In contemporary medicine, few conditions challenge the traditional boundaries between neurology, psychiatry, and rehabilitation as starkly as chronic pain and functional neurological disorders (FND). Despite their distinct diagnostic labels, these conditions inhabit parallel clinical worlds: both involve real, disabling symptoms without clear structural pathology; both have long histories of medical scepticism; and both increasingly demand an integrated, biopsychosocial approach. In this Noijam, Bart van Buchem explores their shared historical roots, overlapping mechanisms, and converging therapeutic strategies.
Historical Perspectives on Pain and Dysfunction
The roots of modern misunderstandings about pain and FND lie deep in the Western medical tradition. From Descartes’ mind-body dualism to the conversion hysteria model of the 19th century, symptoms without visible pathology were often relegated to the realm of the imaginary or the moral. Pain was viewed as a warning system tied to tissue damage, while inexplicable motor or sensory symptoms were seen as hysterical or feigned. These conceptual boundaries marginalised patients, especially women, and contributed to stigma that persists today.
As Vincenot et al. (2025) argue, the meaning and treatment of pain are deeply shaped by cultural metaphors, historical assumptions, and societal values. Similarly, the legacy of Freud’s psychodynamic theories once dominated FND treatment, overshadowing somatic contributions. It was not until the DSM-5 (2013) that FND began to be redefined based on positive neurological signs rather than purely psychological attributions.
Mechanisms of Misfiring: Shared Pathophysiology
Both chronic pain and FND challenge the notion that symptoms must map neatly onto lesions. There is an ongoing debate that describes chronic pain as a disorder of altered predictive processing, where the brain’s expectations alter the interpretation and integration of incoming sensory information. The same framework is increasingly used to understand FND (Edwards, 2012). Here, motor and sensory symptoms are thought to arise from maladaptive top-down predictions that override accurate bottom-up sensory data.
Functional MRI and electrophysiological studies in FND reveal abnormal activity in emotion-processing regions (e.g., amygdala, insula, anterior cingulate cortex) that interact with motor control areas. This pattern mirrors findings in chronic pain patients, where networks involved in salience, interoception, and self-awareness are disrupted. In both conditions, the nervous system is not broken, but it is functioning in a way that is associated with real suffering.
Phenomenology: Subjective Experience and Clinical Overlap
Clinically, patients with chronic pain and those with FND report strikingly similar experiences: fatigue, cognitive fog, dissociation, pain, movement difficulties, and heightened bodily vigilance. These symptoms often fluctuate and worsen under stress, suggesting that attention and emotion play central roles.
Patients with FND frequently show paradoxical symptoms – such as a leg that cannot voluntarily move but does move when distracted – revealing how attention modulates motor output. Chronic pain patients, too, may demonstrate altered protective behaviours and movement strategies based on fear or past experience. Both groups often feel invalidated when clinicians fail to recognise the legitimacy of their symptoms.
Diagnosis: Between Exclusion and Positive Signs
Historically, both FND and chronic pain have been labelled diagnoses of exclusion, leading to uncertainty and therapeutic nihilism. However, this paradigm is shifting. In FND, neurologists are now trained to recognise rule-in signs – such as the Hoover sign or entrainment tests – that reliably distinguish functional symptoms from organic disease. This has improved diagnostic confidence and facilitated earlier intervention.
In chronic pain, diagnosis increasingly relies on clinical expertise and pattern recognition rather than imaging or lab tests. Central sensitisation, for instance, describes a state in which the nervous system becomes hypersensitive without visible damage – again challenging traditional tissue-centric, biomedical models.
Therapeutic Approaches: Education, Retraining, and Meaning
Both chronic pain and FND respond best to treatments that address the whole person. Education is foundational: patients need a coherent, non-blaming explanation of their symptoms that integrates biology and psychology. This reorientation helps reduce fear and fosters engagement in therapy. In FND, physiotherapy focuses on motor retraining using distraction, graded exposure, and functional integration. The goal is not just to regain movement but to shift expectations and restore trust in the body. Similarly, chronic pain treatment employs graded activity, pacing, and cognitive behavioural techniques to reduce fear and re-establish normal movement patterns. Both approaches emphasise therapeutic alliance. Clinicians act not as passive diagnosticians but as coaches who validate the patient’s experience and guide them through recovery. This relational component – empathy, trust, and collaborative goal setting – is often the catalyst for change.
Social and Cultural Dimensions
Stigma remains a shared burden. Patients with FND or chronic pain are often viewed as malingerers or attention-seekers, especially when symptoms do not match biomedical expectations. Language matters: terms like “psychogenic” or “non-organic” may unintentionally reinforce outdated dualisms. Instead, metaphors such as a “software glitch” rather than “hardware damage” may help reframe understanding. Cultural narratives also shape illness behavior. In some societies, expressing distress through physical symptoms is more acceptable than admitting psychological struggle. Clinicians must remain aware of these dynamics and tailor their communication accordingly.
Conclusion: A Shared Future of Integrated Care
Functional neurological disorders and chronic pain syndromes no longer belong in separate silos. They share a clinical territory defined not by structural lesions, but by altered function, expectation, and experience. Emerging neuroscience offers new maps to navigate this terrain – ones that respect the complexity and inseparability of brain-body interactions and the power of meaning in healing.
As we move beyond Cartesian divides, integrated care models that blend neurology, psychology, physiotherapy, and education hold promise. In these parallel worlds, the boundaries are blurring – for the benefit of patients who have waited too long to be believed.
– Bart van Buchem
Clinician, Noigroup Faculty Lead
Director Noigroup European Operations
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