Functional neurological disorder and other unexplained syndromes

Abstract

Functional neurological disorder is a syndrome of medically unexplained neurological symptoms. In The Lancet Neurology, Mark Hallett and colleagues review some of the potential explanations for functional neurological disorder and the evidence that supports these explanations. 1 Hallett M Aybek S Dworetzky B McWhirter L Staab J Stone J Functional neurological disorder: new phenotypes, common mechanisms. Lancet Neurol. 2022; (published online April 14.)https://doi.org/10.1016/S1474-4422(21)00422-1 Summary Full Text Full Text PDF PubMed Scopus (1) Google Scholar The paper by Hallett and colleagues, however, is more than a Review: it is also a territorial claim, seeking to expand the boundaries of what should be considered functional neurological disorder. The details of this claim are unlikely to be controversial to any clinician working in the field: the presentations Hallett and colleagues describe are not new, even if they do not fall within the current classifications of the disorder. But the claim is nonetheless remarkable, as even a decade ago it would have been thought to be sheer folly. A good argument could then have been made that functional neurological disorder (or conversion disorder, as it was more formally known) was the most stigmatised of all disorders, even compared with other unexplained syndromes. What would have been the point of expanding the scope of a diagnosis that patients went to such lengths to avoid? 2 Crimlisk HL Bhatia KP Cope H David AS Marsden D Ron MA Patterns of referral in patients with medically unexplained motor symptoms. J Psychosom Res. 2000; 49: 217-219 Crossref PubMed Scopus (35) Google Scholar The expansive mood in the Review by Hallett and colleagues therefore reflects a striking transformation in the status of functional neurological disorder. Functional neurological disorder has become a diagnosis that a neurologist might be comfortable to give, and that a patient might be glad to receive. Functional neurological disorder: new subtypes and shared mechanismsFunctional neurological disorder is common in neurological practice. A new approach to the positive diagnosis of this disorder focuses on recognisable patterns of genuinely experienced symptoms and signs that show variability within the same task and between different tasks over time. Psychological stressors are common risk factors for functional neurological disorder, but are often absent. Four entities—functional seizures, functional movement disorders, persistent perceptual postural dizziness, and functional cognitive disorder—show similarities in aetiology and pathophysiology and are variants of a disorder at the interface between neurology and psychiatry. Full-Text PDF