Mark Hallett and the renaissance of functional neurological disorder

This article traces the contributions of Mark Hallett (1943-2025) to Functional Neurological Disorder (FND) from 2003 to his death. Mark brought his expertise in motor physiology, free will, volition and agency to this neglected but common condition. He raised awareness of our need to understand its pathophysiology, natural history and treatment, and then became a key researcher investigating abnormalities of brain networks found in individuals with the condition, as well as its multifactorial aetiology. He played a pivotal role in organising international meetings and books on functional movement disorder and FND, culminating in his role as the first president of the International FND Society (2019-2022). In 2024, Mark Hallett gave the 2024 American Academy of Neurology Wartenberg lecture, recalling "la lésion dynamique" proposed by Charcot as the pathophysiology of FND in the 19th century. This lecture was emblematic of the renaissance of interest in FND after a long period of neglect and his huge contribution to our understanding of the disorder.