Introduction

Following mild traumatic brain injury (mTBI), a substantial number of patients experience disabling fatigue for months after the initial injury. To date, the underlying mechanisms of fatigue remain unclear. Recently, it was shown that mTBI patients with persistent fatigue do not demonstrate increased performance fatigability (i.e., objective performance decline) during a sustained motor task. However, it is not known whether the neural activation required to sustain this performance is altered after mTBI.

Methods

Blood oxygen level-dependent (BOLD) fMRI data were acquired from 19 mTBI patients (>3 months post-injury) and 19 control participants during two motor tasks. Force was recorded from the index finger abductors of both hands during submaximal contractions and a 2-minute maximal voluntary contraction (MVC) with the right hand. Voluntary muscle activation (i.e., CNS drive) was indexed during the sustained MVC using peripheral nerve stimulation. Fatigue was quantified using the Fatigue Severity Scale (FSS) and Modified Fatigue Impact Scale (MFIS). Questionnaire, task, and BOLD data were compared across groups, and linear regression was used to evaluate the relationship between BOLD-activity and fatigue in the mTBI group.

Results

The mTBI patients reported significantly higher levels of fatigue (FSS: 5.3 vs. 2.6, p < 0.001). Both mTBI- and control groups demonstrated significant performance fatigability during the sustained MVC, but no significant differences in task performance or BOLD-activity were observed between groups. However, mTBI patients reporting higher FSS scores showed increased BOLD-activity in the bilateral visual cortices (mainly extrastriate) and the left midcingulate gyrus. Furthermore, across all participants mean voluntary muscle activation during the sustained MVC correlated with long lasting post-contraction BOLD-activation in the right insula and midcingulate cortex.

Conclusion

The fMRI findings suggest that self-reported fatigue in mTBI may relate to visual processing and effort perception. Long lasting activation associated with high levels of CNS drive might be related to changes in cortical homeostasis in the context of high effort.

中文翻译：

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轻度创伤性脑损伤后的疲劳与运动表现中的视觉处理和努力感知有关

介绍

轻度创伤性脑损伤 (mTBI) 后，大量患者在初次受伤后数月内会出现失能性疲劳。迄今为止，疲劳的潜在机制仍不清楚。最近，研究表明，持续性疲劳的 mTBI 患者在持续运动任务期间并未表现出疲劳性增加（即客观表现下降）。然而，尚不清楚维持这种表现所需的神经激活是否在 mTBI 后发生改变。

方法

血氧水平依赖性 (BOLD) fMRI 数据是从 19 名 mTBI 患者（伤后 > 3 个月）和 19 名对照参与者在两项运动任务中获取的。记录右手次最大收缩和 2 分钟最大随意收缩 (MVC) 期间双手食指外展肌的力。在使用周围神经刺激的持续 MVC 过程中对自愿肌肉激活（即 CNS 驱动）进行了索引。使用疲劳严重程度量表（FSS）和改良疲劳影响量表（MFIS）对疲劳进行量化。比较各组的问卷、任务和 BOLD 数据，并使用线性回归来评估 mTBI 组中 BOLD 活动与疲劳之间的关系。

结果

mTBI 患者的疲劳程度明显较高（FSS：5.3 vs. 2.6，p < 0.001）。mTBI 组和对照组在持续 MVC 期间都表现出显着的表现疲劳性，但组间在任务表现或 BOLD 活动方面没有观察到显着差异。然而，报告较高 FSS 评分的 mTBI 患者显示双侧视觉皮层（主要是纹状外）和左侧扣带回中 BOLD 活动增加。此外，在所有参与者中，持续 MVC 期间的随意肌肉激活与右侧岛叶和中扣带皮层的长期持续收缩后 BOLD 激活相关。

结论

功能磁共振成像研究结果表明，mTBI 患者自我报告的疲劳可能与视觉处理和努力感知有关。与高水平中枢神经系统驱动相关的持久激活可能与高强度背景下皮质稳态的变化有关。