What is Parsonage Turner syndrome?
Parsonage Turner syndrome is an acute brachial plexus neuritis, commonly also affecting the long thoracic, musculocutaneous, and axillary nerves.
It causes patchy upper extremity weakness and numbness, usually accompanied by pain.
Parsonage Turner syndrome is a neuritis involving nerves originating from the brachial plexus, with the suprascapular nerve most commonly involved.
As with the nerve impingement syndromes, MRI findings include high T2-weighted signal intensity within the muscle (from acute denervation) or fatty atrophy (from chronic denervation) involving one or more of the rotator cuff muscles or deltoid muscles.
Symptoms are bilateral in 20% of patients.
This condition is associated with diabetes, systemic lupus erythematosus, and polyarteritis nodosa and may follow immunizations or viral infections.
One-third of patients recover within 1 year and 90% within 3 years.
Parsonage and Turner described the painful condition of the shoulder and upper extremity that bears their name and was first identified as a distinct clinical entity in 1948.
It is also known by a number of other names, including Kiloh-Nevin syndrome, idiopathic brachial plexopathy, and paralytic brachial neuritis. The pain of Parsonage Turner syndrome is of acute onset and is severe in intensity.
The pain is burning and involves the shoulder and upper arm, preceding the onset of muscle weakness by hours to days.
Sleep disturbance is common, and weakness of the muscles of the shoulder and upper extremity, including the deltoid, infraspinatus, supraspinatus, and biceps, occurs as the syndrome progresses. In some patients, this weakness can be severe, progressing to complete flaccidity.
A viral cause of Parsonage-Turner syndrome has been suggested, as has the belief that this painful condition is an immunological disease.
Neither theory has been proven, although two patients on anti–programmed cell death-1 checkpoint inhibitor therapies developed the syndrome.
What are the Symptoms of Parsonage Turner syndrome
Patients with Parsonage Turner syndrome first experience a sudden onset of pain that begins in the shoulder and radiates down the arm. The pain is severe and is followed by the development of weakness.
The skin examination is normal, with no evidence of acute herpes zoster. Range of motion of the cervical spine generally does not affect the pain or numbness, in contrast to cervical radiculopathy.
Weakness of the muscles of the shoulder and upper extremity, including the deltoid, infraspinatus, supraspinatus, and biceps, increases as the syndrome progresses. Scapular winging may be present.
Flaccidity of these muscles may occur. Usually, more than one portion of the brachial plexus is affected, although isolated single-nerve involvement can occur.
Brachial plexopathy has many causes. 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 brachial 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., Pancoast syndrome), direct trauma to the plexus (e.g., stretch injuries and avulsions), inflammatory causes (e.g., Parsonage-Turner syndrome), and postradiation plexopathy.
Cervical radiculopathy is a much more common cause of upper extremity pain and weakness relative to Parsonage-Turner syndrome.
The below table differentiates these two painful conditions. In patients in whom Parsonage-Turner syndrome affects only an isolated nerve, the syndrome may be misdiagnosed as entrapment neuropathy.
Electromyography is the cornerstone in sorting out the differential diagnosis in patients with the acute onset of shoulder and upper extremity pain.
Comparison of Parsonage Turner Syndrome and Cervical Radiculopathy
|Parsonage-Turner syndrome||Acute, intense burning pain that begins spontaneously in shoulder and upper arm; pain unaffected by neck movement||Neurological deficits that suggest more than one nerve is involved; weakness that may progress to flaccidity||Electromyogram positive for brachial plexopathy; MRI of cervical spine noncontributory to diagnosis|
|Cervical radiculopathy||Pain begins in neck and radiates down arm; the pain is increased by neck movement; pain and muscle weakness occur spontaneously||Weakness and numbness in the distribution of a single nerve root||MRI of cervical spine reveals herniated disc or osteophyte formation or both|
Diseases of the cervical spinal cord, bony cervical spine, and disc can mimic Parsonage-Turner syndrome.
Appropriate testing, including magnetic resonance imaging (MRI) and electromyography, helps sort out the myriad possibilities, but the clinician also should be aware that more than one pathological process may coexist and contribute to the patient’s symptoms.
Syringomyelia, tumors of the cervical spinal cord, and tumors of the cervical nerve roots as they exit the spinal cord, such as schwannomas, can be of insidious onset and quite difficult to diagnose.
Pancoast tumor should be high on the list of diagnostic possibilities in all patients with brachial plexopathy in the absence of clear antecedent trauma, especially in the presence of a history of tobacco abuse.
Lateral herniated cervical disc, metastatic tumor, or cervical spondylosis that results in significant nerve root compression also may manifest as a brachial plexopathy. Rarely, infection involving the apex of the lung may compress and irritate the plexus.
How is Parsonage Turner Syndrome diagnosed?
All patients presenting with Parsonage-Turner syndrome must undergo MRI of the cervical spine and the brachial plexus.
Computed tomography (CT) is a reasonable second choice if MRI is contraindicated.
Electromyography and nerve conduction velocity testing are extremely sensitive, and a skilled electromyographer can help delineate the specific portion of the plexus that is abnormal.
If an inflammatory basis for the plexopathy is suspected, serial electromyography is indicated.
If Pancoast tumor or other tumors of the brachial plexus are suspected, chest radiographs with apical lordotic views may be helpful.
Screening laboratory tests consisting of complete blood cell count, erythrocyte sedimentation rate, antinuclear antibody testing, and automated blood chemistry testing should be performed if the diagnosis of brachial plexopathy is in question, to help rule out other causes of pain.
Gabapentin is the first-line treatment for the neuritic pain of Parsonage-Turner syndrome. The drug is started with a 300-mg dose at bedtime for 2 nights; the patient should be cautioned about potential side effects, including dizziness, sedation, confusion, and rash.
The drug is 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 per day is reached. At this point, if the patient has experienced partial pain relief, blood values are measured, and the drug is carefully titrated upward using 100-mg tablets. More than 3600 mg daily rarely is required.
Carbamazepine is useful in patients with Parsonage-Turner syndrome who do not experience pain relief with gabapentin. Despite the safety and efficacy of carbamazepine compared with other treatments for Parsonage Turner syndrome, much confusion and unfounded anxiety surround its use.
This medication, which may be the best chance for pain control, is sometimes discontinued because of laboratory abnormalities erroneously attributed to it. Baseline screening laboratory tests, consisting of a complete blood cell count, urinalysis, and automated chemistry profile, should be obtained before starting the drug.
Carbamazepine should be started slowly if the pain is not out of control.
The drug is started with a 100- to 200-mg dose at bedtime for 2 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.
Careful monitoring of laboratory parameters is mandatory to avoid the rare possibility of life-threatening blood dyscrasia.
At the first sign of blood count abnormality or rash, carbamazepine should be discontinued. Failure to monitor patients started on carbamazepine can be disastrous because aplastic anemia can occur.
When pain relief is obtained, the patient should be kept at that dosage of carbamazepine for at least 6 months before considering tapering of this medication. The patient should be informed that under no circumstances should the dosage of drug be changed or the drug refilled or discontinued without the physician’s knowledge.
Baclofen has been reported to be valuable in some patients who fail to obtain relief from gabapentin and carbamazepine. Baseline laboratory tests should be obtained before starting baclofen.
The drug is started with a 10-mg dose at bedtime for 2 nights; the patient should be cautioned about potential adverse effects, which are the same as those of carbamazepine and gabapentin.
Baclofen is increased in 10-mg increments, given in equally divided doses over 7 days, as side effects allow, until pain relief is obtained or a total dose of 80 mg per day is reached. This drug has significant hepatic and central nervous system side effects, including weakness and sedation.
As with carbamazepine, careful monitoring of laboratory values is indicated during the initial use of this drug.
When treating patients with any of the drugs mentioned, the physician should inform the patient that premature tapering or discontinuation of the medication may lead to the recurrence of pain. The pain becomes more difficult to control thereafter.
Brachial Plexus Block
The use of brachial plexus block with a local anesthetic and steroid is an excellent adjunct to drug treatment of Parsonage-Turner syndrome. This technique rapidly relieves pain while medications are being titrated to effective levels. The initial block is performed with preservative-free bupivacaine combined with methylprednisolone.
Subsequent daily nerve blocks are done in a similar manner, substituting a lower dose of methylprednisolone. This approach also may be used to obtain control of breakthrough pain.
Ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications.
The use of physical and occupational therapy to maintain function and help palliate pain is a crucial part of the treatment plan for patients with Parsonage Turner syndrome.
Shoulder abnormalities, including subluxation and adhesive capsulitis, must be aggressively searched for and treated. Occupational therapy to assist in activities of daily living also is important to avoid further deterioration of function.
The pain of Parsonage Turner syndrome is difficult to treat. It responds poorly to opioid analgesics and may respond poorly to the previously mentioned medications. The uncontrolled pain of Parsonage-Turner syndrome has led to suicide, and hospitalization of such patients should be strongly considered. Correct diagnosis is crucial to successfully treat the pain and dysfunction associated with brachial plexopathy because stretch injuries and contusions of the plexus may respond with time, but plexopathy secondary to tumor or avulsion of the cervical roots requires aggressive treatment.
Brachial plexus block with a local anesthetic and steroid represents an excellent stop gap measure for patients with the uncontrolled pain of Parsonage Turner syndrome while waiting for pharmacological treatments to take effect.
As mentioned, correct diagnosis is paramount to allow the clinician to design a logical treatment plan.