[The efficacy of neurophysiological examination in the diagnosis of carpal tunnel syndrome].

INTRODUCTION

The validity of studies of nerve conduction in the diagnosis of carpal tunnel syndrome has been sufficiently demonstrated, especially the speed of nerve conduction across the carpus. It has also been proved that the result of the test varies according to its use.

OBJECTIVE

This study is to evaluate the result of the study of nerve conduction in the diagnosis of carpal tunnel syndrome in a population attending a clinical neurophysiology department for examination of suspected neuro-muscular disorders of the upper limit.

PATIENTS AND

METHODS

We selected the cut-off points of the values of speed of nerve conduction along the median nerve from the thumb (E1) and palm of the hand (E2). Those showing the best sensitivity and specificity were chosen (53 and 51 m/s respectively). We assessed the pre-test and post-test probability to measure the examination result. There was little contribution from this examination to the diagnosis of carpal tunnel syndrome in this population.

CONCLUSIONS

The high pre-test probability of a disorder is a cause of low efficacy of the examination done to confirm this and the opposite occurs when it is done to rule it out. The efficacy of an examination should be measured in the setting in which it is used since this does not depend only on its intrinsic characteristics but also on how it is used.