Levator Ani Pain Syndrome
The primary function of the levator ani muscle is active support of the pelvic contents, compressing the urethra and vagina by elevating the pelvic floor, and maintaining a physiological anorectal angle by pulling the anorectal junction forward.
The levator ani muscle originates at the posterior surface of the body of the pubis, the fascia of the obturator internus muscle, and the ischial spine. The muscle inserts on the anococcygeal raphe and coccyx.
The muscle is innervated by the branches of the ventral primary rami of spinal nerves S3 to S4. The levator ani muscle is susceptible to trauma and to wear and tear from overuse and misuse. It may develop myofascial pain syndrome that may also be associated with gluteal bursitis and coccygodynia, which may confuse the clinical picture further.
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 anatomical areas.
This referred pain often is misdiagnosed or attributed to other organ systems, leading to extensive evaluations and ineffective treatment. Patients with levator ani syndrome exhibit a trigger point along the rectum or perineum. Taut bands of muscle fibers often are identified when myofascial trigger points are palpated. Despite this consistent physical finding in patients who have myofascial pain syndrome, the pathophysiology of the myofascial trigger point remains elusive, although many theories have been advanced.
Common to all these theories is the thought 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, a variety of other factors seem to predispose the patient to develop myofascial pain syndrome. The weekend athlete who subjects his or her body to unaccustomed physical activity often develops myofascial pain syndrome. Poor posture while sitting at a computer keyboard or while watching television also has been implicated as a predisposing factor to the development of myofascial pain syndrome. Previous injuries may result in abnormal muscle function and predispose to the subsequent development of myofascial pain syndrome. All 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 levator ani 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 may occur 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.
What are the Symptoms of Levator Ani Pain Syndrome
The trigger point is the pathognomonic lesion of myofascial pain and is thought to be the result of microtrauma to the affected muscles. This pathological 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, an involuntary withdrawal of the stimulated muscle, termed a jump sign, may occur. The jump sign also is characteristic of myofascial pain syndrome. Patients with gluteus medius syndrome exhibit a trigger point along the rectum or perineum.
How is Levator Ani Pain Syndrome diagnosed?
No specific test exists for levator ani pain syndrome. Testing is aimed primarily at identifying occult pathological conditions or other diseases that may mimic myofascial pain syndrome (see discussion of “Differential Diagnosis”). Plain radiographs help delineate bony abnormality of the pelvis and hip, including arthritis, avascular necrosis of the hip, fracture, congenital abnormalities, and tumor. All patients with recent onset of myofascial pain syndrome should undergo magnetic resonance imaging (MRI) of the lumbar spine and pelvis to rule out occult pathological processes. Screening laboratory tests, consisting of complete blood count, erythrocyte sedimentation rate, antinuclear antibody testing, and automated blood chemistry testing, should be performed to rule out occult inflammatory arthritis, infection, and tumor.
Levator ani pain syndrome is a clinical diagnosis of exclusion supported by a combination of clinical history, physical examination, radiography, ultrasound imaging, and MRI. Pain syndromes that may mimic levator ani pain syndrome include lumbosacral radiculopathy and plexopathy; stress fractures of the pelvis and hip; myofascial pain syndromes such as gluteus medius pain syndrome; pelvic floor muscle strain; inflammatory arthritis; and disorders of the lumbar spinal cord, roots, plexus, and nerves. Intrapelvic tumors also may mimic the clinical presentation of gluteus medius pain syndrome.
Levator ani pain syndrome is best treated with a multimodality approach. Physical therapy, including correction of functional abnormalities (e.g., poor posture, improper chair or computer height) and use of heat modalities and deep sedative massage, combined with nonsteroidal antiinflammatory drugs (NSAIDs) and skeletal muscle relaxants is a reasonable starting point. If these treatments fail to provide rapid symptomatic relief, local trigger point injection of local anesthetic and steroid into the myofascial trigger point area is a reasonable next step. Underlying diffuse muscle pain, sleep disturbance, and depression are best treated with a tricyclic antidepressant compound, such as nortriptyline, which can be started at a single bedtime dose of 25 mg. Pregabalin, milnacipran, and duloxetine may also provide symptomatic relief of pain and associated symptoms.
When performing trigger point injections, careful preparation of the patient before trigger point injection helps optimize results. Trigger point injections are directed at the primary trigger point, rather than in the area of referred pain. It should be explained to the patient that the goal of trigger point injection is to block the trigger of the persistent pain and, it is hoped, provide long-lasting relief. It is important that the patient understands that with most patients who have myofascial pain syndrome, more than one treatment modality is required to provide optimal pain relief. The use of the prone or lateral position when identifying and marking trigger points and when performing the actual trigger point injection helps decrease the incidence of vasovagal reactions. The skin overlying the trigger point to be injected always should be prepared with antiseptic solution before injection to avoid infection.
Complications and Pitfalls
The proximity to the rectum, vagina, and pelvic viscera makes it imperative that this procedure be performed only by clinicians well versed in the regional anatomy and experienced in performing interventional pain management techniques. Many patients also report a transient increase in pain after injection of trigger points. If long needles are used, damage to the retroperitoneal organs also may occur.
Trigger point injections are an extremely safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected. Care must be taken to use sterile technique to avoid infection and universal precautions to avoid risk to the operator. Most side effects of trigger point injection are related to needle-induced trauma to the injection site and underlying tissues. The incidence of ecchymosis and hematoma formation can be decreased if pressure is placed on the injection site immediately after trigger point injection. The avoidance of overly long needles helps decrease the incidence of trauma to underlying structures. Special care must be taken to avoid pneumothorax when injecting trigger points in proximity to the underlying pleural space. The antidepressant compounds represent the primary pharmacological treatment for myofascial pain syndrome. Tricyclic antidepressants are thought to be more effective than selective serotonin reuptake inhibitors in the treatment of this painful condition. The precise mechanism of action of the antidepressant compounds in the treatment of myofascial pain syndrome is unknown. Some investigators believe that the primary effect of this class of drugs is to treat the underlying depression that is present in many patients who have myofascial pain syndrome. Drugs such as amitriptyline and nortriptyline represent good first choices and should be given as a single bedtime dose, starting with 10 to 25 mg and titrating upward as side effects allow.