Brachioradialis Syndrome

Brachioradialis Syndrome

Anatomy and Function of Brachioradialis muscle

The brachioradialis muscle flexes the forearm at the elbow, pronates the forearm when supinated, and supinates the forearm when pronated. It originates at the upper lateral supracondylar ridge of the humerus and the lateral intermuscular septum of the humerus. The muscle inserts on the superior aspect of the styloid process of the radius, the lateral side of the distal radius, and the antebrachial fascia. The muscle is innervated by the radial nerve.

The brachioradialis muscle is susceptible to the development of myofascial pain syndrome. This pain is most often the result of repetitive microtrauma to the muscle from such activities as turning a screwdriver, prolonged ironing, repeated flexing of the forearm at the elbow (e.g., when using exercise equipment), handshaking, or digging with a trowel. Tennis injuries caused by an improper one-handed backhand technique have also been implicated as an inciting factor in myofascial pain syndrome, as has blunt trauma to the 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 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 brachioradialis muscle often have referred pain in the ipsilateral forearm and, on occasion, above the elbow.

The trigger point is the pathognomonic lesion of myofascial pain syndrome and 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, is often seen and is characteristic of myofascial pain syndrome. Patients with brachioradialis syndrome have a trigger point over the superior belly of the muscle.

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 result from microtrauma to the affected muscle. This trauma may occur 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 brachioradialis 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.

What are the symptoms of Brachioradialis syndrome?

The trigger point is the pathologic lesion of brachioradialis syndrome, and it is characterized by a local point of exquisite tenderness in the brachioradialis muscle. This trigger point can best be demonstrated by having the patient simultaneously flex and pronate the forearm against active resistance. Point tenderness over the lateral supracondylar ridge of the humerus may also be present and may be amenable to injection therapy.

Mechanical stimulation of the trigger point by palpation or stretching produces both intense local pain and referred pain. The jump sign is also characteristic of brachioradialis syndrome, as is pain over the brachioradialis muscle that radiates from the lateral epicondyle and superior portion of the muscle into the forearm.

How is this condition diagnosed?

Biopsies of clinically identified trigger points have not revealed consistently abnormal histologic features. The muscle hosting the trigger points has been described either as “moth-eaten” or as containing “waxy degeneration.” Increased plasma myoglobin has been reported in some patients with brachioradialis syndrome, but this finding has not been corroborated by other investigators. Electrodiagnostic testing of patients suffering from brachioradialis syndrome 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 brachioradialis syndrome.

Differential Diagnosis

The diagnosis of brachioradialis syndrome is made on the basis of clinical findings rather than specific laboratory, electrodiagnostic, or radiographic testing. For this reason, a targeted history and physical examination, with a systematic search for trigger points and identification of a positive jump sign, must be carried out in every patient suspected of suffering from brachioradialis syndrome. The clinician must rule out other coexisting disease processes that may mimic brachioradialis syndrome, including primary inflammatory muscle disease and collagen vascular disease. Radiographic testing, including magnetic resonance imaging, can help identify coexisting pathologic processes such as internal derangement of the elbow, tumor, bursitis, tendinitis, crystal deposition diseases, and tennis elbow. Electromyography can rule out cubital and radial tunnel syndromes. The clinician must also identify coexisting psychological and behavioral abnormalities that may mask or exacerbate the symptoms associated with brachioradialis syndrome.

How is this condition treated?

Treatment is focused on blocking the myofascial trigger and achieving prolonged relaxation of the affected muscle. Because the mechanism of action is poorly understood, an element of trial and error is often required when developing a treatment plan. Conservative therapy consisting of trigger-point injections with local anesthetic or saline solution is the starting point. Because underlying depression and anxiety are present in many patients suffering from brachioradialis syndrome of the cervical spine, the administration of antidepressants is an integral part of most treatment plans. Pregabalin and gabapentin have also been shown to provide some palliation of the symptoms associated with fibromyalgia. Milnacipran, a serotonin-norepinephrine reuptake inhibitor has also shown to be effective in the management of fibromyalgia. The synthetic cannabinoid nabilone has also been used to manage fibromyalgia in selected patients who have failed to respond to other treatment modalities.

In addition, several adjuvant methods are available for the treatment of fibromyalgia of the cervical spine. The therapeutic use of heat and cold is often combined with trigger-point injections and antidepressants to achieve pain relief. Some patients experience decreased pain with the application of transcutaneous nerve stimulation or electrical stimulation to fatigue the affected muscles. Exercise may also provide some palliation of symptoms and reduce the fatigue associated with this disease. The injection of minute quantities of botulinum toxin type A directly into trigger points has been used with success in patients who have not responded to traditional treatment modalities.

What are the Complications?

Trigger-point injections are extremely safe if careful attention is paid to the clinically relevant anatomy. Sterile technique must be used to avoid infection, along with universal precautions to minimize any risk to the operator. Most complications of trigger-point injection are related to needle-induced trauma at the injection site and in underlying tissues. The incidence of ecchymosis and hematoma formation can be decreased if pressure is applied to the injection site immediately after injection. The avoidance of overly long needles can decrease the incidence of trauma to underlying structures. Special care must be taken to avoid damage to the underlying neural structures when injecting trigger points in proximity to the elbow and forearm.

Clinical Pearls

Although brachioradialis syndrome is a common disorder, it is often misdiagnosed. Therefore, in patients suspected of suffering from brachioradialis syndrome, a careful evaluation to identify underlying disease processes is mandatory. Brachioradialis syndrome commonly coexists with various somatic and psychological disorders.


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