Appearances in this case are highly suggestive of Parsonage-Turner syndrome, as there is no compression of the suprascapular nerve by a cyst or a mass.

Parsonage-Turner syndrome is an acute idiopathic brachial neuritis. Males are affected more than females. Two-thirds of cases are unilateral.

The suprascapular nerve is involved in almost all cases. The supraspinatus and infraspinatus muscles are commonly involved, followed by the deltoid muscle.

The affected muscles look initially normal. After few weeks, edema due to denervation develops in the involved muscles and gradual loss of muscle volume and fatty infiltration take place.

The disease is self-limiting and treatment is conservative.