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Neurological Surgery No Shinkei Geka Volume 47, Issue 9 （September 2019）

Neurological Surgery 脳神経外科 47巻9号（2019年9月発行）

Japanese English

テクニカル・ノート

皮質・白質刺激強度相対値を用いた皮質下刺激運動誘発電位による錐体路マッピング Corticospinal Tract Mapping by Calculating the Ratio of Subcortical to Cortical Stimulation Intensity:A Technical Note 蛭田亮 ^1,2 , 藤井正純 ² , 古川佑哉 ^1,2 , 市川剛 ¹ , 鈴木恭一 ¹ , 渡部洋一 ¹ , 根本未緒 ² , 佐藤拓 ² , 佐久間潤 ² , 齋藤清 ² Ryo HIRUTA ^1,2 , Masazumi FUJII ² , Yuya FURUKAWA ^1,2 , Tsuyoshi ICHIKAWA ¹ , Kyouichi SUZUKI ¹ , Yoichi WATANABE ¹ , Mio NEMOTO ² , Taku SATO ² , Jun SAKUMA ² , Kiyoshi SAITO ² ¹福島赤十字病院脳神経外科 ²福島県立医科大学脳神経外科 ¹Department of Neurosurgery, Fukushima Red Cross Hospital ²Department of Neurosurgery, Fukushima Medical University キーワード： subcortical mapping , motor evoked potential , corticospinal tract , glioblastoma , nitrous oxide Keyword: subcortical mapping , motor evoked potential , corticospinal tract , glioblastoma , nitrous oxide pp.957-960

発行日 2019年9月10日 Published Date 2019/9/10

DOI https://doi.org/10.11477/mf.1436204054

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Abstract 文献概要
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参考文献 Reference

Ⅰ．はじめに

　錐体路（cortico spinal tract：CST）近傍腫瘍の手術において，白質（皮質下）電気刺激により運動誘発電位（motor evoked potential：MEP）が得られる刺激閾値を測定し，刺激部位からCSTまでの距離を推定する手法が報告されている^1,6)．これらの報告では刺激強度の絶対値が用いられているが，MEPは麻酔薬や麻痺，刺激条件などさまざまな影響を受けるため⁴⁾，距離の推定は必ずしも正確でない可能性があり注意を要する．皮質刺激強度（電流値）と白質直接刺激強度の相対値を用いる方法⁵⁾は，刺激電流の絶対値に比べてこれらの影響を軽減できる可能性があり，自験例を交えて報告する．

　OBJECTIVE：Motor evoked potentials（MEPs）have been developed and utilized as safe surgical procedures. A correlation between the threshold intensity of direct stimulation MEPs and the distance of the corticospinal tract（CST）has been already established. However, MEPs are affected by anesthesia and patient-related conditions. Here, we describe a unique technique to avoid these effects.

　METHOD：When tumors developed in proximity to the CST, the transcortical MEP monitoring was done by placing grid electrodes on the primary motor cortex continuously while direct subcortical MEP mapping was conducted with a monopolar probe. The ratios of the subcortical to the transcortical stimulation intensity were calculated. The point at which the ratios reached 50% was defined as the surgical excision limit.

　DISCUSSION：MEPs are affected by anesthesia, paralysis, body temperature, and other factors. By measuring the ratio of the cortical stimulation intensity instead of the absolute value of the white matter stimulation intensity, various affecting factors can be avoided, and more accurate monitoring can become possible.

　CONCLUSION：By calculating the ratio of subcortical to cortical stimulation intensity, the corticospinal tract mapping is less likely to be influenced by the stimulation condition or facility setup, and this warrants further investigation.