皮質電気刺激によるヒト脳機能ネットワークの探索 [in Japanese] Probing Functional Brain Networks with Cortical Electrical Stimulation [in Japanese]
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術後の脳機能温存のためには脳局所の機能だけでなく, 皮質間ネットワークの把握が重要である. 単発電気刺激 (1Hz) を皮質に与え皮質皮質間伝播を介した皮質・皮質間誘発電位を計測することで, 刺激部位と誘発電位記録部位間の皮質間結合を優れた時間空間分解能で機能的に探索できる. 高頻度電気刺激 (50Hz) で刺激部位の機能を同定し, 両者の刺激を組み合わせることで皮質間ネットワークのマッピングが可能である. この手法を覚醒下手術中の皮質・白質刺激に応用し, 背側言語経路に関わる白質線維束の機能同定と結合する皮質の追跡に成功した. 弓状束の術中機能モニタリング法として今後の臨床応用・普及が期待される.
The preservation of brain function during and after surgery still poses a challenge for neurosurgeons. High-frequency electrical stimulation techniques have been established in order to map the intraoperative brain function and preserve the eloquent areas during surgery. In addition to this functional cortical mapping, the subcortical fibers related to eloquent function have been extensively investigated by using high-frequency electrical stimulation. However, these cortical- and subcortical high-frequency electrical stimulation methods are only able to identify the local function (i. e., stimulus site). Even during awake craniotomy, no monitoring methods have as yet been established to preserve the integrity of the language network during surgery, as opposed to the monitoring methods utilizing motor evoked potentials for the motor network.<br> We have recently developed an <i>in vivo</i> electrical tract tracing method using cortico-cortical evoked potentials (CCEPs). In an extraoperative setting for presurgical evaluation of epilepsy surgery, single-pulse electrical stimulation was applied directly to the cortex, and CCEPs were recorded from the adjacent and remote cortices through cortico-cortical connections. In an extraoperative setting, this method has successfully probed eloquent brain functional networks such as the language and motor networks. Because of the high reproducibility and reliability, CCEP technique could be applicable in an intraoperative setting to identify and monitor functionally eloquent networks.<br> In our pilot intraoperative CCEP study, using CCEP connectivity patterns, we were able to map the anterior and posterior perisylvian language areas. Combined single-pulse and high-frequency electrical stimulation to the removal cavity (white matter) delineated both the function and cortical terminations of the dorsal language pathway. Although further case studies are necessary to establish a clear cut-off value to prevent language dysfunction, intraoperative CCEP monitoring is clinically useful for evaluating the integrity of the dorsal language network.
- Japanese Journal of Neurosurgery
Japanese Journal of Neurosurgery 25(5), 411-420, 2016
The Japanese Congress of Neurological Surgeons