Definition and DSM-5 criteria
Functional neurological symptom disorder (FND; conversion disorder) is a disorder of altered voluntary motor or sensory function that is internally inconsistent and incompatible with recognised neurological disease, yet is genuinely involuntary — not feigned. The DSM-5 reframing was significant: the diagnosis is now made on positive clinical findings of incompatibility, and it no longer requires an identifiable psychological stressor nor that feigning be disproven.
The DSM-5 criteria are:
- Criterion A — one or more symptoms of altered voluntary motor or sensory function.
- Criterion B — clinical findings provide evidence of incompatibility between the symptom and recognised neurological or medical conditions (this is the rule-in step).
- Criterion C — the symptom or deficit is not better explained by another medical or mental disorder.
- Criterion D — the symptom causes clinically significant distress or impairment, or warrants medical evaluation.
Specify the symptom type (weakness/paralysis, abnormal movement, swallowing/speech symptoms, attacks/seizures, sensory loss, special-sensory or mixed) and acute vs persistent, with/without psychological stressor.
Clinical features
Common paediatric presentations are functional (dissociative non-epileptic) seizures, functional weakness or gait disorder, tremor and other abnormal movements, sensory loss, and visual or speech disturbance. Onset may be abrupt, sometimes after a physical injury, illness or stressor — though a stressor is not required. Symptoms fluctuate, are distractible, and are inconsistent over time. The child is genuinely impaired; la belle indifférence is unreliable and should not be used to diagnose.
Diagnosis
FND is a positive, rule-in diagnosis based on demonstrating internal inconsistency, not a diagnosis of exclusion. Key bedside signs include Hoover’s sign (functional leg weakness), the tremor entrainment test, a positive drift-without-pronation test, give-way weakness, tubular/non-anatomical sensory loss, and, for functional seizures, features such as preserved awareness, side-to-side head movement, prolonged duration, eye closure and the absence of a post-ictal rise in prolactin (EEG-video where available). Explain these positive signs to the family — they make the diagnosis credible and treatable.
See the full criteria: Functional Neurologic Symptom Disorder
Red flags
- Features that fit a recognised neurological disease (consistent, non-distractible deficit; fixed visual-field defect; pathological reflexes)
- Reduced consciousness, fever, or signs of raised intracranial pressure
- Acute focal deficit where stroke or demyelination is plausible — investigate
- Progressive, fixed deficit rather than the fluctuating, distractible pattern of FND
- Remember dual pathology — FND can coexist with organic disease (e.g. functional and epileptic seizures together)
Management overview
The foundation is a clear, positive, validating explanation: the symptoms are real and involuntary, the nervous system is malfunctioning (a software, not hardware, problem), and the condition is reversible. Never say “there is nothing wrong” or imply the child is faking — this predicts poor outcome and rupture. Show the patient their own positive signs (e.g. Hoover’s) to make the diagnosis tangible and hopeful.
Management is multidisciplinary and rehabilitative: physiotherapy for functional motor and gait symptoms, occupational therapy, and psychological therapy (CBT and stress-system work) where relevant — but therapy proceeds whether or not a stressor is found. Treat comorbid anxiety, depression or trauma. A coordinated team, consistent messaging across clinicians, return-to-school planning, and family engagement are central; mixed or covert messages undermine recovery. Paediatric FND, addressed early with a confident positive diagnosis, often has a good prognosis.
References
- American Psychiatric Association. DSM-5-TR. 2022.
- Stone J, Carson A. Functional neurologic disorders. Continuum. 2015;21(3):818–837.
- Kozlowska K, et al. Functional somatic symptoms in children and adolescents. 2020.
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.