MRI Diagnosis and Follow-up of a Paraglenoid Cyst Treated by Percutaneous Aspiration: A Case Report.

Introduction

The differential diagnosis of shoulder pain and dysfunction commonly includes rotator cuff impingement and tendinopathy, adhesive capsulitis, glenohumeral instability, degenerative joint disease, and cervical neuropathy. Less common causes include scapulothoracic disorders, Pancoast tumor, peripheral neuropathy and suprascapular nerve entrapment. The diagnosis of suprascapular nerve entrapment may be delayed because the symptoms associated with the disorder, insidious onset of supraspinatus and infraspinatus muscle weakness accompanied by deep posterior pain, are nonspecific. Suprascapular nerve compression can occur anteriorly and superiorly at the suprascapular notch or posteriorly and inferiorly at the spinoglenoid notch. (1,2) Suprascapular nerve impairment may result from a scapular fracture, overuse traction syndrome, or a space-occupying lesion such as a cyst, solid tumor, hematoma, or ligamentous hypertrophy. (3,4,5) In this case report, a spinoglenoid notch cyst, treated successfully with percutaneous aspiration, is presented.

Case Report

A 51 year-old, right-hand dominant female presented with a six week history of pain and functional impairment involving her right shoulder. She reported a past history of right shoulder bursitis and intermittent stiffness of the shoulder following exercise. Approximately, six weeks prior to presentation, she over-stretched her arm and experienced severe pain. Application of a heating pad and administration of NSAIDs provided partial relief of symptoms. At presentation, she reported right shoulder pain with motion, night pain, and intermittent paresthesias involving the right upper extremity. Physical examination of her right shoulder revealed the presence of tenderness over the rotator cuff, long head of the biceps tendon, and coracoid process but no tenderness over the suprascapular notch and no evidence of muscle atrophy. She accomplished 160-170 degrees of forward flexion and abduction with marginal impingement signs. Slight weakness of the supraspinatus muscle was noted with no appreciable weakness involving the infraspinatus or subscapularis muscles. Biceps provocative tests were negative.

Radiographs of the right shoulder revealed hypertrophic arthropathy of the acromioclavicular joint, ossification of the coracoacromial ligament, and cystic reaction of the greater tuberosity. An MRI scan revealed the presence of a full-thickness tear of the supraspinatus tendon and a cystic lesion involving the spinoglenoid notch. (Figure 1) EMG and nerve conduction studies suggested suprascapular nerve entrapment.

The patient underwent CT-guided percutaneous aspiration of the cyst and local steroid injection. Cytologic evaluation of the cyst contents revealed the presence of macrophages and synovial cells. On an MRI examination performed approximately 7 months following the cyst aspiration, a much smaller spinoglenoid notch fluid collection was identified. (Figure 2) An MRI study performed approximately 28 months following the procedure revealed further reduction in the size of the cyst. (Figure 3) On follow-up clinical evaluation, no demonstrable rotator cuff weakness or atrophy was noted.

Discussion

Cystic lesion involving the spinoglenoid notch include ganglion and synovial cysts, cysts related to dissection of synovial fluid through a glenoid labral tear into the periarticular soft tissue, and cystic collections associated with delaminating rotator cuff tears. (3,6,7) Synovial cysts arise from the joint capsule or the synovial lining of an adjacent bursa. Ganglion cysts, typically containing a mucinous internal matrix, may be associated with an adjacent joint, bursa, ligament, or tendon. Extension of synovial fluid through a labral tear or rotator cuff tear into non-bursal periarticular soft tissue represents a more complex etiology as cyst formation occurs secondary to primary chondral or tendinous pathology.(3,7) The presence of a concomitant labral or rotator cuff tendon defect complicates treatment in that excision or drainage of the cyst may prove only transiently successful in alleviating nerve compression. If the pathway for synvoial fluid to enter the spinoglenoid notch remains patent, the cyst may recur.(3,6)

Non-operative approaches to the treatment of suprascapular neuropathy include rest and activity modification, physical therapy, and the administration of NSAIDs. Operative approaches include percutaneous cyst aspiration and arthroscopic or open decompression of the cyst with arthroscopic or open repair of a labral tear or rotator cuff tear, if present.(1,6)

In this case, percutaneous aspiration of the cystic lesion alone was successful in relieving suprascapular nerve impairment without cyst recurrence during a follow-up period exceeding 2 years. The cyst may have represented a noncommunicating synovial cyst or a periarticular cyst that no longer communicated with the shoulder joint through a rotator cuff tear or labral tear because the pathway spontaneously sealed due to fibrosis or reactive synovial proliferation. Percutaneous aspiration of a spinoglenoid notch cyst in a patient with suprascapular nerve impairment represents a reasonable initial, less invasive approach to treatment that may adequately alleviate the patient’s symptoms, particularly if communication between the cyst and the shoulder joint is not demonstrated on direct or indirect MR arthrography. However, if the cystic lesion recurs, an arthroscopic or open surgical procedure may be required to excise or drain the cyst and address the rotator cuff tear or labral tear that relates to the primary etiology of the spinoglenoid cyst.

References

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