Conversion Disorder (Functional Neurological Symptom Disorder)
Neurologic symptoms (motor, sensory, seizure-like) incompatible with recognized neurologic disease.
Also known as: FND, functional neurologic disorder, conversion disorder, PNES, nonepileptic seizures
Overview
DSM-5-TR: ≥1 symptom of altered voluntary motor or sensory function (weakness, abnormal movements, sensory loss, speech symptoms, swallowing, seizure-like episodes); clinical findings provide evidence of incompatibility between the symptom and recognized neurologic or medical conditions; symptom not better explained by another disorder; causes distress or impairment. Diagnosis is a 'rule-IN' diagnosis based on positive signs of incompatibility, not merely absence of disease.
Epidemiology
Incidence ~4-12 per 100,000/year; prevalence in neurology outpatient clinics ~5-15%. Female:male ~2-3:1. Onset typically adolescence to mid-40s. Often co-occurs with depression, anxiety, PTSD, and other functional somatic syndromes.
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Risk factors
- Female sex
- History of childhood adversity or trauma (especially sexual abuse)
- Comorbid mood, anxiety, dissociative, or personality disorders
- Recent psychosocial stressor or physical injury
- Other functional somatic syndrome (IBS, fibromyalgia, chronic fatigue)
- Family member with neurologic illness (modeling)
Pathophysiology
Disruption of normal sensorimotor integration without structural lesion. Altered attention to body, abnormal sense of agency, and impaired top-down inhibition of motor/sensory areas. fMRI studies show abnormal activity in temporoparietal junction and reduced sense of self-agency. Symptoms are NOT consciously produced (differs from factitious disorder).
Clinical presentation
Symptoms
- Motor: limb weakness or paralysis, tremor, abnormal gait, dystonia
- Sensory: anesthesia or paresthesia in nonanatomic distribution
- Special sensory: blindness, deafness, diplopia
- Speech: dysphonia, dysarthria, mutism
- Seizure-like: nonepileptic attacks with retained awareness, asynchronous limb movement, eyes closed, side-to-side head shaking
- Swallowing: globus, dysphagia
Signs / physical exam
- Positive 'rule-in' signs of functional neurology — diagnosis should rest on these, not absence of other findings
- Hoover sign (functional leg weakness): hip extension weak on direct testing but normal during contralateral hip flexion against resistance
- Tremor entrainment test: functional tremor matches the frequency of voluntary tapping the patient is asked to perform with the contralateral hand
- Drift without pronation in functional arm weakness
- Closed eyes during PNES; eyes typically open in epileptic seizure
- Nonanatomic sensory loss (e.g., midline split exactly at the body midline)
- La belle indifférence (lack of concern) is unreliable and no longer a required criterion
Differential diagnosis
- True neurologic disease — Multiple sclerosis, stroke, epilepsy, Guillain-Barré — workup as clinically indicated; remember conversion and organic disease can coexist
- Factitious disorder — Intentional symptom production for sick role
- Malingering — Intentional symptom production for external incentive
- Somatic symptom disorder — Disproportionate response to symptoms — may be medically explained or not; conversion has specific neurologic incompatibility
- Psychogenic nonepileptic seizures (PNES) — A subtype of conversion disorder — video EEG is gold standard
- Dissociative disorders — Disruptions of consciousness/identity/memory rather than motor/sensory
Diagnostic workup
Diagnostic criteria
DSM-5-TR: ≥1 altered motor/sensory symptom; clinical findings show incompatibility with known disease (positive signs); not better explained otherwise; impairment/distress. Specify acute (<6 mo) vs persistent (>6 mo); with vs without psychological stressor.
Labs
- Targeted to exclude mimics — TSH, CMP, glucose, B12, autoimmune panel as indicated
Imaging
- MRI brain/spine if focal neurologic symptoms
- Video EEG — gold standard for PNES; captures event and confirms absence of epileptiform discharge
- Nerve conduction/EMG if peripheral weakness or sensory loss
- Avoid open-ended scanning that prolongs uncertainty
Diagnostic algorithm
| Sign / Test | Symptom assessed | Functional finding |
|---|---|---|
| Hoover sign | Leg weakness | Hip extension weak on direct test, normal with contralateral hip flexion |
| Tremor entrainment | Tremor | Tremor adopts the frequency of voluntary contralateral tapping |
| Drift without pronation | Arm weakness | Arm drifts downward without forearm pronation (organic weakness pronates) |
| Closed-eyes seizure | Seizure-like episode | Eyes forcefully closed throughout (epileptic seizures usually open) |
| Midline sensory split | Sensory loss | Sensory loss splits exactly at midline (organic loss spares vibration across bony midline) |
| Video EEG | PNES vs epilepsy | Captures event without epileptiform discharge |
Treatment
First-line
- Clear, confident communication of the diagnosis using positive signs — explain it as a 'software, not hardware' problem; do NOT frame as 'no disease found'
- Physical therapy / occupational therapy for motor symptoms — neurorehabilitation tailored to FND
- Cognitive behavioral therapy, especially for PNES
- Treat comorbid depression, anxiety, PTSD
Second-line / adjunct
- Speech therapy for functional speech/swallowing
- Multidisciplinary inpatient rehabilitation for refractory cases
- Transcranial magnetic stimulation (emerging evidence)
Complications
- Iatrogenic harm from repeated procedures, including misadministered anticonvulsants and intubations for PNES
- Disability, employment loss
- Depression and suicidal ideation
- Chronicity if diagnosis delayed >12 months
PANCE pearls
- Conversion disorder is a positive diagnosis based on incompatibility signs, not a diagnosis of exclusion.
- Hoover sign and tremor entrainment are high-yield bedside tests on exam questions.
- PNES is treated with CBT, NOT antiepileptics; misdiagnosis as epilepsy averages 7 years.
- Symptom onset often follows a stressor, but a stressor is no longer required for diagnosis.
- How the diagnosis is delivered determines outcome — confident, validating explanation predicts symptom improvement.
References
- DSM-5-TR — American Psychiatric Association. DSM-5-TR. 2022.
- Stone 2015 — Stone J, Carson A. Functional Neurologic Disorders. Continuum (Minneap Minn) 2015;21:818-37.
- Espay 2018 — Espay AJ et al. Current Concepts in Diagnosis and Treatment of Functional Neurological Disorders. JAMA Neurol 2018;75:1132-1141.
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