Muscle Referred Pain:

The primary and secondary muscles of mastication must be evaluated during a comprehensive evaluation. Muscles are one of the most frequent sources of reported pain, but the diagnosis often requires a comprehensive palpation and/or injections of trigger point areas to complete the diagnosis. Travel and Simon’s Text Myofascial Pain and Dysfunction, The Trigger Point Manual is an outstanding text to learn about these situations.

The temporalis muscle is one of the primary muscles of mastication. Palpation of the anterior temporalis is demonstrated in these slides and a pain referral pattern is depicted in the diagram to the right. Although the actual etiology of trigger points is not completely understood, there are precipitating factors that are related to some trigger points.

Trigger points in the temporalis feel like a small nodule beneath the fingers and the skull. Palpation of acute trigger points usually causes a pain sensation for the patient. Chronic trigger points (present greater than 6 months) may not cause an immediate pain sensation, but continued stimulation can cause a chronic trigger point to become acute and painful.

The temporalis muscle (especially the anterior 1/3) is used in approximating the mandible to the maxilla. One should evaluate the possibility of clenching or bruxing if this muscle is found to contain dysfunctional trigger point areas.

Palpation of the masseter is completed by palpating both right and left superficial and deep masseter to evaluate the presence of trigger points. This muscle will very frequently have trigger points as it is related to most mandibular elevation movements. Trigger points in these regions refer pain to adjacent structures, the teeth and more distant sites, like above/behind the eye. Palpation of the trigger points may or may not cause the referred site pain.

Palpation of the internal or medial pterygoid exerts a pressure in the body of the muscle. Pain in the region of the muscle would usually indicate the muscle is not functioning in a normal manner, but may have trigger points that can refer pain as demonstrated in the diagram on the right. These diffuse referral pain patterns make the diagnosis of internal / medial pterygoid difficult and a local delivery of a anesthetic may be necessary to adequately diagnose internal / medial pterygoid dysfunction.

Palpation of the lateral or external pterygoid is not possible, but palpation of the region is possible as depicted in the photograph on the left. The referral pattern of pain from trigger points in the external pterygoid is illustrated in the right diagram. A differential diagnosis of a trigger point in the external pterygoid would require injection of Carbocaine or similar diagnostic substance into the muscle and an evaluation of the pain pattern.

The anterior neck musculature is responsible for opening movements of the mandible and support of the head/cervical spine during closure. These muscles are directly involved with mandibular movements and can become dysfunctional if there is an imbalance between the joint, bite and muscle relationship.

The sternocleidomastoid is a supportive muscle that functions in response to mandibular/ maxillary movements. Palpation of this muscle is possible and the presence of trigger points is easy to discern as they are tender and palpably distinct. Referred pain is depicted in the diagram on the right and demonstrates a very diffuse pain pattern, even to the contralateral side. Diagnosis of myogenic origin pain requires a careful evaluation of the source and referral site.

The upper posterior cervical musculature is responsible for head posture and counteracts all mandibular movements to maintain the cranium in a stable relationship as the mandible opens and closes. The muscles of this region are secondary muscles of mastication as these muscles are utilized to support jaw function. Trigger points in these secondary muscles of mastication are referred to a specific region as depicted in the diagram on the right. Palpation of these muscles should not elicit pain and there should not be any tenderness during mandibular, head and neck motion.

The lower posterior cervical musculature is also palpated by squeezing the muscle between the thumb and first finger. Trigger points are easily discovered and are able to refer pain to the locations depicted on the diagram on the right. These muscles must counterbalance all mandibular movements to maintain the cranium in a stable postural relationship.

The trapezium attaches to the base of the skull and extends down much of the length of the upper back to the thoracic region. This muscle is used to maintain a stable head relationship during mandibular function as well as its normal upper quadrant movement functions. Trigger points in this muscle refer pain to the regions demonstrated in the composite pain reference diagram. Trigger points in these regions can be palpated by the bi-digital technique demonstrated above, or by digital pressure to the muscle where the trigger point is discerned in the muscle mass.

There are other perpetuating factors that can be related to trigger point dysfunction. The viewer is encouraged to review Travel and Simon as a general reference for these matters.