Needle and surface electrode somatosensory evoked potential normative data: A comparison

Subdermal needle electrodes are now used routinely to record cortical somatosensory evoked potentials (SEPs). Investigators may make assumptions that: (1) SEP normative data obtained with surface electrodes can be used to interpret needle recordings, and (2) there is an increased potential for local dermal infection with needle electrodes. This investigation compared the waveform parameters obtained with surface and needle electrodes after stimulation of the tibial nerve, sural nerve, and L5 dermatome in 20 subjects. No statistically significant difference was found in the P latency, N latency, or P N amplitude of the needle recordings as compared to the surface recordings. Additionally, 20 subjects studied for one week after four hours of needle insertion did not show any evidence of dermal infection. This study objectively documents no statistically significant difference between needle and surface SEP recordings and substantiates the use of surface normative data for needle SEP investigations.