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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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
Positive bedside and diagnostic signs that 'rule in' functional neurologic disorder — conversion is no longer a diagnosis of exclusion.
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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