Lower extremity long-latency reflexes differentiate walking function after stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Motor Control

Background:

• Walking impairment after stroke is common, but underlying neural mechanisms, particularly in plantarflexor power generation, remain unclear.
• Understanding these mechanisms is crucial for targeted rehabilitation strategies.

Purpose of the Study:

• To investigate the association between long-latency reflex (LLR) responses and dynamic facilitation of antagonist motor-evoked responses with walking function in individuals post-stroke.
• To characterize neurophysiologic markers that differentiate stroke survivors with varying degrees of lower extremity motor impairment.

Main Methods:

• Fourteen individuals with chronic post-stroke hemiparesis and thirteen healthy controls performed isometric and dynamic plantarflexion.
• Transcranial magnetic stimulation (TMS) assessed supraspinal drive; LLR activity was measured during dynamic plantarflexion.
• Participants were classified as LLR present (LLR+) or absent (LLR-).

Main Results:

• LLR+ individuals post-stroke demonstrated better walking speeds and greater ankle plantarflexor power compared to LLR- individuals.
• LLR- individuals exhibited exaggerated TMS responses and dysfunctional modulation of stretch reflexes and antagonist supraspinal drive.
• Healthy controls and most post-stroke individuals exhibited LLRs, while a subset of five post-stroke individuals did not.

Conclusions:

• The presence or absence of LLRs and abnormal antagonist motor-evoked responses can distinguish between different profiles of motor impairment after stroke.
• These neurophysiologic markers provide clinically relevant information beyond standard behavioral assessments, aiding in understanding the heterogeneity of post-stroke motor deficits.
• Findings suggest potential for personalized rehabilitation approaches based on individual neurophysiologic profiles.