Predictors of 30-Day Healthcare Utilization After Telemedicine Management of Minimal Traumatic Intracranial Hemorrhage.

The resting motor threshold (RMT) is a fundamental measurement in transcranial magnetic stimulation (TMS) studies and is defined as the lowest stimulus intensity capable of evoking MEPs with a peak-to-peak amplitude greater than 50 µV in at least 5 out of 10 consecutive TMS pulses, while the target muscle was completely relaxed. The RMT reflects the transsynaptic activation of corticospinal neurons, as it can be modulated by changing the conductivity of presynaptic sodium or calcium channels. The RMT is commonly used as an indicator of corticospinal tract (CST) excitability and as a basic dosing unit for TMS-based therapeutic interventions. Interindividual variability in the RMT is well known, reflecting the differences in CST excitability among individuals at baseline and the individual differences in the brain’s sensitivity to TMS. Owing to significant differences in brain anatomy among individuals, researchers first speculated that variations in brain structural characteristics might cause individual differences in the RMT. A stable positive correlation was found between the distance from the coil to the cerebral cortex and RMT. List et al. found cortical thickness of the hand knob of the primary motor cortex was a significant positive predictor of RMT, independent of coil-to-cortex distance. Klöppel et al. reported a linear inverse relationship between the RMT and large bihemispheric clusters and fractional anisotropy in areas such as the primary motor area, premotor area, white matter under the posterior prefrontal cortex, internal capsular knee, cerebral infarction, and corpus callosum. Mirchandani et al. also reported an association between the anisotropy value and the RMT. Rosso et al. reported that the RMT is inversely correlated with the dominant hemisphere gray matter volume. In addition, studies have shown that RMT is also influenced by factors such as age and coil orientation. RMT increases with age, and a smaller RMT is obtained when the coil current is placed perpendicular to the central sulcus. In the resting state, brain functions and connections between brain regions have individual-specific “fingerprints” that capture a wide range of interindividual differences in social, cognitive, and behavioral tendencies and the brain response to external stimuli. Therefore, the interindividual differences in RMT might be accounted for by individual-specific brain functional characteristics at baseline. Rosso et al. reported that the RMT was inversely correlated with the functional connectivity between the premotor area and M1. However, Engelhardt et al. replicated Rosso et al.’s research and obtained contradictory results. This discrepancy highlights the complexity of the relationship. The influence of brain functional characteristics on the interindividual variability in RMT remains understudied.