Bartley Kathleen, Woodforth Ian J, Stephen John P H, Burke David
Department of Clinical Neurophysiology, Prince of Wales and Sydney Children's Hospitals, Sydney, Australia.
Clin Neurophysiol. 2002 Jan;113(1):78-90. doi: 10.1016/s1388-2457(01)00711-8.
To report our experience with neurophysiological monitoring of corticospinal function using compound muscle action potentials (CMAPs) produced by repetitive transcranial electrical stimulation in a large series of patients, after defining optimal stimulus parameters in a small group of patients.
In 100 patients undergoing spinal surgery, corticospinal volleys were recorded using epidural electrodes, or CMAPs were recorded from innervated muscles, or both techniques were used to monitor spinal cord function. In subsets of patients, stimulus parameters were varied to determine the optimal parameters for CMAP recordings, using the corticospinal volleys to guide the initial choice.
Recordings of corticospinal volleys indicated that less energy was delivered to the cortex if the duration of each stimulus in the stimulus train was brief (e.g. 50 micros) and that there was attenuation of D and I waves in the corticospinal volley when the interstimulus interval in the train was <5 ms. An interstimulus interval of 5 ms proved significantly more effective than an interstimulus interval of 2 ms in evoking CMAPs, but resulted in a more complex, dispersed electromyographic (EMG) potential. The superiority of the 5 ms interval did not depend on stimulus intensity or the existence of pre-existing neurological deficit. Using trains of 5 pulses of duration 50 micros, interstimulus interval 5 ms and intensity 500 V, satisfactory CMAPs could be recorded in 55 of 82 patients, significantly less often in neurologically impaired patients than in neurologically normal subjects. Epidural recordings of the corticospinal volley were obtained in 61 of 69 patients, again more often in neurologically normal subjects.
When epidural recordings can be made, direct recordings of corticospinal activity are probably more reliable than recordings of CMAPs. However, epidural recordings are not suitable under all circumstances, and the ability to record CMAPs reliably represents an advance in intraoperative monitoring. Under the anaesthetic conditions used in the present study, the optimal stimulus parameters consist of a train of 5 stimuli of 50 micros duration at an interstimulus interval of 5 ms and an intensity of 500 V.
在一小部分患者中确定最佳刺激参数后，报告我们在大量患者中使用重复经颅电刺激产生的复合肌肉动作电位（CMAP）对皮质脊髓功能进行神经生理监测的经验。
对100例接受脊柱手术的患者，使用硬膜外电极记录皮质脊髓冲动，或从受支配肌肉记录CMAP，或两种技术均用于监测脊髓功能。在部分患者亚组中，改变刺激参数以确定CMAP记录的最佳参数，最初的选择以皮质脊髓冲动为指导。
皮质脊髓冲动记录表明，如果刺激串中每个刺激的持续时间较短（例如50微秒），则传递到皮质的能量较少；当刺激串中的刺激间隔<5毫秒时，皮质脊髓冲动中的D波和I波会衰减。事实证明，5毫秒的刺激间隔在诱发CMAP方面比2毫秒的刺激间隔显著更有效，但会导致更复杂、分散的肌电图（EMG）电位。5毫秒间隔的优势不取决于刺激强度或既往神经功能缺损的存在。使用持续时间50微秒、刺激间隔5毫秒、强度500伏的5个脉冲串，82例患者中有55例可记录到满意的CMAP，神经功能受损患者的记录成功率明显低于神经功能正常的受试者。69例患者中有61例获得了皮质脊髓冲动的硬膜外记录，同样神经功能正常的受试者记录成功率更高。
当可以进行硬膜外记录时，皮质脊髓活动的直接记录可能比CMAP记录更可靠。然而，硬膜外记录并非在所有情况下都适用，可靠记录CMAP的能力代表了术中监测的一项进步。在本研究使用的麻醉条件下，最佳刺激参数包括一串5个持续时间50微秒的刺激，刺激间隔为5毫秒，强度为500伏。
