Magnetic resonance (MR) imaging findings in three patients with acute
onset of neuritic shoulder pain and weakness included high signal inte
nsity in supra- and infraspinatus muscles (n=2), partial involvement o
f infraspinatus muscle (n=1) and of deltoid muscle (n=1), and atrophy
of supra- and infraspinatus muscles (n=2). Clinical diagnosis of acute
brachial neuritis (Parsonage-Turner syndrome) correlated with MR imag
ing results in all cases.