The influence of temperature on nerve conduction in patients with chronic axonal polyneuropathy

Objectives: To determine whether the increase in conduction velocity with t emperature (Delta v/Delta T) is decreased in axonal polyneuropathy and to c ompare methods to account for low limb temperature in electroneurography. Methods: Median nerve motor and sensory conduction and tibial nerve motor c onduction were measured in 19 patients with chronic idiopathic axonal polyn europathy at baseline temperature, after warming at 37 degrees C, and after cooling at 25 degrees C. Delta v/Delta T was determined, using the skin te mperature difference and the presumed nerve temperature difference of 12 de grees C. The baseline conduction velocity was corrected for 37 degrees C, u sing mean Delta v/Delta T values for normal subjects taken from the literat ure. Results: Delta v/Delta T was positively correlated with the conduction velo city after warming at 37 degrees C: the lower the conduction velocity, the lower the Delta v/Delta T. In nerves with a slow conduction velocity, Delta v/Delta T was often zero. As slower conducting nerve fibers have smaller D elta v/Delta T values, the decreased Delta v/Delta T values in our study ar e probably related to loss of fast conducting fibers. The corrected conduct ion velocity was usually faster and considerably less often abnormal than t he conduction velocity after warming at 37 degrees C. The latter can be con sidered the gold standard. Conclusion: Delta v/Delta T may be reduced in axonal polyneuropathy. The co rrection method is, therefore, not suitable to account for low limb tempera ture, as the conduction velocity is overestimated. (C) 1999 Elsevier Scienc e Ireland Ltd. All rights reserved.