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Forearm velocity in carpal tunnel syndrome: when is slow too slow?
J E Donahue1, E M Raynor, S B Rutkove
1Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
Objective:
To correlate the frequency of superimposed processes (SPs) such as radiculopathies, polyneuropathies, and plexopathies with median motor forearm conduction velocity (MMFCV) in patients with carpal tunnel syndrome (CTS).
Design:
All cases of diagnosed CTS were retrospectively analyzed for evidence of SPs.
Setting:
Electrophysiology laboratory of a tertiary care center.
Participants:
One hundred fifty-five patients (44 men, 111 women), ages 19 to 94, who were referred for and met electrophysiologic criteria for CTS, both with and without MMFCV slowing.
Main Outcome Measure:
The frequency of SPs in patients with no, mild, moderate, and severe MMFCV slowing.
Results:
A total of 192 arms from 155 patients were studied. Of 14 arms with mild slowing (MMFCV of 47.0 to 49.9 m/sec), 2 (14%) had an SP. Of 15 arms with moderate slowing (MMFCV of 43.0 to 46.9 m/sec), 7 [corrected] (46%) had an SP. Of 9 arms with severe slowing (MMFCV of < 43.0 m/sec), 4 (44%) had an SP. The frequency of SPs for both the moderate and severe groups was significantly higher than that in patients with a normal MMFCV (p < .01); of 154 arms with a normal MMFCV, only 9 (6%) had an SP.
Conclusion:
In cases of CTS, the finding of moderate to severe slowing of MMFCV (< 47.0 m/sec) should prompt a careful electrophysiologic investigation to exclude an SP.