MS Diagnosis Aided by McArdle’s Sign

Testing for McArdle’s sign—a rapidly reversible motor weakness brought about by head flexion in patients with multiple sclerosis (MS)—may aid in MS diagnosis in some cases, according to new findings.

Researchers arrived at this conclusion following a study of 76 patients with detectable finger extensor weakness, 52 with MS, 24 with other myelopathies, 5 with peripheral nerve lesions (PNL), and 25 healthy controls.
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McArdle’s sign was assessed through measurement of changes in finger extensor strength in consecutive trials of neck extension and flexion, first clinically (rating of 0 to 3) and subsequently with a torque measurement cell.

Results showed that the median clinical McArdle’s sign was 1 in MS patients, 0 in other myelopathies, 1 in healthy controls, and 0 in all PNL.

For head flexion, a 17% isoinertial strength reduction was observed in MS patients compared with 1% in other myelopathies, 1% in healthy controls, and -3% in PNL.

Using the test, the researchers found a 10% decrease in strength with flexion, which was 100% specific and 63% sensitive, for MS compared with other myelopathies. They also observed an 8% decrease in strength with flexion for MS compared with healthy controls (specificity: 100%; sensitivity: 65%).

Ultimately, qualitative McArdle’s sign was found to correlate with clinical McArdle’s sign. Furthermore, McArdle’s sign was found to correlate with the Expanded Disability Status Scale and pyramidal score in MS patients, but only for some patients in early phases of MS with minor disability.

“[McArdle’s sign] is a specific and moderately sensitive test for diagnosis of MS and may supplement diagnosis in certain clinical situations,” the researchers concluded. “Clinical examination is moderately reliable in detecting this sign.”

These findings were presented at the 2018 American Academy of Neurology Annual Meeting in Los Angeles, California.

—Christina Vogt

Reference:

Weinshenker B, Savoldi F, Nasr Z et al. McArdle’s sign: a specific sign of multiple sclerosis. Paper presented at: 2018 AAN Annual Meeting; April 21-27, 2018. Los Angeles, CA.

https://submissions.mirasmart.com/Verify/AAN2018/submission/temp/rad0E584.pdf

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