LARGE ELECTRODES IMPROVE NERVE-CONDUCTION REPEATABILITY IN CONTROLS AS WELL AS IN PATIENTS WITH DIABETIC NEUROPATHY

Recording site is an important cause of variability of compound muscle action potential (CMAP) and conduction parameters, which can be reduc ed by using large electrodes. Repeatability of CMAP and conduction par ameters of conventional and large electrodes was compared in 16 contro ls and 17 diabetic neuropathic patients, using defined recording sites linked to anatomical landmarks. Right-sided median, peroneal, and tib ial nerves were investigated twice with a 1-2 week interval by the sam e examiner, Compared to previous studies, conventional electrodes on s trictly defined recording sites resulted in better repeatability: intr aindividual coefficients of variation (CV) varied between 4% and 14.4% for all parameters. CV of conduction parameters, not published previo usly, was smaller than CV of CMAP parameters, The use of large electro des improved repeatability further: large electrodes resulted in subst antially smaller CV for duration, amplitude, area, and changes of ampl itude and area over a length of nerve, which were reduced by 10%, 31%, 29%, 27%, and 16%, respectively. Patients had higher CV than controls ; large electrodes reduced patient CV more than control CV, resulting in less contrast between groups, Strictly defined recording sites and large electrodes improve repeatability of motor conduction studies to relevant degrees: all CMAP and conduction parameters are suitable for longitudinal studies of neuropathic patients. (C) 1996 John Wiley & So ns, Inc.