what causes pain in upper arm muscle
Pain is unaltered by neck or arm movements. Pain is spontaneous, often with no apparent cause. Gradual decrease in pain followed by marked weakness of upper arm. Neurologic deficits indicate that more than one nerve is involved (i.e., lesion in the plexus).
Patients with acute brachial plexus neuritis are often misdiagnosed as having cervical radiculopathy. Acute brachial plexus neuritis is an uncommon disorder characterized by severe shoulder and upper arm pain followed by marked upper arm weakness. The temporal profile of pain preceding weakness is important in establishing a prompt diagnosis and differentiating acute brachial plexus neuritis from cervical radiculopathy.