Emergent technologies and applications of TMS and TMS-EEG in clinical neurophysiology for early and differential diagnosis: IFCN handbook chapter.

This chapter examines how emerging neurophysiological technologies are transforming the early and differential diagnosis of neurological disorders. While imaging and fluid biomarkers have greatly advanced the field, they remain limited by cost, invasiveness, and their inability to directly capture dynamic brain activity. Neurophysiological techniques, particularly transcranial magnetic stimulation (TMS) and TMS combined with EEG, offer a unique, non-invasive means of probing cortical excitability, connectivity, and plasticity with millisecond precision. Recent technological and analytical breakthroughs are moving these approaches from research laboratories into clinical practice. By detecting subtle network dysfunctions that precede structural degeneration, they open the possibility of identifying disease in its prodromal or even presymptomatic stages, when interventions may be most effective. This chapter outlines the principles of advanced TMS paradigms and TMS-EEG and explores their application across a range of conditions, including amyotrophic lateral sclerosis, dementias, and movement disorders. It also highlights how integrating neurophysiological measures with blood-based biomarkers and computational tools, such as machine learning, can enhance diagnostic accuracy and guide individualized treatment strategies. Together, these innovations establish neurophysiology as a cornerstone of precision neurology, linking mechanistic insights to clinical decision-making and enabling earlier diagnosis, improved patient stratification, and more targeted therapeutic interventions.