The masseter motor-evoked potential after transcranial magnetic stimulation in patients with sleep bruxism / 实用口腔医学杂志

Objective:To study the masseter motor evoked potential(MEP)in patients with sleep bruxism(SB)and in healthy con-trols.Methods:30 subjects with SB and 30 healthy controls were included.MEPs were obtained by transcranial magnetic stimulation (TMS).Tests were done during daytime when the subjects were awake.The data were statistically analysed.Results:In the patients AMT was 55(52,55)%,latency of c-MEP (6.7 ±1.3)ms,the amplitude of c-MEP 0.19(0.15,0.29)mV,latency of r-MEP (2.3 ±0.4)ms,the central conduction time(CCT)4.4(3.3,5.2)ms.In the control subjects AMT was 52(52,55)%,latency of c-MEP (6.4 ±0.7)ms,the amplitude of c-MEP 0.23(0.17,0.28)mV,latency of r-MEP (2.4 ±0.4)ms,CCT 4.0 (3.4,4.4) ms.No significant difference was found between the 2 groups in the measurements evoked by TMS.Conclusion:The MEP after TMS in patients with SB is similar to that of healthy subjects,indicating that the excitability of the cortical motor system is not changed in bruxism subjects,at least when evaluated by TMS.

Analysis of Intraoperative Neurological Complications in High-Risk Spinal Surgery with the Use of Motor Evoked Potential Monitoring

STUDY DESIGN: This is retrospective study. OBJECTIVES: To evaluate the risk of operative techniques using Motor Evoked Potential (MEP) in high-risk spinal surgery. SUMMARY OF LITERATURE REVIEW: There are few studies regarding the evaluation of operative techniques by MEP. MATERIALS AND METHODS: We studied 33 cases that had MEP during surgery from July 2007 to March 2009. Diagnoses included post-traumatic kyphosis (PTK) in eight cases, congenital deformity in eight cases, degenerative lumbar deformity in eight cases, ankylosing spondylitis (AS) in three cases, spinal tumor in three cases, adjacent segmental disease in two cases, and post-surgical kyphosis in one case. Posterior vertebral column resection (PVCR) and pedicle subtraction osteotomy (PSO) were performed in 27 cases (81.8%) and, in the others, posterior decompression with discectomy was performed. We analyzed the risk of operative techniques and evaluated the MEP. RESULTS: MEP showed abnormal signal change in five cases (PVCR: one case, compression and distraction: four cases). The AS case did not demonstrate neurological change after surgery. Though the PTK on T12 operated by PVCR case did not show an abnormal MEP result, neurological change was observed postoperatively. The sensitivity, specificity, percent of false negatives, and percent of false positives of MEP were 80.0%, 96.4%, 20.0%, and 3.6%, respectively. CONCLUSIONS: MEP monitoring is a useful method to detect neurological injury during high-risk spinal surgery with satisfactory specificity. For low sensitivity and a high false negative rate, increased monitoring of cases and continuous follow-up is needed. In conclusion, compression and distraction and PVCR are high-risk techniques in kyphotic deformity correction.

Effect of Voluntary Contraction in Motor Evoked Potential and Silent Period by Transcranial Magnetic Stimulation

OBJECTIVE: To determine the effects of the voluntary contraction of muscles and magnetic stimulation intensity on the motor evoked potential (MEP) and the silent period (SP). METHOD: We studied MEPs and SPs in opponens pollicis muscle in 30 healthy adults (male: 16, female: 14) while varying the amount of the voluntary contraction and the stimulation intensity. We analyzed MEPs and SPs in relation to sex, recording site, opposition power and height. RESULTS: 1) During the contraction, the latencies of MEP were significantly shorter than during the relaxation. 2) The amplitudes of MEP reached plateau at 30% of maximal voluntary contraction and increased with increment of stimulation intensity without limitation. The amplitudes of MEP of right hand were bigger than left hand. There were no significant differences according to sex and recording site. 3) The durations of SP were directly proportional to the degrees of voluntary contraction and the stimulation intensity. CONCLUSION: Transcranial magnetic stimulation should be performed under the same voluntary contraction and magnetic stimulation intensity.