Kang Dezhi, Yao Peisen, Wu Zanyi, Yu Lianghong
Neurosurgery of The First Affiliated Hospital of Fujian Medical University, No. 88, Jiaotong Road, Taijiang District, Fuzhou, China.
Clin Neurol Neurosurg. 2013 May;115(5):552-6. doi: 10.1016/j.clineuro.2012.06.029. Epub 2012 Jul 12.
We assessed the relationship between cerebral ischemia-induced changes in evoked potentials and the degree of ischemia tolerance.
47 patients underwent somatosensory evoked potential (SEP) and motor evoked potential (MEP) monitoring in intracranial aneurysm surgery. Three duration parameters (time) were recorded: Time 1, from the starting of temporary occlusion unavoidable in aneurysm surgery to the time the evoked potentials decrease from basal level to reaching the warning criterion; Time 2, from evoked potentials reaching the warning criterion to the time the blood flow was resumed; Time 3, after resuming the blood flow, the time it took the evoked potentials to recover to baseline. All three times can be reliably calculated in the SEP recording, but not in the MEP recording which consisted of either unchanged amplitudes or abruptly changing amplitudes, making it impossible to obtain Time 1. The ischemic tolerance ratio (ITR) was calculated as ITR=time 2/time 1×100%. New decreasing myodynamia and fresh infarction after the surgery were employed for evaluating neurological deficits postoperatively, and their correlations with the ischemia-induced changes of evoked potentials recorded during the surgery were analyzed.
We found a change in SEPs in 12 patients whose cerebral ischemia was induced by temporary occlusion of the aneurysm's parent artery. We also found the development of postoperative neurological deficits in 4 patients whose ischemic tolerance ratio (ITR) reached over 80%, while no deficits were found in the other 8 patients whose ITR was less than 50%. MEP changes were seen in 4 patients whose cerebral ischemia was caused by accidentally clamping the perforating branches, causing the development of postoperative neurological deficits but not necessarily leading to significant SEP changes.
The Ischemia tolerance ratio (ITR) in SEP recordings is valuable to predicting postoperative neurological deficits caused by temporary occlusion of aneurysm's parent artery. Maintaining the ITR under 50% during operation can effectively avoid postoperative neurological deficits, while an ITR above 80% reliably forecasts postoperative neurological deficits. Complementary to SEPs, MEP recordings are particularly valuable in monitoring ischemic effects caused by accidentally clamping perforating branches. Taken together, this system of monitoring makes it possible to promptly adjust surgery procedures and minimize postoperative neurological deficits.
我们评估了脑缺血诱导的诱发电位变化与缺血耐受程度之间的关系。
47例患者在颅内动脉瘤手术中接受了体感诱发电位（SEP）和运动诱发电位（MEP）监测。记录了三个持续时间参数（时间）：时间1，从动脉瘤手术中不可避免的临时阻断开始到诱发电位从基础水平下降到达到预警标准的时间；时间2，从诱发电位达到预警标准到恢复血流的时间；时间3，恢复血流后，诱发电位恢复到基线所需的时间。在SEP记录中可以可靠地计算出所有这三个时间，但在由振幅不变或突然变化组成的MEP记录中则无法计算，因此无法获得时间1。缺血耐受率（ITR）计算为ITR = 时间2 / 时间1×100%。术后新发肌力减弱和新鲜梗死用于评估术后神经功能缺损，并分析它们与手术期间记录的缺血诱导的诱发电位变化之间的相关性。
我们在12例因临时阻断动脉瘤供血动脉而导致脑缺血的患者中发现了SEP变化。我们还发现，4例缺血耐受率（ITR）超过80%的患者出现了术后神经功能缺损，而其他8例ITR低于50%的患者未发现缺损。4例因意外夹闭穿支而导致脑缺血的患者出现了MEP变化，导致术后神经功能缺损，但不一定导致明显的SEP变化。
SEP记录中的缺血耐受率（ITR）对于预测由临时阻断动脉瘤供血动脉引起的术后神经功能缺损具有重要价值。术中将ITR维持在50%以下可有效避免术后神经功能缺损，而ITR高于80%则可可靠地预测术后神经功能缺损。作为SEP的补充，MEP记录在监测意外夹闭穿支引起的缺血效应方面特别有价值。综上所述，这种监测系统使得能够及时调整手术程序并将术后神经功能缺损降至最低。
