Lateral pterygoid (also called external pterygoid) is a deep muscle located in the face and is part of the muscle group that has a primary role in chewing (mastication). It is short, flat, thick and somewhat conical in shape. Exclusively, action of lateral pterygoid results in opening of jaw. While initiating this action, several other muscles also assist the lateral pterygoid. Very few muscles in the body have more than one heads or parts and lateral pterygoid is one of them. It has two heads inserting into a bulge called condyloid process of the mandible bone. Mandible is actually the lower jaw bone which is the strongest and the largest bone in the face.
Contraction of lateral pterygoid causes depression of the mandible which results in opening of the jaw. It can also cause the forward and side movements of the mandible. All of these movements are essential in chewing food (mastication).
Clinical Importance – Associated Diseases/Conditions
Lateral pterygoid muscle is prone to tenderness resulting in the derangement of temporomandibular joint (TMJ) and playing a role in some other conditions that briefly described below.
Temporomandibular Joint (TMJ) Dysfunction:
Lateral pterygoid muscle has been a point of focus in some cases of TMJ impairment. The superior head of the muscle is often involved triggering pain around the joint that can radiate to maxilla bone. Hyperactivity or spasm of the muscle has been established as the origins of this condition and can lead to displacement of the anterior disk of the joint. It can be very painful during chewing when the tongue and food is pressed against the muscle. Usually, treatment may include only pain killers.
Lateral Pterygoid Dystonia (Neuromuscular Dysfunction):
Sustained or repetitive use of the lateral pterygoid can cause the concerned mandible pushed off to one side, giving an asymmetrical facial structure. Other reasons of this dysfunction include myositis (inflammation), spasms or nutritional imbalances. Common symptoms of Lateral pterygoid dystonia include abnormal posture and pain, and can cause functional impairments in speech, chewing and swallowing of the patient. Treatment may include muscle relaxants, physiotherapy, Botox injections, and so on.
Myofacial Syndrome of Lateral Pterygoid:
This condition is rare and comprises of pain and tenderness of the concerned side, particularly anterior to the ear and occasionally into the temple. Dry needling technique is available, which according to one study is very effective in treating this condition. However, conventional treatment employs injecting local anesthetics or corticosteroids to suppress or reduce the pain.