Cantú Hiram, Nantel Julie, Millán Michelle, Paquette Caroline, Côté Julie N
Departamento de Ingeniería Biomédica, Vicerrectoría de Ciencias de la Salud, Universidad de Monterrey, San Pedro Garza García, Mexico.
Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, QC, Canada.
Front Neurol. 2019 Sep 3;10:951. doi: 10.3389/fneur.2019.00951. eCollection 2019.
Freezing of gait (FOG) is often experienced in advanced stages of Parkinson's disease (PD) and can lead to an increased risk of falls. Although spatiotemporal characteristics of FOG are well-described, their underlying neuromuscular mechanisms remain poorly understood. Several studies have demonstrated an abnormal activation of distal muscles of the lower limb and coordination impairments during gait in people with PD (pwPD). However, few have investigated how various characteristics of electromyograms (EMGs) change before, during and after a freezing episode (FE). Our objective was to quantify changes in proximal and distal leg muscle activity associated with FEs. In this study, 12 pwPD, confirmed as freezers, performed a repetitive stepping-in-place task used to elicit FE. Surface EMGs were collected from proximal [rectus femoris and biceps femoris (BF)] and distal [tibialis anterior (TA) and gastrocnemius medialis (GM)] muscles. Data epochs of 500 ms were extracted from EMG time series at four different periods: baseline, 2 s before a FE, during a FE, and 2 s after a FE. For each epoch, EMG amplitude [root-mean-square (RMS)], variability [coefficient of variation (CoV)], and inter-muscle functional connectivity (mutual information) were quantified. Results from the analysis of 21 FEs show a significant main effect of Period for EMG amplitude in bilateral TA and in the least affected GM ( < 0.01), with decreased activation before freezing that remained low during and after the FE. On the other hand, a main effect of Period was also found in bilateral BF muscles ( < 0.01) but with increased activation before freezing that was generally sustained during and after FE. Main effects of Period were also found for all measures of variability, except for the least affected GM, showing reduced variability during the FE that returned to baseline in all muscles except both TA. Moreover, an increase in functional connectivity between the least affected distal muscles was seen before the FE. Our findings confirm that many characteristics of EMG patterns of both distal and proximal leg muscles change throughout periods of a FE, suggesting both impairment and adaptive strategies from proximal muscles.
冻结步态（FOG）常在帕金森病（PD）晚期出现，会导致跌倒风险增加。尽管FOG的时空特征已有详尽描述，但其潜在的神经肌肉机制仍知之甚少。多项研究表明，帕金森病患者（pwPD）在步态过程中下肢远端肌肉激活异常且存在协调障碍。然而，很少有研究探讨肌电图（EMG）的各种特征在冻结发作（FE）之前、期间和之后如何变化。我们的目标是量化与FE相关的近端和远端腿部肌肉活动的变化。在本研究中，12名被确认为冻结步态者的pwPD进行了用于诱发FE的重复性原地踏步任务。从近端[股直肌和股二头肌（BF）]和远端[胫前肌（TA）和腓肠肌内侧头（GM）]肌肉采集表面肌电图。从肌电图时间序列中在四个不同时期提取500毫秒的数据片段：基线期、FE前2秒、FE期间和FE后2秒。对于每个片段，量化肌电图幅度[均方根（RMS）]、变异性[变异系数（CoV）]和肌肉间功能连接性（互信息）。对21次FE的分析结果显示，双侧TA和受影响最小的GM中，肌电图幅度的时期主效应显著（<0.01），冻结前激活降低，在FE期间和之后保持较低水平。另一方面，双侧BF肌肉中也发现了时期主效应（<0.01），但冻结前激活增加，在FE期间和之后通常持续。除受影响最小的GM外，所有变异性测量指标也发现了时期主效应，表明FE期间变异性降低，除双侧TA外的所有肌肉在FE后恢复到基线水平。此外，在FE前观察到受影响最小的远端肌肉之间的功能连接性增加。我们的研究结果证实，在FE的各个阶段，近端和远端腿部肌肉的肌电图模式的许多特征都会发生变化，这表明近端肌肉存在损伤和适应性策略。
