Entrapment of the Suprascapular Nerve
Suprascapular nerve entrapment is a condition that occurs in a variety of different patients with many potential causes of the condition.
Nerve entrapment can lead to Suprascapular nerve palsy resulting in shoulder weakness and possible shoulder pain. The most common clinical presentation is dull, nonspecific shoulder pain and sometimes weakness, although many times the condition is not recognized until significant shoulder muscle weakness is present or the patient fails rotator cuff rehab. It is often confused for a rotator cuff tear.
The Suprascapular nerve originates from the superior trunk of the brachial plexus and mainly from cervical nerve five and six. The Suprascapular nerve gives both motor and sensory innervation but has no cutaneous sensory innervations. Its motor innervations are to the Supraspinatus and Infraspinatus muscles of the rotator cuff. The nerve passes deep to the trapezius muscle and suprascapular notch.
The Suprascapular nerve maybe injured by a variety of different traumas or conditions. The recovery prognosis is related to the extent of the trauma and the duration of the condition. The nerve may be injured with clavicle and scapula fractures. Shoulder dislocations are also implicated as a cause of nerve injury. Labral tears with associated paralabral cyst may cause nerve entrapment with a possible dramatic resolution of weakness with surgical decompression of the cyst. Certain anatomic variations may also be the cause such as a narrow V shaped suprascapular notch. The condition is also seen as a result of a post viral syndrome and possibly from viral vaccinations.
Those individuals most commonly affected usually perform repetitive overhead activities. Classically, they are throwing athletes such as pitchers or tennis players. Swimmers also may present with this condition. I have seen this condition in a backpacker from external compression from the pack frame.
The clinical presentation is classically pain if a post viral syndrome is associated with it or more commonly weakness of the Infraspinatus and Supraspinatus muscles of the rotator cuff. Frequently, significant muscle wasting is associated with it due to a delay in diagnosis or a failure of rehabilitation. Biomechanical abnormalities from muscle weakness such as shoulder impingement syndrome or shoulder instability may be present.
The diagnosis is made from a good clinical exam individually testing the strength of shoulder girdle muscles. MRI is indicated to rule out soft tissue mass such as paralabral cyst or tumor. EMG is also indicated to help differentiate from other nerve related conditions and to help localize the site and cause of the nerve entrapment.
The mainstay of treatment is identification of the cause and cessation of offending activities. Rest and prolonged physical therapy are usually successful but may take months before muscle strength is restored. Pharmacologic treatment with prednisone, NSAIDs, and Gabapentin have also been found to be effective in some cases. In cases where physical compression is present and conservative measures fail, then a variety of surgical decompression procedures may be indicated.
Suprascapular nerve entrapment must be considered in all patients with shoulder pain or weakness.