Utilization of motor evoked potentials for the intraoperative spinal cord monitoring-study on the prevention and fixation of the spinal cord injury

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09671513
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Orthopaedic surgery
• Research Institution: Wakayama Medical College
• Principal Investigator: TAMAKI Tetsuya Wakayama Medical College, Professor, 医学部, 教授 (30009592)
• Co-Investigator(Kenkyū-buntansha): YAMADA Hiroshi Wakayama Medical College, Assistant, 医学部, 助手 (70275361) ; ANDO Muneharu Wakayama Medical College, Assistant, 医学部, 助手 (40264890)
• Project Period (FY): 1997 – 1998
• Keywords: spinal cord monitoring / motor evoked potential / compound muscle action potential / ischemic insult

Research Abstract

In recent years, potentials delivered through the motor related tracts have been advocated for the intra-operative spinal cord monitoring. Especially the use of the compound muscle action potential (CMAP) has been regarded to offer optimal information to monitor the motor function, although, we have to call attention of the practical users to the potential problems with CMAP.They are 1. Effect and elimination of anesthesia, 2.Problems related to the hypersensitivity of CMAP that means the discrepancy between the CMAP disappearance and postoperative motor ysfunction, 3. Understanding of the physiological mechanism of the hypersensitivity of CMAP against the insults to the spinal cord. We could show the use of stimulation of 2 to 5 trains with 1-2msec interval could eliminate the effect of inhalation anesthetic substance on the anterior motor neurons. Furthermore, we could demonstrate that the disappearance of CMAP is not directory indicate the impairment of the motor function. In another wards, despite CMAP decrease in amplitude responding to the slight insult to the spinal cord the animal woke up with any neurological sequela. Further insult which produced around 50% decrement of the conductive potentials such as SCEP (spinal cord evoked potential) and MEP (motor evoked potential recorded from the spinal cord after the brain stimulation) left high incidence of motor paralysis in animals. On the basis of above mentioned results, we recommend the concomitant use of CMAP with conductive potentials. The mechanism of the hypersensitivity of CMAP has been left for future study.