A promissing method of CTS investigation: Median-radial nerve action potential splitting (MRS) (P5.060)

Objective: To evaluate the accuracy of a new method of CTS investigation, compare it with a standard method and correlate with clinical symptoms. Introduction: Carpal tunnel syndrome is the most common nerve entrapment observed in clinical practice affecting the median nerve at the wrist level. There are many electrophysiological ways to diagnose, but most of them are time consuming, painful and with poor sensibility. Methods: Forty-two patients (61 hands) were assessed clinically and neurophysiologicaly. First, we applied the Boston Carpal Tunnel Syndrome Questionnaire,Visual analogical scale and performed a standard method of analysis of the median and ulnar nerve. A blinded neurophysiologist performed a novel technique (Median-radial nerve action potential splitting, or MRNS) that consists of simultaneous orthodromic electrical stimulation of the median and radial nerves at the thumb, with simultaneous recording of both action potentials at the lateral aspect of the wrist. Results: Sixteen patients (26 hands) were initially excluded because of normal nerve conduction study and/or absent potentials. All the remaining subjects (61 hands) showed slowed nerve conduction velocity (NCV) in comparison with ulnar nerve) and/or Median-radial nerve action potential splitting at the wrist. There was a negative and significant correlation between the conduction velocity (palm and finger level) and the median-radial interpeak latency (r=0.5; p<0.001). We found significant differences between the distance of median-radial peaks when patients were classified according to standard criteria for CTS intensity (light, moderate and severe). The self-perception of symptoms, measured by means of a visual analogue scale was positively correlated with the median-radial interpeak latency, but not with NCV from standard technique. Eighty per cent of patients preferred the MRNS compared to conventional approach. Conclusion: Median-radial nerve action potential splitting technique is accurate, user friendly, and less painful than the standard approach. Therefore this method is recommendable for use in clinical neurophysiology practice. Disclosure: Dr. Winckler has nothing to disclose. Dr. Rodrigues has nothing to disclose. Dr. Bandeira has nothing to disclose. Dr. Vall-Sole has nothing to disclose. Dr. Schestatsky has nothing to disclose.