Influence of temperature on comparative nerve conduction techniques for carpal tunnel syndrome diagnosis.

In this study we compared the effect of temperature variation (> or = 32 degrees C to < or = 27 degrees C) on latency differences median to ulnar (ringdiff), median to radial (thumbdiff), palmar median to ulnar (palmdiff) and the sum of three, the combined sensory index (CSI), in 15 controls and 12 patients with carpal tunnel syndrome (CTS). After cooling, ringdiff was the most reliable technique with little variation in both controls and patients; thumbdiff decreased dramatically in controls and could even come within normal limits in patients; palmdiff increased only in patients; CSI decreased significantly in controls and showed a slight increase in patients with no loss in electrodiagnosis accuracy. The high increase of palmdiff in patients, and the high decrease of thumbdiff in controls, after cooling, could not be explained only for fiber size in the nerve trunks. We concluded that for CTS electrodiagnosis even latency differences in same person/same limb could be significantly modified after cooling not previously emphasized in literature.