There is a posteroinferior labral tear 6-8:00 that communicates with a large inferior paralabral cyst which courses through the Quadrilateral space where it compresses the axillary nerve.
Paralabral cyst is the most common identifiable mass to cause quadrilateral space syndrome; most often there is no identifiable mass and fibrous bands are implicated.
There is selective edema (white arrows) of the Teres Minor, suggesting compression of the posterior branch of the axillary nerve.
The muscle is compressed, but you can see acute neuropathic edema without atrophy.
We often see neuropathic atrophy / edema of the T Minor +/- the deltoid…but I don’t recall a clinical history of neuropathic pain…I think it is more often an incidental MRI finding (correct me if I am wrong)
The Obl Ax images show the cyst and the denervation edema. The scan plane indicated in the Sag image also shows the posteroinferior labral tear
Basic anatomy from Orthobullets
(the Triangular Interval contains the radial nerve and profunda brachii artery and the Triangular Space contains the scapular circumflex artery)
If you have a companion case, feel free to share it with the group
Hilary
