Objective

Conventional time-series parameters are unreliable descriptors of motor-evoked potentials (MEPs) in brain tumor patients. Frequency domain analysis is suggested to provide additional information about the status of the cortico-spinal motor system. Aim of the present study was to describe the time-frequency representation of MEPs and its relation to the motor performance.

Methods

This study enrolled 17 consecutive brain tumor patients with impaired dexterity. After brain mapping of the affected (AH) and non-affected (NAH) hemisphere, TMS was applied to the hotspots of the abductor pollicis brevis muscles (APB). Using a Morlet wavelet approach, event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) of the MEPs were calculated and compared to the Grooved Pegboard Test (GPT). Additionally, inter- and intra-subject reliability was assessed by the intraclass correlation coefficient (ICC).

Results

MEPs were projecting to a frequency band between 30 and 400 Hz with a local maximum between 100 and 150 Hz. There was a significant ERSP and ITC reduction of the AH in comparison to the NAH. In contrast, no interhemispheric differences were depicted in the conventional time-series analysis. ERSP and ITC values correlated significantly with GPT results (r = 0.35 and r = 0.50). Time-frequency MEP description had good inter-and intra-subject reliability (ICC = 0.63).

Conclusions

Brain tumors affect corticospinal transmission resulting in a reduction of temporal and spectral MEP synchronization correlating with the dexterity performance.

Significance

Time-frequency representation of MEPs provide additional information beyond conventional time-domain features.

中文翻译：

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脑肿瘤患者运动诱发电位时频表征的半球间差异

客观的

传统的时间序列参数是脑肿瘤患者运动诱发电位 (MEP) 的不可靠描述符。建议进行频域分析以提供有关皮质脊髓运动系统状态的附加信息。本研究的目的是描述 MEP 的时频表示及其与运动性能的关系。

方法

该研究连续招募了 17 名灵巧性受损的脑肿瘤患者。在对受影响的 (AH) 和未受影响的 (NAH) 半球进行脑映射后，将 TMS 应用于拇短展肌 (APB) 的热点。使用 Morlet 小波方法，计算了 MEP 的事件相关光谱扰动 (ERSP) 和试验间相干性 (ITC)，并将其与凹槽钉板测试 (GPT) 进行比较。此外，通过组内相关系数 (ICC) 评估受试者间和受试者内的可靠性。

结果

MEP 投影到 30 到 400 Hz 之间的频带，局部最大值在 100 到 150 Hz 之间。与 NAH 相比，AH 的 ERSP 和 ITC 显着减少。相比之下，在传统的时间序列分析中没有描述半球间的差异。ERSP 和 ITC 值与 GPT 结果显着相关（r = 0.35 和 r = 0.50）。时频 MEP 描述具有良好的受试者间和受试者内可靠性（ICC = 0.63）。

结论

脑肿瘤影响皮质脊髓传输，导致与灵巧性能相关的时间和频谱 MEP 同步减少。

意义

MEP 的时频表示提供了超出传统时域特征的附加信息。