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More often than not, paralabral cysts of the shoulder are an infrequent finding on MRI or MR Arthrogram.  However, it is a significant diagnosis as they may cause a compression neuropathy of the suprascapular or axillary nerves depending on where they occur, along with a variety of other symptoms.  About 2-4% of the general population is likely to have it and presentation may be common in males (especially around the third to fourth decades).  On average, this cyst measures 10–20 mm in diameter and are located mainly on the posterosuperior aspect of the glenoid.  These cysts may represent a synovial cyst, ganglion cyst or pseudocyst.  The person with paralabral cyst has an increased risk of having glenoid labral tears

What are paralabral cysts?

Paralabral cysts are swellings that develop around the socket of the shoulder joint.  Direct communication between a cyst and joint is not commonly seen.  A paralabral cyst is termed when a focal well-defined collection of fluid is seen outside the joint under tears of the labrum.  They can occur anywhere around the joint and can be unilocular (single-chambered) or multilocular (having many compartments or cavities).  Paralabral cysts as such may not give rise to pain but the presence of labral tears accompanied with the cysts give rise to pain.  These cysts may become large and impinge some of the important nerves around the shoulder.  As a result of this, pain coupled with weakness of the muscles supplied by the nerves is a common symptom.  The commonest nerve affected is the suprascapular nerve.  The suprascapular nerve can be compressed at the spinoglenoid notch or at the suprascapular notch, leading to suprascapular nerve palsy.  Paralabral cysts are generally noted along the posterior, superior, and anterior aspects of the glenohumeral joint.  Ironically, they are unlikely to be in the inferior part of the joint.  These cysts are rarely to be diagnosed clinically unless they cause compression of the surrounding structures, like nerve.

Diagnosis of paralabral cyst:

Patients suffering from paralabral cyst have chronic shoulder pain as the chief complaint.  It requires an MRI or MR Arthrogram to find out if it is as a consequence of a paralabral cyst.  In the absence of nerve compression symptoms it is a tad difficult to zero in on the diagnosis unless there is an image that supports the diagnosis.  Knowledge of the clinical condition and its imagine features is critical for a correct diagnosis of this unusual cause of chronic shoulder pain.

In most of the cases paralabral cysts are noted around the shoulder girdle.  These cysts are believed to develop when a labral or a capsular tear allows synovial fluid to be forced into the tissues, creating a one-way-valve effect.  Orthopaedic literature reveals that paralabral cysts of the shoulder mostly present with symptoms of entrapment or compression of the nerve.  In the absence of nerve entrapment or compression symptoms, paralabral cysts of the shoulder are not often considered when a patient presents with chronic shoulder pain.

Despite an improved recognition of paralabral cysts, however, the diagnosis of these lesions remains elusive.  What makes the diagnosis challenging is the unspecific history as well as the presence of potentially confusing conditions such as rotator cuff disease, SLAP lesions, impingement syndrome and occult instability.  Conservatively, shoulder pain in the glenoid labral area is attributed to SLAP lesions and compression of nerve.  Generally when a patient presents with chronic shoulder pain, the first-line of treatment that a shoulder specialist recommends is rest and activity modification.  The possibility of paralabral cysts is commonly considered after weighing the chances of osteoarthritis, rheumatoid arthritis, osteomyelitis, malignant neoplasms or benign bone lesions.

The exact origin and development of paralabral cysts are not well known, nor is the infective agent that causes paralabral cysts.  It is believed that trauma results in tearing of the capsulo-labral complex causes these cysts to develop.  In some cases paralabral cysts can be an indicator of labrocapsular injury and instability, so effort should be taken for a careful history and a thorough physical examination to detect instability.  Patients with pralabral cysts are likely to have chronic pain even at rest.

Treatment of paralabral cysts:

Treatment of the condition is dependent upon the extent of pain and loss of function.  If the patient does not have pain, shoulder rehabilitation to maximize function is the only treatment modality that is required.  However, if the pain is present with impairment of shoulder function surgery is required.  Treatment for paralabral cysts causing nerve compression involves arthroscopic repair of the labral tear, as well as decompression of the nerve and drainage of the cyst.  Labral repair has been reported to reduce the frequency of paralabral cysts coupled with improvement in pain and shoulder function.

Conclusion:

To conclude, it is imperative for shoulder specialists to maintain an index of suspicion for paralabral cyst with labral tear in patients present with chronic shoulder pain that is refractory to other treatment modalities.  Timely recognition and treatment of these lesions can lead to a successful clinical outcome and avoid the potential danger of missed chronic lesions.

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