Some medical professionals refer to Parsonage-Turner syndrome (PTS) as acute brachial neuropathy or neuralgic amyotrophy. A now defunct term, as idiopathic brachial plexopathy, refers to the idiopathic nature of the condition — it lacks a known cause. There are many risk factors of PTS but experts still lack a clear understanding of why some people develop it while the vast majority of the population does not, despite experiencing the same factors. Each year, doctors identify approximately 1.6 cases of PTS out of 100,000 people.

Etiology

Parsonage-Turner syndrome is a rare condition with a specific set of symptoms most likely triggered by autoimmune inflammation of the brachial plexus, a network of nerves transmitting impulses to the arms, shoulders, and chest. Sometimes PTS impacts the scapulothoracic nerve in the upper arm and shoulder, which leads to scapular winging — wherein the shoulder blade extends from the back in an abnormal position. This can lead to difficulty lifting and pulling, and basic day-to-day actions.

Initial Symptoms

The most significant symptom of Parsonage-Turner syndrome is the sudden development of continuous, severe shoulder girdle pain on only one side of the body. The pain can extend into the arm, forearm, and hand. Pain is usually worse at night and frequently causes people to wake up while sleeping; it usually lasts one or two weeks but can last longer. Sensory deficits may accompany this symptom, but this is uncommon.

Later Symptoms

In many cases of Parsonage-Turner syndrome, weakness occurs days or weeks after the initial pain. Some theories state weakness may occur immediately, but as the pain prevents people from using the muscles, affected individuals fail to notice it. Most people notice this symptom within a month, however, while numbness and muscle atrophy or wasting becomes apparent shortly after. Extreme cases may result in paralysis.

Risk Factors

Often, people report specific conditions shortly before noticing symptoms of PTS. Illness or infection due to bacteria, parasites, and viruses are common. Other correlating factors include surgery or anesthesia administration with or without a surgical procedure. Autoimmune illnesses such as rheumatic disease, connective tissue disorders, and lupus preceded about ten percent of PTS diagnoses. Immunizations, trauma, and stressful exercise also appear to coincide.

Immune Theory

The most common risk factor for developing Parsonage-Turner syndrome is a recent viral illness. Almost a quarter of people diagnosed with PTS report a viral illness immediately before symptoms of PTS start. The second most common risk factor is immunization. As such, some researchers theorize PTS develops from the immune response to certain viral illnesses or the viral antigen of vaccinations. They tend to blame the immune response rather than the virus itself because the immune system responds similarly whether the disease or an immunization meant to prevent the disease triggers it.

Diagnosing Parsonage-Turner Syndrome

Doctors diagnose Parsonage-Turner syndrome with clinical observation. Incorrect diagnoses are common, especially in the absence of the primary identifying symptom of constant pain for a week or more. Training dictates the doctor should consider PTS if the patient reports any kind of shoulder girdle pain. MRI scans can supply additional information, and electromyograms (EMG) and nerve conduction studies (NCS) can also deliver a definitive diagnosis.

Treatment

Pain management is most important in the first few weeks of PTS. NSAIDs and opiates are the most common prescription medications. Acupuncture and transcutaneous electrical nerve stimulation — TENS — sometimes help relieve pain. Oral steroids are an option, but studies find them less than effective for most people. Immunotherapy can offer considerable aid to those with significant peripheral neuropathy symptoms.

Physical Therapy

Physical therapy is essential after the initial pain symptoms fade or are under control. Doctors can institute a more aggressive therapeutic treatment plan once the pain abates. They will plan the timing and the desired result of strengthening exercises based on a patient’s degree of muscle atrophy and nerve involvement and may also schedule occupation therapy. Electrical stimulation can treat severe numbness or paralysis, but must be used with great care.

Surgical Intervention

Muscle grafts and surgery are last resort treatments for Parsonage-Turner syndrome, and are most common for young adult or athlete patients. Complications of physical or occupational therapy can occur in otherwise young and healthy people if lingering numbness and nerve damage lead to a muscle imbalance. Muscles that are not receiving signals and functioning as they should prompt other muscle groups to overcompensate. Failing to catch this situation early makes returning muscles and nerves to a healthy state more difficult, which may call for surgical intervention.

Prognosis

Muscle wasting and other effects of Parsonage-Turner syndrome last an average of 18 to 24 months, but most people do recover. Age is the biggest factor in healing time. A six-year-old child may exhibit symptoms for only six months while those over 50 could exhibit symptoms for years.