诱发电位监测在显微外科手术治疗颅内动脉瘤中的初步应用

背景 近年来显微外科手术技巧取得很大的进步,然而颅内动脉瘤手术仍然存在众多并发症.多种术中特定手术操作造成的大脑功能区缺血与术后神经系统功能损伤有关.为进一步提高颅内动脉瘤手术的安全性、减少术后脑缺血性并发症的发生,有必要在术中对相应脑血管供血区域的缺血性损伤进行实时的监测.我们在颅内动脉瘤显微外科手术中联合应用运动诱发电位(MEPs)、体感诱发电位(SSEPs)及脑干听觉诱发电位(BAEPs)监测,提高术中诱发电位(EPs)信号改变对特定手术步骤导致脑缺血的敏感性,并研究它们与术后神经功能结果之间的关联性.方法 我们于2006年3月至2006年8月对我院25例采用显微手术的动脉瘤患者联合应用MEPs、SSEPs和BAEPs进行术中监测.对22例前循环动脉瘤手术,单纯行SSEPs监测4例,行MEPs及SSEPs监测18例,对3例后循环动脉瘤手术同时监测MEPs、SSEPs及BAEPs,将术中监测结果与术后神经功能作前瞻性观察研究.①SSEPs监测记录及刺激电极均采用皮下针电极.监测上肢SSEPs时,按国际脑电学会制定(10～20)系统,参考电极放在Fz,记录电极放在C3'、C4'和双侧Erb点,分别记录双侧皮质电位和外周电位.刺激电极放在腕部左右正中神经,刺激强度为15～25 mA,刺激间期0.2 ms,刺激频率3.1 Hz,波带通50～300 Hz,分析时间50 ms.监测下肢SSEPs时,记录电极置于Cz和双侧腘窝,分别记录双侧皮质电位和腘窝电位.刺激电极放在内踝部左右胫后神经,刺激强度为20～30 mA,记录参数与上肢SSEPs监测相同.术中主要观察手术侧皮质电位(上肢为N20波,下肢为P37波).所有波形均以麻醉后40 min SSEPs的值为标准,警报标准为波幅降低大于基线的50%或潜伏期延长10%.②MEPs监测采用外接电刺激器(Digitimer D 185 stimulator),刺激电极采用螺旋塞电极,记录电极采用皮下针电极.刺激电极放在C3/C4或C1/C2前1～2 cm,阴极放在对侧相应的地方.刺激采用恒流经颅连续短串电刺激5个单相方波,阳极刺激,持续时间300μs,刺激间隔2 ms(重复频率500 Hz),最大刺激电压600 V.记录从双侧肱二头肌、拇短展肌、胫前肌和拇展肌诱发的肌源性MEPs.警报标准为肌原性MEPs波幅消失.采用四联刺激肌肉收缩试验(TOF)监测神经肌肉反应活动.③BAEPs监测记录电极采用皮下针电极,置于两侧乳突.参考电极置于头顶(Cz).耳道插入式短声刺激.11.1 Hz疏密波,100 dBnHL级,对侧耳道60 dBnHL白噪音掩蔽.波带通30～1 500 Hz,分析时间15 ms,叠加1 000次.警报标准为V波潜伏期延长大于0.8 ms或波幅降低大于基线的50%.麻醉维持采用异丙芬、芬太尼、异氟醚、N2O和万可松,控制吸入性麻醉剂和肌松药的用量.结果 对载瘤动脉临时阻断、载瘤及临近重要血管的误夹、过度脑牵拉、血管痉挛或小穿支血管损害等术中事件引起的脑缺血,MEPs5/21、SSEPs5/25、BAEPs1/3出现异常.3例术后出现新的肢体运动功能障碍病人中,术中均有MEPs异常,而SSEPs仅1例异常.术中EPs未出现异常的病例,术后均未出现新的神经功能障碍.结论 通过本组初步研究,笔者认为MEPs监测对于运动系统缺血性损伤的敏感性优于SSEPs监测,术中EPs信号改变与术后神经功能结果之间具有良好的关联性,而稳定的EPs联合监测有助于预测健全的感觉运动功能,并且保证足够的远端侧支血流量,允许术者安全地完成潜在危险性的操作.

The primary application of intra-operative evoked potentials monitoring in microsurgery of intracranial aneurysms

Background Although remarkable progress has been made in microsurgery, surgery of intracranial aneurysm still encounters various complications. Cerebral ischemia and postoperative disorders of nervous system could be induced by various specific operation procedures. To improve the outcomes in intracranial aneurysm surgery and to minimize the occurrence of postoperative ischemic complications, it is necessary to perform real-time monitoring on ischemic damages for the corresponding functional areas. To elevate the sensitivity of EPs changes for the detection of cerebral ischemia induced by operation, we monitored Motion Evoked Potential (MEPs), Somatosensory Evoked Potential (SSEPs)and Brainstem Auditory Evoked Potential (BAEPs) in microsurgical operations of intracranial aneurysms. And then the correlation between EPs changes and clinical outcome was investigated. Methods MEPs, SSEPs, and BAEPs were recorded intra-operatively for 25 cases in intracranial aneurysms. Monitored results and clinical outcome were analyzed in a prospective observational design. Results The MEPs in 5 of 21 cases, the SSEPs in 5 of 25 cases and the BAEPs in 1 of 3 cases showed inadequate temporary clipping, inadvertent occlusion, inadequate retraction, vasospasm, or compromise to perforating vessels. 3 patients developed advanced weakness, which showed abnormal SSEPs in only one patient while showed abnormal MEPs in all 3 cases. Conclusions The MEPs is more sensitive than SSEPs in monitoring the motor ischemic impairments. The monitoring results were correlated to the clinical outcome closely. Monitoring EPs in keyhole microsurgery of intracranial aneurysms could improve the sensitivity in detecting insufficient distal collateral flow. And then successful completion of potentially hazardous maneuvers would be attained.