Electrodiagnostic Findings Compared to Patient Symptoms in Carpal Tunnel Syndrome
When diagnosing carpal tunnel syndrome (CTS) doctors rely on patient report of symptoms. Electrodiagnostic tests such as nerve conduction velocity (NCV) can also help identify problems with nerve transmission. Pressure on the nerve or nerve entrapment often changes NCV.

In this study, researchers compare patient report of symptoms against the results of electrodiagnostic tests. They expected to see a difference in scores for patients with psychologic problems. Patients who were not depressed and did not catastrophize their symptoms were expected to have more true nerve changes seen on NCV.

They found that symptoms of CTS such as pain, weakness, and numbness are separate measures from the results of electrodiagnotic tests. It's better to use both types of testing when diagnosing CTS.

Normally CTS affects small sized nerve fibers. Electrodiagnostic tests are more likely to show changes in large nerve fibers and might not show changes in the small nerve fibers. Early symptoms of CTS are usually worse in the beginning when electrodiagnostic testing isn't as likely to show any changes.

Over time, the symptoms may get better when true changes would show up on testing. But the patient feels better and testing isn't done. The authors suggest this pattern of worse-to-better might happen because the patient gets used to the pain and doesn't notice it as much. Or perhaps the symptoms just burn out and go away.

Whatever the explanation, the results of this study showed that there isn't a direct link between electrodiagnostic findings and patient symptoms and function. To get a true and accurate picture of what's going on, the physician must rely on both patient report and testing.
References
Leighton Chan, MD, MPH, et al. The Relationship Between Electrodiagnostic Findings and Patient Symptoms and Function in Carpal Tunnel Syndrome. In Archives of Physical Medicine and Rehabilitation. January 2007. Vol. 88. No. 1. Pp. 19-24.