Reliability of Robotic Transcranial Magnetic Stimulation Motor Mapping.

Robotic Transcranial Magnetic Stimulation (TMS) is a non-invasive and safe tool that produces cortical motor maps using neuronavigation and neuroanatomical images. Motor maps are individualized representations of primary motor cortex (M1) topography that may reflect developmental and interventional plasticity. Results of TMS motor map reliability testing have been variable and robotic measures are undefined. We aimed to determine the short and long-term reliability of robotic TMS motor maps. Twenty healthy participants underwent motor mapping at baseline, 24-hours, and 4-weeks. A 12x12 grid (7mm spacing) was placed over the left M1, centered over the hand-knob area. Four suprathreshold stimulations were delivered at each grid-point. First dorsal interosseous (FDI) motor evoked potentials (MEP) were analyzed offline to generate map characteristics of area, volume, centre of gravity (COG), and hotspot magnitude. Subsets of each outcome corresponding to 75%, 50%, and 25% of each map were determined. Reliability measures including intraclass correlation coefficient (ICC), minimal detectable change (MDC), and standard error of measure (SEM) were calculated. Map volume, COG, and hotspot magnitude were the most reliable measures (good-excellent) over both short- and long-term sessions. Map area reliability was poor-moderate for short- and long-term sessions. Smaller map percentile subsets showed decreased variability but only minimal improvements in reliability. MDC for most outcomes was >50%. Procedures were well tolerated with no serious adverse events. Robotic TMS motor mapping is relatively reliable over time but careful consideration of specific outcomes is required for this method to interrogate plasticity in the human motor system.