The study is designed to quantitate McArdle's sign, an increase in measurable weakness with neck flexion described in patients with multiple sclerosis, and to determine whether it is or is not specific for multiple sclerosis.

Finger strength will be measure using a torque-measuring device designed to quantitate finger extension strength. The device was designed for point of treatment use, patient safety and portability. Strength will be measured in 5 paired trials, first with neck extended and then with neck flexed. Two protocols will be evaluated, one testing isometric strength against a fixed resistance and the second testing strength against dynamic resistance. McArdle's sign is the difference between strength with neck extension and strength with neck flexion.

The data will be digitally registered and dynamic neck position will be recorded electronically in real time. Graphs of dynamic changes in torque versus neck position will be generated and superimposed. Strength will be quantitated using Matlab software.

Consecutive patients with myelopathy of any cause with detectable finger extensor weakness will be studied, either due to MS or due to other cause of myelopathy (other inflammatory, vascular, compressive, neoplastic and other). Additionally, normal controls will be studied as will patients with finger extension weakness due to peripheral nerve lesions.

Inclusion Criteria:

• Myelopathy of any cause with finger extension weakness
• Patients with peripheral neuropathy with finger extension weakness
• Healthy controls

Exclusion Criteria:

• Pregnant subjects.

Patients with myelopathy of any cause and peripheral neuropathy who have detectable finger extension weakness.