The role of ultrasonography of the brachial plexus in differentiating between Parsonage-Turner syndrome and neuroborreliosis. A pictorial review.

Parsonage-Turner syndrome (PTS), also known as neuralgic amyotrophy (NA), is an idiopathic inflammatory neuropathy of the brachial plexus presenting with neuropathic pain and motor deficits of the shoulder girdle. Routinely, PTS must be differentiated from infectious variants of brachial plexitis, especially early manifestations of neuroborreliosis. Both conditions can quickly lead to significant disability, so early, targeted therapy based on a correct diagnosis is essential for a favourable clinical outcome. High-resolution ultrasound (HRUS) can quickly and non-invasively differentiate PTS from infectious forms of brachial plexitis by detecting nerve twisting and swelling with the so-called "hourglass-like" constriction sign. The following article presents the authors' proposal for an HRUS protocol for the brachial plexus and shows typical ultrasound findings in PTS and brachial plexitis with Banwarth's syndrome due to Borrelia infection.