Determining the appropriate stimulus intensity for studying the dipole moment in somatosensory evoked fields: a preliminary study

Objective: To establish a simple method of determining the appropriate stim ulus intensity for studying the dipole moment in somatosensory evoked field s. Methods: In 17 patients (20 hemispheres), the authors studied the relations hip between the dipole moment and stimulus intensity, which was quantified using the threshold of thenar muscle twitch (TMT). The dipole moment was me asured at 1.0, 1.5 and 2.0 TMT. Two measurements were obtained at 1.5 TMT t o determine the procedure's margin of error. Results: There was no significant difference between the dipole moments mea sured at 1.5 and 2.0 TMT. Conclusions: Setting the stimulus intensity at 1.5 TMT or more ensures a co nsistent response. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.