A NEW METHOD OF MULTISEGMENT MOTOR PATHWAY MONITORING USING MUSCLE POTENTIALS AFTER TRAIN SPINAL STIMULATION

Study Design. Evoked muscle and nerve action potentials after spinal stimulation for intraoperative monitoring were investigated using a modified stimulation technique. Animal experiments and clinical application were performed. Objectives. To contrive a useful method of intraoperative motor pathway monitoring under inhalation anesthesia. Summary of Background Data. Many different kinds of procedures have been reported. No reliable method that reflects pure motor tract function has been established. Methods. Characteristic of our stimulating technique was the use of numbered consecutive pulses (''train stimulation''). In 16 cats, optimum condition of train stimulation, effects of anesthetic agents , and conductive pathway were examined. In 35 patients, muscle potentials evoked by train stimulation were recorded, and clinical usefulness was evaluated. Results. In the experimental study, the optimum stimulus condition was determined 1 ms interstimulous interval train of five pulses. Conductive pathway of this method was identified as a lateral column by selective spinal cord transection. In the clinical application, by using train stimulation, multisegmental muscle potentials were obtainable even using inhalation anesthetics. Conclusions. The facilitative effects of train stimulation, attributed to temporal summation, are considered to overcome the suppression of inhalation anesthesia. The evoked muscle potentials by train spinal stimulation reflect the functions of pure motor tract and is the only, extremely efficient method for intraoperative motor pathway monitoring.