Plain films if there is history of trauma
Consider MRI in the ED to rule out acute cervical spine pathology
Outpatient brachial plexus MRI or magnetic resonance neurography
Outpatient EMG - should be performed at least 3 weeks after symptom onset to show findings4
Parsonage-Turner syndrome
Idiopathic
Down syndrome
Post-infectious
Kounis syndrome
Viral
Sheehan's syndrome
Epstein-Barr, CMV, influenza, parvovirus, coxsackie, HIV, Polio