BACKGROUND Reduced intracortical inhibition is a neurophysiologic finding in focal dystonia that suggests a broader problem of impaired cortical excitability within the brain. A robust understanding of the neurophysiology in dystonia is essential to elucidate the pathophysiology of the disorder and develop new treatments. The cortical silent period (cSP) is a reliable, non-invasive method to measure intracortical inhibition in the primary motor cortex associated with a muscle of interest. In adductor spasmodic dysphonia (AdSD), cSP of the laryngeal motor cortex (LMC) which directly corresponds to the affected musculature, the thyroarytenoid (TA), has not been examined. OBJECTIVE This work evaluated the cSP of the LMC and the relationship between cSP and functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) activation in people with AdSD (n = 12) compared to healthy controls (CTL, n = 14). RESULTS Shortened LMC cSP were observed bilaterally in people with AdSD vs CTL (F(1, 99) = 19.5226, p < 0.0001), with a large effect size (η2 = 0.1834). Between-group fMRI analysis revealed greater activation in bilateral LMC in the AdSD > CTL contrast as compared to CTL > AdSD contrast. Correlation analysis showed that people with AdSD have positive correlation of left LMC BOLD activation and the cSP. Further, the right LMC cSP lacks either positive or negative associations with BOLD activation. CTL individuals displayed both positive and negative correlations between cSP and BOLD activation in the left LMC. In CTL, the LMC cSP and BOLD activation showed exclusively negative correlations in both hemispheres. CONCLUSION In AdSD, the cortical activation during phonation may not be efficiently or effectively associated with inhibitory processes, leading to muscular dysfunction. These findings may give insight into the maladaptive cortical control during phonation in people with AdSD.

中文翻译：

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经颅磁刺激和功能磁共振成像评估发声时内收肌痉挛性发声困难

背景皮质内抑制减少是局灶性肌张力障碍的神经生理学发现，表明大脑内皮质兴奋性受损的更广泛问题。对肌张力障碍的神经生理学的深入了解对于阐明该疾病的病理生理学和开发新的治疗方法至关重要。皮质静默期 (cSP) 是一种可靠的非侵入性方法，用于测量与感兴趣的肌肉相关的初级运动皮层的皮质内抑制。在内收肌痉挛性发声障碍 (AdSD) 中，喉部运动皮层 (LMC) 的 cSP 直接对应于受影响的肌肉组织甲状杓状肌 (TA)，尚未进行检查。目的 这项工作评估了 AdSD 患者 (n = 12) 与健康对照组 (CTL，n = 14）。结果 与 CTL 相比，AdSD 患者双侧 LMC cSP 缩短（F(1, 99) = 19.5226，p < 0.0001），效应大小较大（η2 = 0.1834）。组间功能磁共振成像分析显示，与 CTL > AdSD 对比相比，AdSD > CTL 对比中双侧 LMC 的激活程度更高。相关分析显示，AdSD 患者左 LMC BOLD 激活与 cSP 呈正相关。此外，右侧 LMC cSP 与 BOLD 激活缺乏正相关或负相关。CTL 个体在左侧 LMC 中的 cSP 和 BOLD 激活之间表现出正相关和负相关。在 CTL 中，LMC cSP 和 BOLD 激活在两个半球均显示出完全负相关。结论 在 AdSD 中，发声过程中的皮质激活可能无法有效地与抑制过程相关，从而导致肌肉功能障碍。这些发现可能有助于深入了解 AdSD 患者发声过程中皮质控制的适应不良。