Pre-Plexal Extension of Parsonage-Turner Syndrome With Nerve Root Involvement on Needle Electromyography.

Parsonage-Turner syndrome (PTS) is an inflammatory, immune-mediated neurogenic condition characterized by acute-onset, severe unilateral shoulder/upper arm pain followed by patchy weakness and atrophy. Often described as an idiopathic brachial plexitis, most cases of PTS involve the brachial plexus or its terminal branches, and root-level or paraspinal muscle involvement is rare. Among the differential diagnoses for proximal neuropathic root involvement, cervical radiculopathy by mechanical compression of the exiting nerve roots and diabetic cervical radiculoplexus neuropathy by way of immune-mediated microvasculitis, ischemic injury, and subsequent ischemic axonal damage should be considered. The latter also shares similar symptomatology to PTS with progression with subacute, painful, asymmetric involvement of the upper limb followed by atrophy and weakness of the limb. Here, we present a case of PTS with notable findings of cervical paraspinal muscle involvement on needle electromyography, highlighting a rare proximal, pre-plexal extension of this idiopathic inflammatory immune process.