Electrodiagnostic Alteration to Temperature Effect in Demyelinating Peripheral Neuropathy

ABSTRACT

OBJECTIVE: The purpose of this study was to determine the difference of temperature effects on the nerve conduction variables and to obtain correction factors for temperature in demyelinated and normal peripheral nerves. METHOD: The compound muscle action potentials (CMAPs) were recorded with wrist stimulation during cooling and warming in 10 control subjects and 13 subjects with demyelinating neuropathies. The temperature of cooling and warming were 18degrees C and 40degrees C, respectively. The time of cooling and warming were 60 minutes and composed of successive 4 sessions of 15 minutes. The skin temperature of thenar area, latency, amplitude, duration, and area of CMAPs were measured before and after each session of 15 minutes of cooling or warming. RESULTS: The time constants of parameters of CMAPs were of higher tendency in cooling than in warming. The time constants of latency of CMAP were higher in subjects with demyelinating neuropathy than in controls (p<0.05) 33.3+/-4.0 minutes versus 27.2+/-2.2 minutes in cooling; 30.0+/-7.8 minutes versus 19.6+/-3.3 minutes in warming. The temperature correction factor of latency of CMAPs was 0.23+/-0.03 msec/degrees C in control and 0.33+/-0.06 msec/degrees C in subjects with demyelinating neuropathies (p<0.05). CONCLUSION: When studying a subject with demyelinating neuropathies, we should warm the extremity for more sufficient time than in normal subject, or may applicate a differenct temperature correction factors.