Periarticular Cysts and Suprascapular Nerve Compression

Literature Review

Surgeons agree that labral tears can result in cyst formation. The proposed cause is similar to wrist ganglia. It is postulated that a labral tear allows joint fluid to leak and form an extra-articular accumulation. Communication between the glenohumeral joint and the cyst has been demonstrated, but there is no evidence for this proposed cause. Iannotti described his approach to cyst treatment, which consists of arthroscopic cyst decompression and labrum repair to treat patients with suprascapular neuropathy.

Diagnosis

Patients present with shoulder pain, weakness, or both. These nonspecific symptoms do not point the examiner toward the diagnosis of a periarticular cyst. The surgeon should be suspicious when the findings are at odds with the typical presentation of patients with rotator cuff impingement or glenohumeral instability—for example, a patient younger than 40 years who presents with rotator cuff symptoms without any significant trauma or any history of repetitive shoulder activity. Symptoms from a periarticular cyst may mimic rotator cuff pathology, labral pathology, suprascapular nerve compression, or some combination. Labral detachment may mimic rotator cuff symptoms as a result of contact against the posterior-superior glenoid, and the patient may complain of posterior-superior shoulder pain while throwing or performing other activities that require the arm to be placed in abduction and external rotation.

Mechanical labral symptoms include sensations of locking, catching, or popping. Pressure from the cyst on the suprascapular nerve can cause pain or a burning discomfort in the scapular or trapezius muscle region ( Fig. 8.4 ).

Nerve compression can also result in weakness. This weakness may be difficult to detect because, over time, compensatory hypertrophy can develop in the teres minor muscle ( Fig. 8.5 ).

However, in many cases, the infraspinatus by itself or both the supraspinatus and infraspinatus can be moderately atrophied, and there can be moderate weakness on examination ( Fig. 8.6 ). When patients are tested against overhead resistance, the weakened rotator cuff does not adequately stabilize the humeral head, and slight superior subluxation occurs. This results in complaints very similar to those complaints accompanying subacromial impingement.

No specific symptoms are diagnostic of a cyst, but some of these complaints, in combination with the physical exam findings, will often prompt the physician to order an MRI. The most common site of periarticular or paralabral cysts is in the posterior-superior shoulder. There may be associated rotator cuff findings, such as a partial-thickness rotator cuff tear, but more commonly, there is a posterior superior labral tear. The size can be variable but is typically 1 to 2 cm in diameter. The communication with the labral tear may or may not be apparent. The surgeon should also be aware that the cyst may not be producing any symptoms at all and may be an incidental finding.

Nonoperative Treatment

Conservative management of a labral tear with an associated cyst includes selective rest, activity modification, nonsteroidal anti-inflammatory medication, or aspiration and injection. If there is weakness, it can be managed with a strengthening program. However, often—as long as the labral tear and cyst persist—symptoms will continue. Aspiration with or without steroid injection has been shown to give short- to medium-term relief, but it needs to be done with image guidance ( Figs. 8.7–8.10 ).