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 stimulus intensity for studying the dipole moment in somatosensory evoked fields. METHODS: In 17 patients (20 hemispheres), the authors studied the relationship between the dipole moment and stimulus intensity, which was quantified using the threshold of thenar muscle twitch (TMT). The dipole moment was measured at 1.0, 1.5 and 2.0 TMT. Two measurements were obtained at 1.5 TMT to determine the procedure's margin of error. RESULTS: There was no significant difference between the dipole moments measured at 1.5 and 2.0 TMT. CONCLUSIONS: Setting the stimulus intensity at 1.5 TMT or more ensures a consistent response.