[The centimetric test: a diagnostic conformation test of very limited forms of carpal tunnel syndrome?].

In 5 to 10% of cases of carpal tunnel syndrome, the abnormalities of nerve conduction of the median nerve at the wrist remain too discrete for the diagnosis to be confirmed by classical electromyographic techniques. The centimetric test provides a very precise anatomo-functional analysis and studies nerve conduction, centimetre by centimetre, over a distance of 10 centimetres (11 recordings). The time taken by the sensory potential to travel 1 centimetre is referred to as the centimetric conduction time (CCT). The normal mean CCT is equal to 0.185 m.sec and the CCT is considered to be pathological when it is greater than twice the normal mean CCT or more greater than 0.40 m.sec on the first approximation. The use of the centimetric test in 45 cases of clinical suspicion of carpal tunnel syndrome in which classical electromyographic data were insufficient was able to confirm the diagnosis in 32 cases and exclude it in 10 cases. In 3 cases raising particular problems, the centimetric test was also very useful. The centimetric test allows an individual diagnosis in each of these cases, whereas the same conclusions could only be drawn from overall statistical analysis of the classical electromyographic data of the two populations. The centimetric test also localizes the origin of compression in these very limited forms to the lower edge of the flexor retinaculum of the carpus in more than 80% of cases.