Dr. Brian Weinshenker, a neurologist at Mayo Clinic, reviews his article appearing in the August 2019 issue of Mayo Clinic Proceedings, which was able to distinguish patients with demyelinating disease with 100% specificity in 70% of patients with myelopathy who demonstrated 10% or greater increase in finger extensor weakness with neck flexion compared to extension.

Although MS is one of the most common causes of myelopathy, it is often challenging to distinguish it from other causes. Demonstration of McArdle sign, a rapidly reversible weakness induced by neck flexion, a bedside test, may greatly facilitate and increase the specificity of a diagnosis of MS as the cause of limb weakness.