There are many causes of neck, shoulder and arm pain. Often the cause can be found in the neck where the nerves leave the spinal cord to innervate the arms. However, these nerves can also be affected by other compression syndromes, inflammation or injury as they course from the neck to the arm.
Parsonage-Turner Syndrome or Brachial Plexitis can cause symptoms such as shoulder pain, arm pain, loss of sensation, paresthesias and/or weakness in the affected arm. These symptoms are very similar to symptoms patients experience with neck pathology. However, the problem arises in the proximal shoulder where the brachial plexus is located, not in the cervical spine. The brachial plexus is a complex network of nerves that innervate the arm to provide movement and sensation. It is located in the lateral neck and proximal part of the shoulder.
Many times there is no known associated injury or illness that causes brachial plexitis. Other times it can be triggered by a viral illness or an autoimmune response to a vaccination.
Fortunately, most patients will make a very good recovery with only supportive treatment. Treatments may include steroids, neuropathic medications such as Gabapentin and physical therapy. The diagnosis can be difficult and is often made by a neurosurgeon or neurologist. MRIs, EMG/NCV and physical exam are most commonly used to help confirm the diagnosis.
Picture from www.familydoctor.org