Suprascapular neuropathy due to a spinoglenoid notch ganglion mimicking a rotator cuff tear

Clinical History

A 5-month history of left shoulder pain. There was no obvious precipitating factor and the only abnormality on physical examination was an element of painful arc.

Imaging Findings

The patient presented with a 5-month history of significant pain and weakness in the left shoulder with no obvious precipitating event. On examination there was no muscle wasting, an element of painful arc with weakness of supra and infraspinatus and normal power in the subscapularis muscle.

No abnormality was seen on plain radiography. Magnetic resonance arthrography (MRA) demonstrated a well-defined 1.5cm x 2cm ovoid lesion located in the spinoglenoid notch, projecting towards the suprascapular notch. It exhibited three signal characteristics: (1) an area with low signal on T1-weighted images, and high signal on T2-weighted images, in keeping with fluid; (2) high signal on T1-weighted, STIR and fat saturated images after contrast medium injection, implying a communication with the joint, and (3) an area, located anteriorly, showing low signal on T1- and T2-weighted images, probably indicating a gas collection (Figs 1,2).

There was also a tear of the posterior glenoid labrum outlined by contrast medium and a small SLAP lesion. The rotator cuff was intact. On a subsequent CT examination the area of low signal was seen to move between the supine and prone positions, confirming a gas collection (Fig. 3).

Discussion

The suprascapular nerve arises from the brachial plexus (roots C4, C5 and C6) and passes through the scapular notch beneath the transverse scapular ligament, dividing into a branch which supplies the supraspinatus muscle and one that passes through the spinoglenoid notch to supply the infraspinatus muscle. Depending on location trauma, anomalies of the notch, a hypertrophic transverse scapular ligament, a ganglion cyst or other SOL can result in a neuropathy affecting either only the infraspinatus or both the infra and supraspinatus muscles [1]. Sporting activities involving overhead motion such as tennis, swimming, weight lifting and volleyball can lead to traction injuries [2,3].

There are several theories regarding the pathogenesis of ganglion cysts, including myxoid degeneration of the joint capsule, joint fluid leaking through a weak capsular area and tears in the labrum (hip and shoulder). Shoulder ganglion cysts have been associated with gleno-humeral intra-articular pathology, namely a posterior capsulolabral tear [4] (as seen in this patient). The presence of gas and contrast medium within the ganglion in this case supports a theory of communication between the joint and ganglion cyst.

Gas-containing ganglia have rarely been reported [5]; to our knowledge this is the first concerning a shoulder ganglion. Gas may be seen radiographically in a number of situations. Its presence is normal in the vacuum phenomenon when a joint is subjected to traction by distracting apposing joint surfaces. Intra-articular gas is also present in established degenerative conditions of the spine and peripheral articulations. Serial CT studies may show the cyst filling alternately with gas and fluid.

Differential Diagnosis List

Final Diagnosis

Communicating spinoglenoid ganglion

URL:	https://www.eurorad.org/case/1789
DOI:	10.1594/EURORAD/CASE.1789
ISSN:	1563-4086