Comparing cortico-motor hotspot identification methods in the lower extremities post-stroke: MEP amplitude vs....

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Transcranial magnetic stimulation (TMS) is vital for assessing nervous system responses.
• Developing specific lower extremity (LE) TMS methods, particularly post-stroke, remains a challenge.
• Accurate identification of motor cortical hotspots is crucial for targeted neuromodulation.

Purpose of the Study:

• To compare motor evoked potential amplitude (MEP_amp) and latency (MEP_lat) for identifying tibialis anterior and soleus motor hotspots post-stroke.
• To determine which metric, MEP_amp or MEP_lat, offers greater consistency in hotspot localization.
• To inform the development of standardized LE TMS protocols for stroke research.

Main Methods:

• Retrospective analysis of 23 stroke participants.
• Neuronavigation used to map hotspots based on MEP_amp and MEP_lat over a defined grid.
• Comparison of spatial distances between identified hotspots within sessions and between days.

Main Results:

• Both MEP_amp and MEP_lat showed poor identification of hotspots between trials and visits.
• MEP_amp provided more consistent hotspot identification than MEP_lat.
• Hotspots identified by MEP_amp were spatially closer within sessions (1.4 cm vs 1.7 cm) and between days (1.3 cm vs 1.9 cm) compared to MEP_lat (P < 0.01 for both).

Conclusions:

• MEP_amp is a more consistent metric than MEP_lat for identifying lower extremity motor cortical hotspots in stroke patients.
• Further research is needed to refine LE TMS methodology, especially for gait-related studies.
• MEP_amp is recommended for future studies using neuronavigation to identify tibialis anterior and soleus hotspots.