Cases Questions

A. Incorrect. Parsonage-Turner syndrome (also known as acute brachial neuritis) is an idiopathic denervation of the shoulder muscles resulting in pain and weakness. The muscles demonstrate high SI on T2-weighted imaging due to acute denervation edema and ultimately atrophy and fatty replacement. The suprascapular nerve and, therefore, the supraspinatus and infraspinatus musculature are typically involved. Axillary nerve involvement may occur but is less frequent.
B. Incorrect. While chronic tears of the rotator cuff tendons may be associated with muscle atrophy and fatty replacement, no tears are demonstrated in the test case.
C. Correct. Quadrilateral space syndrome is caused by compression of the axillary nerve in the quadrilateral space, usually by small fibrous bands or ganglion cysts and clinically manifests as mild shoulder pain. Axillary nerve dysfunction may eventually lead to atrophy of the teres minor and deltoid musculature.
D. Incorrect. The teres minor and deltoid muscles are supplied by the axillary nerve, not the suprascapular nerve. The suprascapular nerve innervates the supraspinatus and infraspinatus muscles, which appear normal.

Kaplan, Helms, Dussault, Anderson, Major. Musculoskeletal MRI. WB Saunders Co., Philadelphia, PA. 2001

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