Chest wall pain syndromes are commonly encountered in clinical practice. Some occur with relatively greater frequency and are more readily identified by the clinician, such as costochondritis and Tietze syndrome.
Others occur so infrequently that they are often misdiagnosed, resulting in a suboptimal outcome. Sternalis syndrome is one such infrequent cause of anterior chest wall pain. Sternalis is a constellation of symptoms affecting the midline anterior chest wall that can radiate to the retrosternal area and the medial aspect of the arm.
Sternalis syndrome can mimic the pain of myocardial infarction and is frequently misdiagnosed as such. Sternalis syndrome is a myofascial pain syndrome and is characterized by trigger points in the midsternal area. In contrast to costosternal syndrome, which also manifests as midsternal pain, the pain of sternalis syndrome is not exacerbated by movement of the chest wall and shoulder. The intensity of the pain associated with sternalis syndrome is mild to moderate and described as having a deep, aching character. The pain of sternalis syndrome is intermittent.
What are the Symptoms of Sternalis Syndrome
On physical examination, a patient with sternalis syndrome exhibits myofascial trigger points at the midline over the sternum. Occasionally, a coexistent trigger point is located in the pectoralis muscle or sternal head of the sternocleidomastoid muscle.
Pain is reproduced with palpation of these trigger points, rather than movement of the chest wall and shoulders. A positive jump sign is present when these trigger points are stimulated. Trigger points at the lateral border of the scapula also may be present and amenable to injection therapy. As mentioned, movement of the shoulders and chest wall does not exacerbate the pain.
How is Sternalis Syndrome diagnosed?
Plain radiographs are indicated in all patients thought to have sternalis syndrome to rule out occult bony pathological processes, including metastatic lesions. Based on the patient’s clinical presentation, additional tests, including complete blood cell count, prostate-specific antigen level, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated.
Computed tomography (CT) and magnetic resonance imaging (MRI) of the chest are indicated if a retrosternal mass, such as thymoma, is suspected, as well as to help confirm the presence of a sternalis muscle or other anterior chest wall mass.
Ultrasound imaging may help further characterize the nature of masses involving the anterior chest wall. Electromyography is indicated in patients with sternalis syndrome to help rule out cervical radiculopathy or plexopathy that may be considered because of the referred arm pain.
Injection of the sternalis muscle with a local anesthetic and steroid serves as a diagnostic and therapeutic maneuver.
As mentioned earlier, the pain of sternalis syndrome is often mistaken for pain of cardiac origin and can lead to visits to the emergency department and unnecessary cardiac workups. If trauma has occurred, sternalis syndrome may coexist with fractured ribs or fractures of the sternum itself, which can be missed on plain radiographs and may require radionucleotide bone scanning for proper identification.
Tietze syndrome, which is painful enlargement of the upper costochondral cartilage associated with viral infections, can be confused with sternalis syndrome, as can costosternal syndrome and congenital abnormalities of the sternum.
Neuropathic pain involving the chest wall also may be confused or coexist with costosternal syndrome. Examples of such neuropathic pain include diabetic polyneuropathies and acute herpes zoster involving the thoracic nerves.
The possibility of diseases of the structures of the anterior chest wall and mediastinum is ever present, and these diseases sometimes can be difficult to diagnose. Pathological processes that inflame the pleura, such as pulmonary embolus, infection, and tumor, also should be considered.
Initial treatment of sternalis syndrome should include a combination of simple analgesics and nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors. Local application of heat and cold also may be beneficial to provide symptomatic relief of the pain of sternalis syndrome.
The use of an elastic rib belt may help provide symptomatic relief in some patients. For patients who do not respond to these treatment modalities, injection of the trigger areas located in the sternalis muscle using a local anesthetic and steroid may be a reasonable next step. Ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications.
The major problem in the care of patients thought to have sternalis syndrome is the failure to identify potentially serious pathological conditions of the thorax, mediastinum, or both. Given the proximity of the pleural space, pneumothorax after injection of the sternalis muscle is a possibility, as is injury to the mediastinal and intrathoracic structures. Approximately 25% of patients report a transient increase in pain after this injection technique and should be warned about this.
Patients with sternalis syndrome often present to the emergency department, fearing they are having a heart attack. The syndrome also is misdiagnosed frequently as cervical radiculopathy secondary to the referred arm pain. Electromyography helps delineate the cause and extent of neural compromise.
The injection technique is extremely effective in the treatment of sternalis syndrome. Coexistent costosternal or manubriosternal arthritis also may contribute to anterior chest wall pain and may require additional treatment with a more localized injection of a local anesthetic and depot steroid. This technique is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected. Pneumothorax can be avoided if shorter needles are used and the needle is not advanced too deeply. Care must be taken to use sterile technique to avoid infection, and universal precautions should be taken to avoid risk to the operator. The incidence of ecchymosis and hematoma formation can be decreased if pressure is placed on the injection site immediately after injection. The use of physical modalities, including local heat and gentle range-of-motion exercises, should be introduced several days after the patient undergoes this injection technique for shoulder pain. Vigorous exercises should be avoided because they would exacerbate symptoms. Simple analgesics and NSAIDs may be used concurrently with this injection technique.