THE CLINICAL SYNDROME
There are numerous causes of the clinical syndrome called branchial plexopathy. In common to all of them is the constellation of symptoms consisting of neurogenic pain and associated weakness that radiates into the supraclavicular region and upper extremity. More common causes of branchial plexopathy include compression of the plexus by cervical ribs or abnormal muscles (e.g., thoracic outlet syndrome), invasion of the plexus by tumor (e.g., stretch injuries and avulsions), inflammatory causes (e.g., Parsonage-Turner syndrome), and postradiation plexopathy.
The pain of brachial plexopathy radiates from the shoulder and supraclavicular region into the affected upper extremity.
SIGNS AND SYMPTOMS
Patients suffering from branchial plexopathy will complain of pain radiating to the supraclavicular region and upper extremity. The pain is neuritic in character and may take on a deep, boring quality with invasion of the plexus by tumor. Movement of the neck and shoulder will exacerbate the pain, and patients suffering from brachial plexopathy will often avoid such movements in an effort to palliate the pain. Frozen shoulder often results and may confuse the diagnosis. If thoracic outlet syndrome is suspected, Adson’s test may be performed. A positive test is indicated if the radial pulse disappears with neck extended and the head turned toward the affected side. It must be noted that this test is nonspecific and treatment decisions should not be based on this finding alone. If the patient presents with severe pain that is shortly followed by profound weakness, brachial plexitis should be considered and can be confirmed with electromyography.
The Adson maneuver. The patient inhales deeply, extends the neck fully, and turns the head to the side being examined. This tests for compression in the scalene triangle and is positive if there is a diminution in the radial pulse and reproduction of the patient's symptoms.
Diseases of the cervical spinal cord, bony cervical spine, and disk can mimic branchial plexopathy. Appropriate testing including MRI and electromyography will help sort out the myriad possibilities, but the clinician should also be aware that more than one pathologic process may exist and contribute to the patient’s symptomatology. Syringomyelia, tumors of the cervical spinal cord, and tumors of the cervical nerve roots as they exit the spinal cord (e.g., schwannomas) can be of insidious onset and quite difficult to diagnosis. Pancoast’s tumor should be high on the list of diagnostic possibilities in all patients presenting with brachial plexopathy in the absence of clear antecedent trauma, especially if there is a past history of tobacco abuse. Lateral herniated cervical disk, metastatic tumor, or cervical spondylosis, which result in significant nerve root compression, may also present as a brachial plexopathy. Rarely, infection involving the apex of the lung may compress and irritate the plexus.
Gabapentin is the first-line treatment for the neuritic pain of brachial plexopathy to be considered. Start with a 300-mg dose of gabapentin at bedtime for two nights, and caution the patient about potential side effects, including dizziness, sedation, confusion, and rash. The drug is then increased in 300-mg increments, given in equally divided doses over 2 days, as side effects allow until pain relief is obtained or a total dose of 2400 mg daily is reached. At this point, if the patient has experienced partial relief of pain, blood values are measured and the drug is carefully titrated upward using 100 mg tablets. Rarely will more than 3600 mg daily be required.
This drug is useful in those patients suffering from brachial plexopathy who do not experience pain relief with gabapentin. Despite the safety and efficacy of carbamazepine compared with other treatments for brachial plexopathy, much confusion and unfounded anxiety surround its use. This medication, which may be the patient’s best chance for pain control, is sometimes discontinued due to laboratory abnormalities erroneously attributed to it. Carbamazepine should be started slowly if the pain is not out of control at a starting dose of 100 to 200 mg at bedtime for two nights. The patient should be cautioned regarding side effects, including dizziness, sedation, confusion, and rash. The drug is increased in 100- to 200-mg increments, given in equally divided doses over 2 days, as side effects allow until pain relief is obtained or a total dose of 1200 mg daily is reached.
This drug has been reported to be of value in some patients who fail to obtain relief from the aforementioned medications. Baseline laboratory tests should also be obtained before starting baclofen. The drug is increased in 10-mg increments, given in equally divided doses over 7 days s side effects allow, until pain relief is obtained or a total dose of 80 mg daily is reached.
Brachial Plexus Block
The use of brachial plexus block with local anesthetic and steroid serves as an excellent adjunct to drug treatment of brachial plexopathy. This technique rapidly relieves pain while medications are being titrated to effective levels. The initial block is carried out with preservative-free bupivacaine combined with methylprednisolone. Subsequent daily nerve blocks are carried out in a similar manner with substitution of a lower dose of methylprednisolone. This approach may also be used to obtain control of breakthrough pain.
Radiofrequency Destruction of the Brachial Plexus
The destruction of the brachial plexus can be carried out by creating a radiofrequency lesion under biplanar fluoroscopic guidance. This procedure is reserved for patients for whom all of the aforementioned treatments for brachial plexopathy have failed and whose pain is secondary to tumor or avulsion of the brachial plexus.
Dorsal Root Entry Zone Lesioning (DREZ)
This technique, which is called DREZ lesioning, is the neurosurgical procedure of choice for intractable brachial plexopathy in those patients for whom all of the aforementioned treatments for branchial plexopathy have failed and whose pain is secondary to tumor or avulsion of the brachial plexus. This is a major neurosurgical procedure and carries significant risks.
The use of physical and occupational therapy to maintain function and to help palliate pain is a crucial part of the treatment plan for patients suffering form branchial plexopathy. Shoulder abnormalities, including subluxation and adhesive capsulitis, must be aggressively searched for and treated. Occupation therapy to assist in activities of daily living is also important to avoid further deterioration of function.
The pain of brachial plexopathy is difficult to treat. It responds poorly to opioid analgesics and may respond poorly to the medications discussed. The uncontrolled pain of brachial plexopathy has led to suicide, and strong consideration should be given to the hospitalization of such patients. Correct diagnosis is crucial to successfully treat the pain and dysfunction associated with brachial plexopathy as stretch injuries and contusions of the plexus may respond with time, but plexopathy secondary to tumor or avulsion of the cervical roots will require aggressive treatment.