Parsonage Turner Syndrome

Parsonage-Turner syndrome (PTS), also known as acute brachial neuritis and neuralgic amyotrophy, is a rare condition that is characterized by acute onset of severe shoulder pain that is soon followed by weakness of at least one shoulder muscle. It is thought to be due to a systemic or localized infectious or immunologic process.

MRI typically demonstrates diffuse T2 hyperintensity involving one or more muscles in the distribution(s) of one or more peripheral nerves originating from the brachial plexus (see below). Atrophy of these muscles, seen on T1-weighted images, may also be present.

The suprascapular nerve (supraspinatus and infraspinatus muscles) is the most commonly affected, followed by the axillary nerve (deltoid and teres minor muscles). The subscapular nerve (subscapularis [upper and lower branches of subscapular nerve] and teres major [lower branches] muscles) is a distant third.

The right side is more commonly involved (~60% vs 30% for the left). Bilateral involvement is seen in about 10% of cases.

PTS is a self-limited condition (although resolution may take several years) that is important to be aware of because it can be clinically confused with more common disorders such as cervical spondylosis, rotator cuff tear, shoulder impingement syndrome, and acute calcific tendonitis, and may even lead to unnecessary surgery.

References

Gaskin CM and Helms CA. Parsonage-Turner Syndrome: MR Imaging Findings and Clinical Information of 27 Patients. Radiology. 2006; 240:501-507.