Somatosensory evoked potential (SEP) monitoring is a standard tool during clipping of aneurysms of the middle cerebral artery (MCA), and the parameter used to detect a state of cortical ischemia is amplitude. We think that the sensitivity of SEP can however be improved by using other parameters. Our study moves in this direction via SEP morphology. In this pilot preliminary study, involving a small sample without postoperative neurological deficit, we aimed at investigating the value of SEP morphology (in the 15- to 35-ms time frame), in comparison with SEP amplitude (N20 peak-to-peak), as a measure of sensitivity to blood flow reduction. The changes in the SEP morphology of 16 patients undergoing clipping of an unruptured MCA aneurysm was studied. We applied the Morph-Fréchet index for each recorded SEP (at 30-second intervals), quantifying the pattern shape change with regard to the average SEP recorded after dura opening (baseline). We also compared 3 measurements of the SEP morphology, without and with GARCH-derived filter. Filtered Morph-Fréchet never exceeded the individual’s “normality” range in baseline but did so in 81% of the risk phase on average across the 16 subjects, which is more than that for amplitude (36%, P = .002). This pilot study indicates that a measurement derived from the networking nature of the brain was sensitive to blood flow reduction. The SEP morphology approach promises to improve SEP monitoring sensitivity during clipping of unruptured MCA aneurysms. New and Noteworthy. The higher sensitivity to blood flow reduction of SEP morphology than amplitude promises to improve the effectiveness of intraoperative monitoring during MCA aneurysm clipping procedures.

中文翻译：

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大脑中动脉夹闭 (MoSAC) 期间体感诱发电位的形态学：一项初步研究

体感诱发电位 (SEP) 监测是大脑中动脉 (MCA) 动脉瘤夹闭期间的标准工具，用于检测皮质缺血状态的参数是振幅。然而，我们认为可以通过使用其他参数来提高 SEP 的灵敏度。我们的研究通过 SEP 形态朝着这个方向发展。在这项试验性初步研究中，涉及没有术后神经功能缺损的小样本，我们旨在研究 SEP 形态（在 15 到 35 毫秒的时间范围内）与 SEP 振幅（N20 峰峰值）相比的价值，作为对血流量减少的敏感性的量度。研究了 16 名接受未破裂 MCA 动脉瘤夹闭的患者的 SEP 形态变化。我们为每个记录的 SEP 应用 Morph-Fréchet 指数（以 30 秒为间隔），根据硬脑膜打开（基线）后记录的平均 SEP 量化图案形状变化。我们还比较了 SEP 形态的 3 个测量值，没有和有 GARCH 派生的过滤器。过滤后的 Morph-Fréchet 从未超出个人基线的“正常”范围，但在 16 名受试者中平均 81% 的风险阶段超过了这一范围，这超过了幅度（36%，P = .002）。这项初步研究表明，源自大脑网络性质的测量结果对血流量减少很敏感。SEP 形态学方法有望提高未破裂 MCA 动脉瘤夹闭期间 SEP 监测的灵敏度。新的和值得注意的。