{
  "abstract": "Background Functional neurological disorder (FND) is a complex neuropsychiatric condition characterized by neurological symptoms without structural neuropathology. Its aetiology likely involves interactions between psychosocial and biological factors, potentially linked to circuit-level brain dysfunction. While neurophysiological techniques such as electroencephalography (EEG), electromyography (EMG), and evoked potentials (EPs) hold promise for elucidating FND pathophysiology, existing studies are often limited by small sample sizes and inconsistent findings. This systematic review synthesizes current neurophysiological evidence, explores potential biomarkers, and proposes future research directions.Methods We conducted a systematic search of MEDLINE, Embase, and PsycINFO databases, complemented by manual searches. Eligible studies included participants with any FND subtype, used neurophysiological measures, and reported sufficient data. Exclusions were studies with fewer than five FND participants or non-English publications. Quality assessment employed the Newcastle-Ottawa Scale. Narrative synthesis summarized findings due to study heterogeneity, precluding meta-analysis. This review was registered on PROSPERO, CRD42022226274.Results From 20,944 identified abstracts, 150 studies met inclusion criteria, involving 9,556 participants (4,207 with FND). The most common study designs were 88 case-control studies, followed by 39 case series, 18 cross-sectional studies, and 5 cohort studies. Functional seizures were the most studied symptom, with video-EEG revealing normal EEG patterns during episodes, aiding diagnostic differentiation. Resting EEG highlighted reduced connectivity between brain regions, though overreads of sharply contoured rhythms or fragmented alpha activity were reported. For functional movement disorders (e.g., tremor, myoclonus, dystonia), EMG revealed hallmark features like variability, distractibility, and entrainment. Notably, functional tremor showed reduced frequency during ballistic movements and increased amplitude under weight loading. EEG studies in functional myoclonus identified Bereitschaftspotential, suggesting motor preparation. Functional weakness exhibited normal motor units but reduced interference patterns on EMG. EPs in sensory symptoms, such as anaesthesia, were predominantly normal but occasionally revealed inconsistencies.Conclusions This review identifies distinct neurophysiological profiles associated with FND, enhancing our understanding of its mechanisms and offering potential diagnostic utility. These findings underscore the importance of integrating neurophysiological assessments into clinical practice and provide a foundation for advancing FND research.",
  "authors": [
    {
      "affiliations": [
        "Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK"
      ],
      "name": "Daruj Aniwattanapong"
    },
    {
      "affiliations": [
        "Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK"
      ],
      "name": "Timothy R Nicholson"
    }
  ],
  "title": "#8217 Systematic review of the neurophysiology of functional neurological disorder",
  "uid": "7455f7e6-a0be-5dfc-baa9-a96412b65793"
}