Neuralgic Amyotrophy
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Description
Neuralgic amyotrophy is also called Parsonage-Turner syndrome, brachial neuritis, and brachial plexitis. In response to bodily stress (e.g., surgery, flu, unusually excessive exercise, post-vaccination), the brachial plexus, branches of the brachial plexus, or other upper (rarely lower) extremity nerves may develop idiopathic inflammation. The exact cause is unknown. This inflammation is quite painful, which limits use of the arm. As the pain slowly resolves over a few days or weeks, the patient now notices paralysis and a variable degree of numbness in the shoulder and arm. The amount of paralysis varies, with unusually severe cases having complete arm paralysis. Weakness and numbness slowly resolves over time. This may take many months, or even 1-3 years. Although most people improve, the arm may not return to normal and remain partially paralyzed. Brachial plexitis may involve nerves controlling almost any muscle, however, nerves to the shoulder, scapula, and forearm are more commonly affected.
Anatomy
The following nerves may be affected (unilateral or bilateral): brachial plexus, long thoracic nerve, anterior interosseous nerve, posterior interosseous nerve, suprascapular nerve, lumbosacral plexus, and others). Histologically there is an inflammation involving the nerve with variable axonal injury and demyelination. The inflammation is predominantly lymphocytes found endoneurally, and/or perivascular in the epineurium.
Clinical Presentation
As mentioned above, classically patients present with the sudden onset of suprascapular and shoulder pain days to a few weeks after a bodily stess. Although neurological deficit is rarely present initially, the shoulder often is immobilizaed by the patient secondary to pain. A days, or a week or two later, the pain subsides and is replaced by progressive atrophy and weakness of the affected muscles. Sensory disturbances can occur but are often not pronounced. Neuralgic Amyotrophy may be confused with intraoperative positional injuries, or other nerve injuries from surgery. However, neuralgic amyotrophy usually occurs days after surgery and often involves a nerve remote from the operative field. This condition may be recurrent and even be inherited (rare).
Diagnosis
Diagnosis is obtained by history and physical examination, and by excluding all other possible causes. Electrical testing is useful for both diagnosis as well as determining prognosis. Usually a more diffuse process is documented with electrical testing than is present clinically, including bilateral involvement. Scapular winging is common.
Treatment
Treatment is mostly symptomatic; steroids and other anti-inflammatory medications have been used without proven benefit. During the first few days, pain control is prioritized. Once the acute pain has mostly resolved, gentle and progressive physical therapy is started, which promotes range of motion and subsequent recovery. Surgery is rarely indicated, however, in select cases with severe deficits lacking any clinical or electrical recovery by about six months, neurolysis and/or nerve transfers may be an option. Nerve biopsy is rarely indicated and does not usually modify treatment.
Outcome
Complete return to normal strength may occur in a matter of weeks to years. 5-10% of patients do not recover, or partially recover, being left with residual weakness and atrophy. 5-10% of patients have recurrent episodes, which may cause additive deficits. If another immediate family member has had a similar episode, then hereditary neuralgic amyotrophy may be present (5% of cases).
