(Kiosk 2) Paralabral Cyst as a Rare Cause of Brachial Plexopathy: A Case Report

Case Diagnosis: A swimmer with a paralabral cyst.

Case Description or Program Description: A 27-year-old swimmer presented with right anterior shoulder pain, weakness, numbness, burning, and paresthesias radiating down the anterior upper arm and medial forearm into the fourth and fifth digits. Pain was exacerbated by shoulder extension and abduction with difficulty engaging periscapular muscles while swimming. Physical exam revealed atrophy of the infraspinatus and 4/5 strength in the right upper extremity key muscles. History included a similar presentation one year ago which improved after cyst aspiration.

Setting: Outpatient Musculoskeletal Clinic

Assessment/Results: Diagnostic ultrasound revealed a 3.2 x 2 x 1.9 cm well-circumscribed mass in the spinoglenoid notch. Aspiration yielded 2 mL of viscous, serous fluid resulting in complete resolution of symptoms and improved functional strength. Electrodiagnostic study was unremarkable.

Discussion (relevance): Paralabral cysts are pockets of joint fluid that are commonly caused by labral tears, and found outside of the glenohumeral cavity. Their location can impinge the suprascapular nerve as it runs through the spinoglenoid notch to innervate the infraspinatus. Compression here by the cyst causes isolated weakness of the infraspinatus with posterior shoulder pain. Due to the cyst location, other neural structures are unlikely to be compromised. Our patient’s distribution of symptoms were more consistent with a global plexopathy involving multiple roots or trunks. Considering symptom relief after cyst aspiration on multiple occasions, and a negative EMG, plexus compromise or nerve root impingement is unlikely. Pain relief with decompression of the suprascapular nerve in the spinoglenoid notch confirmed the atypical presentation of suprascapular neuropathy. To our knowledge, this is the first reported case of diffuse plexopathy-like presentation secondary to a paralabral cyst.

Conclusions: Although paralabral cysts of the shoulder usually result in isolated infraspinatus weakness and posterior shoulder pain due to suprascapular nerve compression, clinicians should be aware of atypical presentations such as global plexopathy in this case.