Indications and Clinical Considerations
The sternocleidomastoid is particularly susceptible to the development of myofascial pain syndrome. Flexion–extension and lateral motion stretch injuries to the neck or repeated microtrauma secondary to jobs that require working overhead for long periods, such as painting ceilings, or activities such as reading in bed or watching television while reclining on a couch, may result in the development of myofascial pain in the sternocleidomastoid muscle.
Myofascial pain syndrome is a chronic pain syndrome that affects a focal or regional portion of the body. The sine qua non of myofascial pain syndrome is the finding of myofascial trigger points on physical examination. Although these trigger points generally are localized to the regional part of the body affected, the pain of myofascial pain syndrome often is referred to other anatomic areas. This referred pain often is misdiagnosed or attributed to other organ systems, leading to extensive evaluations and ineffective treatment. Patients with myofascial pain syndrome involving the sternocleidomastoid often have referred pain into the upper neck, face, angle of the mandible, and temporal region ( Figure 20-1 ).
The trigger point is the pathognomonic lesion of myofascial pain and is thought to be the result of microtrauma to the affected muscles. This pathologic lesion is characterized by a local point of exquisite tenderness in affected muscle. Mechanical stimulation of the trigger point by palpation or stretching produces not only intense local pain but also referred pain. In addition to this local and referred pain, there often is an involuntary withdrawal of the stimulated muscle, called a “jump sign.” This jump sign also is characteristic of myofascial pain syndrome.
Taut bands of muscle fibers often are identified when myofascial trigger points are palpated. In spite of this consistent physical finding in patients with myofascial pain syndrome, the pathophysiology of the myofascial trigger point remains elusive, although many theories have been advanced. Common to all of these theories is the belief that trigger points are the result of microtrauma to the affected muscle. This microtrauma may occur as a single injury to the affected muscle or may occur as the result of repetitive microtrauma or chronic deconditioning of the agonist and antagonist muscle unit.
In addition to muscle trauma, various other factors seem to predispose the patient for developing myofascial pain syndrome. The weekend athlete who subjects his or her body to unaccustomed physical activity may develop myofascial pain syndrome. The poor posture of someone sitting at a computer keyboard or watching television has also been implicated as a predisposing factor to the development of myofascial pain syndrome. Previous injuries may result in abnormal muscle function and predispose the patient to the subsequent development of myofascial pain syndrome. All of these predisposing factors may be intensified if the patient also has poor nutritional status or coexisting psychological or behavioral abnormalities, including chronic stress and depression. The sternocleidomastoid muscle seems to be particularly susceptible to stress-induced myofascial pain syndrome.
Stiffness and fatigue often coexist with the pain of myofascial pain syndrome, increasing the functional disability associated with this disease and complicating its treatment. Myofascial pain syndrome may occur as a primary disease state or in conjunction with other painful conditions, including radiculopathy and chronic regional pain syndromes. Psychological or behavioral abnormalities, including depression, frequently coexist with the muscle abnormalities associated with myofascial pain syndrome. Treatment of these psychological and behavioral abnormalities must be an integral part of any successful treatment plan for myofascial pain syndrome.