Abstract
The levator ani muscle is susceptible to the development of myofascial pain syndrome. Such pain is often the result of repetitive microtrauma to the muscle during such activities as mountain biking and horseback riding. Injury to the muscle during childbirth or blunt trauma to the muscle may also incite levator ani myofascial pain syndrome. 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 are generally localized to the part of the body affected, the pain is often referred to other areas. This referred pain may be misdiagnosed or attributed to other organ systems, thus leading to extensive evaluation and ineffective treatment. Patients with myofascial pain syndrome involving the levator ani muscle have primary pain in the pelvic floor that may be referred to the posterior buttocks and posterior lower extremity.
Keywords
levator ani syndrome, rectal pain, pelvic pain, trigger point, myofascial pain, fibromyalgia, jump sign, sleep disturbance, tricylic antidepressants, pregablin
ICD-10 CODE M79.7
The Clinical Syndrome
The levator ani muscle is susceptible to the development of myofascial pain syndrome. Such pain is often the result of repetitive microtrauma to the muscle during such activities as mountain biking and horseback riding ( Fig. 96.1 ). Injury to the muscle during childbirth or blunt trauma to the muscle may also incite levator ani myofascial pain syndrome ( Fig. 96.2 ).
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 are generally localized to the part of the body affected, the pain is often referred to other areas. This referred pain may be misdiagnosed or attributed to other organ systems, thus leading to extensive evaluation and ineffective treatment. Patients with myofascial pain syndrome involving the levator ani muscle have primary pain in the pelvic floor that may be referred to the posterior buttocks and posterior lower extremity ( Fig. 96.3 ).
The trigger point, a pathognomonic lesion of myofascial pain syndrome, is characterized by a local point of exquisite tenderness in the affected muscle. Mechanical stimulation of the trigger point by palpation or stretching produces not only intense local pain but also referred pain. In addition, involuntary withdrawal of the stimulated muscle, called a jump sign, often occurs and is characteristic of myofascial pain syndrome. Patients with levator ani syndrome have a trigger point along the rectum or perineum.
Taut bands of muscle fibers are often identified when myofascial trigger points are palpated. Despite this consistent physical finding, the pathophysiology of the myofascial trigger point remains elusive, although trigger points are believed to be caused by microtrauma to the affected muscle. This trauma may result from a single injury, repetitive microtrauma, or chronic deconditioning of the agonist and antagonist muscle unit.
In addition to muscle trauma, various other factors seem to predispose patients to develop myofascial pain syndrome. For instance, a weekend athlete who subjects his or her body to unaccustomed physical activity may develop myofascial pain syndrome. Poor posture while sitting at a computer or while watching television has also been implicated as a predisposing factor. Previous injuries may result in abnormal muscle function and lead to the development of myofascial pain syndrome. All these predisposing factors may be intensified if the patient also suffers from poor nutritional status or coexisting psychological or behavioral abnormalities, including chronic stress and depression. The levator ani muscle seems to be particularly susceptible to stress-induced myofascial pain syndrome.
Stiffness and fatigue often coexist with pain, and they increase the functional disability associated with this disease and complicate 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, and management of these psychological disorders is an integral part of any successful treatment plan.
Signs and Symptoms
The trigger point, the pathognomonic lesion of levator ani syndrome, is characterized by a local point of exquisite tenderness in the levator ani muscle. Mechanical stimulation of the trigger point by palpation or stretching produces primary pain in the pelvic floor and referred pain in the posterior buttocks and posterior lower extremity (see Fig. 96.3 ). In addition, the jump sign is often present.
Testing
Biopsies of clinically identified trigger points have not revealed consistently abnormal histologic features. The muscle hosting the trigger point has been described either as “moth-eaten” or as containing “waxy degeneration.” Increased plasma myoglobin has been reported in some patients with levator ani syndrome, but this finding has not been corroborated by other investigators. Electrodiagnostic testing has revealed an increase in muscle tension in some patients, but again, this finding has not been reproducible. Because of the lack of objective diagnostic testing, the clinician must rule out other coexisting disease processes that may mimic levator ani syndrome (see “ Differential Diagnosis ”). Imaging modalities, including computed tomography, magnetic resonance imaging, and ultrasound, should be considered if the diagnosis of levator ani syndrome is in question (see Figs. 96.2 and 96.4 ).
