Clinical Neurosciences, Department of Clinical Neurophysiology, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Epilepsy Unit, Department of Pediatric Neurology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
PLoS One. 2018 Jul 2;13(7):e0200073. doi: 10.1371/journal.pone.0200073. eCollection 2018.
The intracarotid amobarbital procedure (IAP) is the current "gold standard" in the preoperative assessment of language lateralization in epilepsy surgery candidates. It is, however, invasive and has several limitations. Here we tested a simple noninvasive language lateralization test performed with magnetoencephalography (MEG).
We recorded auditory MEG responses to pairs of vowels and pure tones in 16 epilepsy surgery candidates who had undergone IAP. For each individual, we selected the pair of planar gradiometer sensors with the strongest N100m response to vowels in each hemisphere and-from the vector sum of signals of this gradiometer pair-calculated the vowel/tone amplitude ratio in the left (L) and right (R) hemisphere and, subsequently, the laterality index: LI = (L-R)/(L+R). In addition to the analysis using a single sensor pair, an alternative analysis was performed using averaged responses over 18 temporal sensor pairs in both hemispheres.
The laterality index did not correlate significantly with the lateralization data obtained from the IAP. However, an MEG pattern of stronger responses to vowels than tones in the left hemisphere and stronger responses to tones than vowels in the right hemisphere was associated with left-hemispheric language dominance in the IAP in all the six patients who showed this pattern. This results in a specificity of 100% and a sensitivity of 67% of this MEG pattern in predicting left-hemispheric language dominance (p = 0.01, Fisher's exact test). In the analysis using averaged responses over temporal channels, one additional patient who was left-dominant in IAP showed this particular MEG pattern, increasing the sensitivity to 78% (p = 0.003).
This simple MEG paradigm shows promise in feasibly and noninvasively confirming left-hemispheric language dominance in epilepsy surgery candidates. It may aid in reducing the need for the IAP, if the results are confirmed in larger patient samples.
颈动脉内苯巴比妥试验（IAP）是目前癫痫手术候选者语言侧化术前评估的“金标准”。然而，它具有侵入性且存在多种局限性。在此，我们测试了一种使用脑磁图（MEG）进行的简单非侵入性语言侧化测试。
我们记录了 16 名接受过 IAP 的癫痫手术候选者对元音和纯音的听觉 MEG 反应。对于每个个体，我们选择对每个半球中的元音具有最强 N100m 反应的一对平面梯度计传感器，并从该梯度计对的信号的矢量和中计算出左（L）和右（R）半球中元音/音的幅度比，然后计算出侧化指数：LI =（L-R）/（L+R）。除了使用单个传感器对进行分析之外，还使用在两个半球的 18 个时间传感器对上的平均响应进行了替代分析。
侧化指数与从 IAP 获得的侧化数据没有显著相关性。然而，在所有 6 名表现出这种模式的患者中，与 IAP 中左半球语言优势相关的模式是左半球对元音的反应强于对音，而右半球对音的反应强于元音。这导致该 MEG 模式预测左半球语言优势的特异性为 100％，敏感性为 67％（p = 0.01，Fisher 确切检验）。在使用时间通道上的平均响应进行分析时，在 IAP 中为左优势的另外 1 名患者表现出这种特殊的 MEG 模式，敏感性提高到 78％（p = 0.003）。
这种简单的 MEG 范式具有可行性和非侵入性，有望在癫痫手术候选者中可靠地确认左半球语言优势。如果在更大的患者样本中得到证实，则可能有助于减少对 IAP 的需求。
