Which EMG and nerve conduction study findings are characteristic of ulnar neuropathy?

Updated: Jun 08, 2018
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Findings are considered to be positive for cubital tunnel syndrome when the motor conduction velocity across the elbow is less than 50 m/s or when the difference between the motor conduction velocity across the elbow and that below the elbow exceeds 10 m/s.

If the point of maximum conduction delay and drop in amplitude of the compound muscle action potential (CMAP) is at or just proximal to the medial epicondyle, compression of the ulnar nerve is probably at the level of the epicondylar groove. If the point of maximum conduction delay and drop in CMAP amplitude is 2 cm distal to the medial epicondyle, compression is probably in the cubital tunnel. Unfortunately, false-positive results are obtained in 15% of cases.


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