Palmer Jacqueline A, Zarzycki Ryan, Morton Susanne M, Kesar Trisha M, Binder-Macleod Stuart A
Division of Physical Therapy, School of Medicine, Emory University, Atlanta, Georgia
Department of Physical Therapy, University of Delaware, Newark, Delaware.
J Neurophysiol. 2017 Apr 1;117(4):1615-1624. doi: 10.1152/jn.00393.2016. Epub 2017 Jan 11.
Imbalance of corticomotor excitability between the paretic and nonparetic limbs has been associated with the extent of upper extremity motor recovery poststroke, is greatly influenced by specific testing conditions such as the presence or absence of volitional muscle activation, and may vary across muscle groups. However, despite its clinical importance, poststroke corticomotor drive to lower extremity muscles has not been thoroughly investigated. Additionally, whereas conventional gait rehabilitation strategies for stroke survivors focus on paretic limb foot drop and dorsiflexion impairments, most contemporary literature has indicated that paretic limb propulsion and plantarflexion impairments are the most significant limiters to poststroke walking function. The purpose of this study was to compare corticomotor excitability of the dorsi- and plantarflexor muscles during resting and active conditions in individuals with good and poor poststroke walking recovery and in neurologically intact controls. We found that plantarflexor muscles showed reduced corticomotor symmetry between paretic and nonparetic limbs compared with dorsiflexor muscles in individuals with poor poststroke walking recovery during active muscle contraction but not during rest. Reduced plantarflexor corticomotor symmetry during active muscle contraction was a result of reduced corticomotor drive to the paretic muscles and enhanced corticomotor drive to the nonparetic muscles compared with the neurologically intact controls. These results demonstrate that atypical corticomotor drive exists in both the paretic and nonparetic lower limbs and implicate greater severity of corticomotor impairments to plantarflexor vs. dorsiflexor muscles during muscle activation in stroke survivors with poor walking recovery. The present study observed that lower-limb corticomotor asymmetry resulted from both reduced paretic and enhanced nonparetic limb corticomotor excitability compared with neurologically intact controls. The most asymmetrical corticomotor drive was observed in the plantarflexor muscles of individuals with poor poststroke walking recovery. This suggests that neural function of dorsi- and plantarflexor muscles in both paretic and nonparetic limbs may play a role in poststroke walking function, which may have important implications when developing targeted poststroke rehabilitation programs to improve walking ability.
偏瘫侧与非偏瘫侧肢体之间皮质运动兴奋性的失衡与中风后上肢运动恢复的程度相关，受特定测试条件（如是否存在自主肌肉激活）的影响很大，并且可能因肌肉群而异。然而，尽管其具有临床重要性，但中风后对下肢肌肉的皮质运动驱动尚未得到充分研究。此外，虽然中风幸存者的传统步态康复策略侧重于偏瘫侧肢体足下垂和背屈障碍，但大多数当代文献表明，偏瘫侧肢体推进和跖屈障碍是中风后步行功能的最重要限制因素。本研究的目的是比较中风后步行恢复良好和恢复较差的个体以及神经功能正常的对照组在静息和活动状态下背屈肌和跖屈肌的皮质运动兴奋性。我们发现，在主动肌肉收缩期间但非静息期间，中风后步行恢复较差的个体中，与背屈肌相比，跖屈肌在偏瘫侧与非偏瘫侧肢体之间表现出皮质运动对称性降低。与神经功能正常的对照组相比，主动肌肉收缩期间跖屈肌皮质运动对称性降低是由于偏瘫侧肌肉的皮质运动驱动减少以及非偏瘫侧肌肉的皮质运动驱动增强所致。这些结果表明，偏瘫侧和非偏瘫侧下肢均存在非典型皮质运动驱动，并且表明在步行恢复较差的中风幸存者中，肌肉激活期间跖屈肌与背屈肌相比皮质运动损伤的严重程度更大。本研究观察到，与神经功能正常的对照组相比，下肢皮质运动不对称是由于偏瘫侧肢体皮质运动兴奋性降低和非偏瘫侧肢体皮质运动兴奋性增强共同导致的。在中风后步行恢复较差的个体的跖屈肌中观察到最不对称的皮质运动驱动。这表明偏瘫侧和非偏瘫侧肢体的背屈肌和跖屈肌的神经功能可能在中风后步行功能中起作用，这在制定有针对性的中风后康复计划以提高步行能力时可能具有重要意义。
