Effect of local anesthesia on trigeminal somatosensory-evoked magnetic fields

For objective neurophysiological evaluation of the function of the trigeminal system,magnetoencephalography- based tsef (trigeminal somatosensory-evoked field) assessment would be valuable in providing spatial and temporal profiles of cortical responses. however,this necessitates knowledge of how tsef varies with trigeminal nerve dysfunctions. we introduced a conduction block of the trigeminal nerve using local anesthesia (lidocaine) to temporally mimic nerve dysfunctions,and monitored tsef changes. following an electrical stimulation of the lower lip,a magnetic response with peak latency of approximately 20 ms was identified in all participants. dipole for the peak was estimated on the post-central gyrus in the participant's own magnetic resonance image. after normalization to montreal neurological institute (mni) space and inter-participant data integration,the summary equivalent current dipole localization among participants remained in the post-central gyrus,suggesting validity of the use of mni space. partial anesthesia of the lower lip led to a loss of the waveform characteristics of tsef for electrical stimulation to the trigeminal nerve. we verified that the 20-ms latency cortical response of tsef components localized at the primary sensory cortex can serve as a robust neurofunctional marker of experimental trigeminal nerve dysfunction. © 2012 international & american associations for dental research.