Brachial Neuritis is a condition of severe shoulder pain that usually radiates down the arm and up to the neck and scapula. It can also be referred to as neuralgic amyotrophy (NA) and/or parsonage-turner syndrome. The pain is sudden, severe and may last for a few weeks. This pain may disturb sleep! It usually occurs on its own without a history of trauma. The condition occurs more in males and it may occur at any age.
The position of comfort is the shoulder adducted with the elbow flexed. Neck movement and Valsalva’s maneuver do not increase the pain. Pain is increased by movement of the arm. Although the pain is severe and sudden, lasting at least a few weeks, the condition is usually under diagnosed or not diagnosed at all.
Weakness may be absent in the acute phase, however as the pain resolves, weakness of certain muscles will remain. The degree of weakness correlates with the severity of the initial pain.
The muscles that are commonly involved are the supraspinatus and the infraspinatus muscles. The suprascapular nerve is the most commonly involved followed by the deltoid, which is the abductor of the s shoulder innervated by the axillary nerve.
The condition may occur bilaterally and may occur subclinically (only seen on an EMG). Muscle weakness may continue for a significant period of time. Sensory changes may be variable. If there is no sensory loss, this is a classic finding that confirms the diagnosis. There is a decreased sensation in a lot of cases. The lateral antebrachial cutaneous nerve is usually involved.
Motor changes predominantly occur over sensory changes and can involve the brachial plexus from C5-T1 with a variable degree of weakness. It can affect more than one nerve branch with certain patterns of involvement can be seen on the MRI.
It is a benign, self-limiting problem with 90% of patients returning to near normal condition in about 3 years. Only about 1/3 of the patients will recover at about 1 year. The etiology of brachial plexus neuritis is unknown.
Hyperintense muscles involved in the sagittal plane (supraspinatus, infraspinatus, and deltoid). In advanced cases, the muscles will either be atrophied or have fatty infiltration.
EMG and Nerve studies are helpful for the diagnosis and the prognosis. In the first 4 weeks, there will be acute denervation in the roots and the peripheral nerves. EMG may be abnormal for up to 7 years after the diagnosis.
Rule out other conditions such as radiculopathy from a herniated disc. This can be excluded from imaging of the cervical spine. Other conditions that may be considered differential diagnoses are adhesive capsulitis and lyme disease. There are two particular conditions that are very interesting with acute brachial neuritis. The first is bilateral interosseous nerve palsy, which is caused by viral brachial neuritis. The patient has the inability to do the Ok sign. It is motor loss that follows intense shoulder pain and usually the condition resolves with time.
The second condition is winging of the scapula. The serratus anterior muscle involvement may cause dull aches and pain. Acute, sudden severe pain consider with acute brachial neuritis that involves the C7 nerve root. C7 nerve root gives the long thoracic nerve, which innervates the serratus anterior muscle. If the patient has severe shoulder pain and winging of the scapular rule out brachial neuritis!
The treatment includes rest, observation and steroid injections. Avoid using a sling, a sling will cause flexion and internal rotation contracture of the shoulder. The sling may also cause a stiff elbow.