[Trigeminal somatosensory evoked potentials: I. Recording technic and normal responses].
The general wave form and time course of somatosensory evoked potentials (SEP) to the stimulation of upper and lower extremities has been well known in recent years. However, only a little information has been published so far on SEP to the trigeminal nerve stimulation (TSEP), and at present there is not always common methodology available in clinical practice. These may be due to the technical problems from the close proximity of stimulating and recording electrodes. The purpose of this report is to attempt to solve some of the difficulties of the procedure, as well as to show the morphology and time course of TSEP in a group of normal healthy subjects. Twenty healthy volunteers were investigated. Their age ranged from 22 to 61 years old (mean 29.3). Clip shaped silver-balled stimulating electrodes with 2 mm contact surface and interelectrode distance of 10 mm were applied to the inner surface of the lips. They were held in place without any support, thus minimizing muscle activity of the subject. Each half of the upper and lower lip was then stimulated in turn by an electrical rectangular pulse of 3 or 4 times sensory threshold (usually 1.5-2.0 mA) and 0.2 msec duration, at a rate of 2.3 per second. TSEP was recorded contralaterally from C'5 or C'6 (midpoint between Cz and external auditory porus). Fz was used as a reference. Four hundred responses were averaged by a Nicolet Pathfinder II, which also generated stimulation pulses. Stimulus polarity was reversed after each 100 stimuli to eliminate stimulus artifact. Analysis time was set to 50 msec.(ABSTRACT TRUNCATED AT 250 WORDS)
D000328:Adult; D004558:Electric Stimulation; D004566:Electrodes; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008046:Lip / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011930:Reaction Time; D012684:Sensory Thresholds; D014276:Trigeminal Nerve / Q000502:physiology*