Inter-pulse interval and motor evoked potential variability: Bridging insights from healthy adults to post-stroke TMS protocols

Transcranial Magnetic Stimulation (TMS) is a non-invasive brain stimulation technique widely used to assess the functional integrity of the contralateral corticospinal tract (CST). Single-pulse TMS (spTMS) elicits contralateral motor evoked potentials (MEP), whose amplitude is a key proxy for CST integrity [1]. For spTMS-evoked MEP amplitude to be reliable, particularly in clinical populations (e.g., stroke, etc.), its values must be consistent and reproducible [2]. Beyond physiological variability, methodological factors, most notably the inter-pulse interval (IPI), also influence MEP amplitude and variability as demonstrated in healthy individuals.