismus (Myospasm):
It is featured as the difficulty in opening of jaws usually following a typical dental anesthesia given locally where the needle has to pass through the medial pterygoid muscle. This condition is called a dental trismus and may last for two weeks. Although a medial pterygoid trismus can also arise from a hematoma of this muscle in which blood clots within the tissues. It can be painful and may swell up as a result of an inflammation.
Blunt Trauma to the Cheek:
In addition to the buccinator muscle receiving a blow, for e.g. in an accident or a fight, medial pterygoid muscle can also be damaged. It results in hematoma formation, leading to inflammation. Typical symptoms are extreme pain, swelling, redness, and warmth. Also a temporary functional disability during mastication due to pain.
Myofascial Pain of Medial Pterygoid:
The trigger points within the muscle may cause pain that refers to the overlying skin. Usually the pain radiates to mouth, throat and ear. The pain is of diffused type, as compared to lateral pterygoid which occurs in precisely smaller area. Added problems such as difficulty in swallowing and restriction to jaw openings also occur. Massaging the area can help reduce pain, however, pain killers are the treatment of choice since this condition can go away with time.