451 - Parsonage-Turner Takes an Unexpected Turn: A Distal Arm Dilemma

77 year old female with hypertension, hyperlipidemia, and no recent surgical history who presented to the outpatient clinic with six months of right hand paresthesias and weakness in her thumb and index finger. On exam, there was decreased strength on wrist extension and finger abduction with normal reflexes. MRI brain, MRA neck, and MRI of the cervical spine were unremarkable. Lumbar puncture, autoimmune and rheumatologic labs, cervical x-rays and MRI of the right brachial plexus resulted as unremarkable. Electrodiagnostic studies were completed showing a pattern consistent with neurogenic amyotrophy (Parsonage-Turner Syndrome). There was evidence of a distal right median neuropathy and distal radial and ulnar neuropathy with reinnervation present. Distally innervated median, ulnar, and radial muscles had reduced recruitment with normal right proximal upper extremity muscles. Left upper extremity electrodiagnostics were normal. Patient was recommended to repeat the study in 3 months.
 

Discussions:

Parsonage-Turner Syndrome (PTS), also known as neurogenic amyotrophy, is a rare idiopathic disorder characterized typically by unilateral shoulder pain progressing to weakness and paresthesias. It is a diagnosis of exclusion. While the exact etiology and pathology of PTS is unknown, there is an association with surgical procedures and viral illness. The most common nerves affected are the suprascapular, axillary, and the long thoracic nerves. PTS is self-resolving. This patient’s presentation is atypical due to the initial presentation of numbness and distal weakness and involvement of the median, ulnar, and radial nerves. 
 

Conclusions: ^{This case showcases an atypical presentation of Parsonage-Turner involving the median, ulnar, and radial nerves. While PTS is already a diagnosis of exclusion, this rare case presentation highlights the importance of a strong clinical exam and utilization of electromyography.}