Acute brachial plexus neuritis is an uncommon inflammatory condition of the nerves in the shoulder. It leads to severe shoulder and upper arm pain followed by marked
upper arm weakness. Brachial neuritis occurs in about 1 to 2 cases per 100,000 persons, but this figure is probably low because many cases may be misdiagnosed,
or the symptoms are mild and clinically unrecognized.
Symptoms include sudden, intense, sharp, throbbing or burning pain in the shoulder and upper arm with no apparent cause. The pain is constant, but made worse
by moving the shoulder. In most patients, the pain subsides over the ensuing days to weeks, to be replaced by a subsequent weakness in the upper arm -
at times to the point of muscle limpness.
Brachial neuritis is generally thought to be an autoimmune inflammatory reaction against nerves that run from the neck to the upper arm. The symptoms may occur
3 to 14 days after a viral infection, bacterial infection, or rarely, vaccination. In even rarer cases, symptoms have occurred after surgery, trauma or other illnesses.
An MRI may show a decrease in muscle mass in the affected area and helps rule out other causes. Likewise, tests of nerves and muscles
(such as nerve conduction studies or an electromyogram) might be considered to confirm nerve involvement and to rule out other conditions.
The pain is treated with common pain relievers or narcotics, based on severity. Several weeks of pain management may be required. Physical therapy
for up to 8 weeks is often needed to help maintain strength and mobility. High dose oral steroids have also sometimes used.
The course of the neuritis is usually one of gradual improvement and recovery of muscle strength in 3 to 4 months. Full recovery of muscle strength may
take up to 2 to 3 years. Some patients, however, may have several years of muscle weakness or a slight permanent weakness.