Simultaneous Median-Radial Nerve Electrical Stimulation Revisited: An Accurate Approach to Carpal Tunnel Syndrome Diagnosis and Severity.
OBJECTIVE
To assess the accuracy of an unusual test for CTS investigation and correlate it with clinical symptoms.


METHODS
Initially, we applied a visual analog scale for CTS discomfort (CTS-VAS) and performed a standard electrophysiologic test for CTS diagnosis (median-ulnar velocity comparison). Posteriorly, a blinded neurophysiologist performed the orthodromic simultaneous median-radial nerve stimulation (SMRS) at the thumb, with recording of both action potentials over the lateral aspect of the wrist.


RESULTS
All hands (106) showed median-radial action potential splitting using the SMRS technique, in which was possible to measure the interpeak latencies (IPLs) between action potentials. The IPL and median nerve conduction velocity were different according to CTS intensity (Bonferroni; P < 0.001). There was significant correlation between IPL and median nerve conduction velocity (Spearman; r = -0.51; P < 0.01). In the same way, there was a significant correlation between IPL and median nerve conduction velocity with CTS-VAS (r = 0.6 and r = -0.3, respectively). The duration and unpleasantness of the SMRS procedure were lower when compared with standard approach (t Student < 0.001 for both comparisons). Twenty-nine symptomatic patients (39 hands) who did not fulfill criteria for CTS based on standard approach showed abnormal IPLs.


CONCLUSIONS
The SMRS technique is a simple, sensitive, and tolerable approach for CTS diagnosis. Apart from that, the data from SMRS correlated better with clinical impact of CTS in comparison with the standard approach. Therefore, this method might be useful as adjunct to standard electrophysiologic approaches in clinical practice.
*Neurology Department, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, Brazil; †Post-Graduation Program of Medical Sciences, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; ‡Department of Internal Medicine, School of Medicine, UFRGS, Porto Alegre, Brazil; §Serviço de Neurologia, Hospital de Moinhos de Vento de Porto Alegre, Porto Alegre, Brazil; and ‖Clinoson Medical Center, Porto Alegre, Brazil.
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Rodrigues
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Schestatsky
D000328:Adult; D000368:Aged; D002349:Carpal Tunnel Syndrome / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D011826:Radial Nerve / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012720:Severity of Illness Index; D013223:Statistics as Topic