Functional neurological disorder

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

FND sits at the interface of neurology, rehabilitation and mental health but is diagnosed neurologically. The nervous system has intact capacity that is not being accessed normally during particular tasks. Positive bedside signs demonstrate this. In functional leg weakness, power improves during a contralateral automatic task. In gait disorder, balance can improve when walking backwards, running or performing a dual task. These findings are not tricks designed to catch someone out; they reveal mechanism and can become the first treatment demonstration.

Dissociative seizures resemble epileptic seizures but arise through a functional process. The preferred diagnosis is made by an expert from semiology and, where needed, video EEG of the person's typical event. Urinary incontinence, injury and reported tongue biting do not independently prove epilepsy, while a normal interictal EEG cannot exclude it. Some people have both epileptic and dissociative seizures, making event-specific descriptions and recordings essential.

Communication affects outcome. State what the condition is, which positive features support it, that symptoms are real and potentially reversible, and that the patient is not being accused of fabrication. Invite questions and provide a follow-up rather than expecting instant acceptance. Treatment targets retraining, attention, avoidance, pain, sleep, mood and social consequences. Medication treats comorbid conditions, not the core motor mechanism, and unnecessary antiseizure or opioid treatment should be reduced safely after diagnostic review.

Key points

Functional neurological disorder causes genuine motor, sensory, seizure, speech, gait or cognitive symptoms arising from altered nervous-system functioning rather than deliberate production.
Diagnosis is positively supported by internal inconsistency and preserved automatic function, not by normal scans, psychiatric history, unusual affect or failure to find another disease.
Hoover sign shows weak voluntary hip extension that improves when the opposite hip flexes against resistance, demonstrating preserved automatic motor recruitment.
Functional tremor may change frequency, pause with distraction or entrain to a rhythm tapped by another limb, unlike a fixed pathological oscillation.
Dissociative seizures are suggested by variable duration, fluctuating course, closed resistant eyes, asynchronous movement and preserved recall, but no single sign is fully diagnostic.
Video EEG capturing a typical event is the diagnostic gold standard when epilepsy remains uncertain; frontal seizures and syncope can be difficult mimics.
Psychological trauma or stress is neither necessary nor sufficient for diagnosis, although depression, anxiety, PTSD, pain, fatigue and adverse experiences can influence vulnerability and recovery.
FND frequently coexists with migraine, epilepsy, Parkinson disease, multiple sclerosis, neuropathy or structural injury, so clinicians must identify which symptom belongs to which mechanism.
Explain the diagnosis using the demonstrated positive sign, emphasise reversibility and provide a reputable written resource; simply saying tests are normal usually increases uncertainty.
Specialist physiotherapy retrains automatic movement with redirected attention, while occupational, speech, psychological and seizure education address subtype and maintaining factors.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Multifactorial vulnerability

FND can arise from interacting neurobiological, attentional, learning and social factors; psychological trauma is neither necessary nor sufficient for diagnosis.

Physical or neurological precipitant

Injury, migraine, seizure, infection, pain or another neurological illness may focus attention on movement or sensation and precede functional symptoms.

Maintaining factors

Threat monitoring, maladaptive movement strategies, fatigue, pain, avoidance and repeated alarming explanations can perpetuate symptoms after the original precipitant has resolved.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Altered prediction and attention
The brain gives excessive weight to symptom expectations and internally generated predictions while underweighting normal sensory feedback.
2
Disrupted voluntary control
Attention interferes with access to automatic motor, sensory or seizure-regulation processes, creating genuine dysfunction despite preserved underlying pathways.
3
Reinforced symptom networks
Avoidance, repeated checking and inconsistent clinical responses strengthen maladaptive patterns, while distraction and retraining can reveal preserved automatic function.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Hoover sign

Apparent weak hip extension becomes stronger during contralateral resisted hip flexion, showing discrepancy between voluntary and automatic activation.

Functional tremor

Tremor frequency changes with distraction, is suppressed by a ballistic movement or entrains toward an externally imposed tapping rhythm.

Functional gait

Knee buckling occurs without falls, excessive slowness or sway improves with dual task, or walking capacity exceeds formal bed strength.

Functional sensory sign

A sharply demarcated non-anatomical loss or changing boundary can support the diagnosis, but sensory signs alone are less reliable than motor inconsistency.

Dissociative event

A prolonged fluctuating episode with closed eyes and asynchronous movements may suggest dissociative seizure, while injury and cardiorespiratory safety still require attention.

Organic emergency overlapRed flag

Persistent aphasia, true vascular field loss, new sphincter dysfunction, fever or objective progressive neurology requires urgent disease-specific assessment despite known FND.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Positive neurological examinationFirst step
Why
Demonstrate inconsistency and preserved automatic motor capacity.
Interpretation and limitations
Use validated signs such as Hoover, hip-abductor discrepancy, tremor entrainment or distractible gait and explain the finding constructively to the patient.
02
Targeted brain or spinal imaging
Why
Investigate plausible stroke, structural, inflammatory or compressive disease from the acute phenotype.
Interpretation and limitations
Normal imaging does not itself diagnose FND, while an incidental lesion does not automatically explain every symptom; clinical concordance is essential.
03
Video EEG
Why
Capture and classify typical seizure-like events when epilepsy remains possible.
Interpretation and limitations
Absence of epileptic correlate during a habitual event supports dissociative seizure after expert semiology review; some focal seizures have subtle scalp signals.
04
ECG and syncope assessment
Why
Exclude arrhythmic or reflex syncope in collapse or unresponsive episodes.
Interpretation and limitations
Prodrome, posture, pallor, recovery and rhythm data may identify syncope; convulsive movement can occur during cerebral hypoperfusion.
05
Targeted laboratory tests
Why
Identify metabolic, endocrine or medication contributors suggested by presentation.
Interpretation and limitations
Glucose, electrolytes, thyroid, B12, CK or toxicology are chosen from phenotype; extensive repeated testing without a new hypothesis can reinforce disability.
06
Psychiatric and rehabilitation assessment
Why
Identify treatable mood, trauma, pain, fatigue, cognitive and participation factors.
Interpretation and limitations
Comorbidity informs treatment but is not required to validate the neurological diagnosis and should not be framed as its proof.
07
Patient-recorded event video
Why
Provide semiological information when attacks are intermittent and safe recording is possible.
Interpretation and limitations
An expert reviews onset, responsiveness, eyes, movement and recovery; video supplements but does not replace clinical and EEG assessment.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Stroke or demyelinating disease

Objective anatomical deficits and concordant imaging support structural disease, while internal inconsistency and preserved automatic movement support FND; both may coexist.

Epilepsy or syncope

Stereotyped electrical seizures or documented hypoperfusion require different management; capturing a habitual event on video EEG can clarify functional seizures.

Primary movement disorder

Fixed phenomenology, disease-specific examination signs and consistent progression favour dystonia, tremor or parkinsonism over a functionally variable motor pattern.

Factitious disorder or malingering

FND symptoms are involuntary and should not be equated with deliberate fabrication or external-gain behaviour, which require separate positive evidence.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Acute presentationExclude emergency then seek positive signsFirst stepNew weakness, abnormal movement, gait or seizure-like activity presents urgently.

1Use the standard stroke, seizure, cord, metabolic or injury assessment appropriate to onset and objective findings, without allowing a previous FND label to lower safety.
2Once immediate threats are addressed, test validated inconsistency signs and document exactly what changes with automatic movement, distraction or entrainment.
3Seek neurological review when diagnosis remains uncertain or organic and functional components may coexist, avoiding repeated non-directed emergency investigations.

02Diagnostic explanationUse the examination as the first treatmentPositive findings support FND and important structural alternatives are addressed.

1Name functional neurological disorder clearly, affirm that symptoms are genuine and explain a software or access problem without implying damaged nerves or fabrication.
2Demonstrate the positive sign, such as improved automatic hip power, and connect preserved capacity to the possibility of retraining and recovery.
3Provide written information, allow uncertainty and arrange follow-up, recognising that a rushed one-off explanation may be experienced as rejection.

03RehabilitationRetrain automatic functionMotor, gait, sensory, speech or fatigue symptoms impair daily participation.

1Use FND-informed physiotherapy that redirects attention away from the affected movement, builds automatic patterns and avoids reinforcement through repeated manual strength testing.
2Add occupational therapy for routines, pacing and return to roles, speech therapy for voice or swallow symptoms and psychology for relevant attention, trauma or avoidance mechanisms.
3Treat migraine, pain, sleep, depression and anxiety while setting functional goals and a relapse self-management plan rather than requiring complete symptom disappearance first.

04Dissociative seizuresCreate a safe event-specific planTypical events are confirmed as functional or dissociative rather than epileptic.

1Explain the event diagnosis using video EEG or positive semiology and distinguish any coexisting epileptic seizure types in writing for patient, family and emergency services.
2Teach carers to protect from injury, time the event, reduce stimulation and avoid painful stimuli, restraint or repeated emergency medication unless the event differs or safety changes.
3Review antiseizure medicines with neurology and taper only when epilepsy is excluded, while applying current DVLA guidance and addressing attack triggers through therapy.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Clarifies that education and subtype-specific rehabilitation are active treatment rather than an absence of care.

No core FND medicine

There is no medicine dose that directly corrects functional motor or seizure mechanisms; prescribe only for a defined comorbid symptom or diagnosis.

Avoid escalating opioids, sedatives or antiseizure drugs for unconfirmed mechanisms; every continued medicine needs a target, benefit review and safe withdrawal plan.

Removes unnecessary adverse effects and reinforces the correct event mechanism when coexisting epilepsy has been excluded.

Antiseizure medicine review

When video EEG confirms only dissociative seizures, neurology designs a gradual agent-specific taper using the BNF rather than abrupt cessation.

Some patients have both event types; abrupt withdrawal can provoke epileptic seizures, and driving advice must be based on all attacks and current DVLA rules.

Treats depression, anxiety or PTSD that may worsen disability but is not a specific cure for FND.

Antidepressant for comorbidity

Select and titrate an SSRI or other agent under the relevant NICE depression or anxiety guideline when a separate treatable disorder is diagnosed.

Explain the indication to avoid implying symptoms are imaginary; review suicidality, activation, interactions, discontinuation and individual response.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Iatrogenic injury

Repeated emergency sedation, unnecessary surgery, antiseizure medicines and invasive testing can cause direct harm when functional symptoms are mistaken for structural disease.

Disability and deconditioning

Weakness, gait disorder and attack-related avoidance can lead to falls, loss of work, muscle wasting and increasing dependence despite reversible motor capacity.

Comorbid illness being missed

Diagnostic overshadowing may obscure migraine, epilepsy, neuropathy or other genuine disease because all new symptoms are incorrectly attributed to FND.

Stigma and treatment disengagement

Dismissive explanations damage trust and reinforce uncertainty, reducing participation in physiotherapy, psychological care and self-management that could improve function.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Track walking, self-care, work, study and attack-related restriction rather than repeatedly scoring symptom intensity without functional context.
Revisit positive examination signs to demonstrate emerging automatic control, using them collaboratively rather than as tests of honesty.
Maintain vigilance for new objective neurological signs and investigate a genuinely new phenotype on its merits, including in established FND.
For dissociative seizures record frequency, duration, injury, emergency treatment and distinct epileptic events, refining the safety plan from actual patterns.
Review medicine burden, especially opioids, benzodiazepines and antiseizure drugs, reducing only with diagnosis-specific supervision.
Assess mood, trauma symptoms, pain, fatigue, sleep, social stress, safeguarding and carer burden without making psychological disclosure a condition of treatment.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Inconsistency is positive

A reproducible improvement during automatic movement demonstrates intact capacity and supports a functional mechanism more strongly than a list of normal scans.

Attention alters movement

Distractibility and entrainment reflect abnormal allocation of attention and motor prediction, providing both diagnostic evidence and a rehabilitation strategy.

Stress is not required

Some patients identify trauma or stress and others do not; withholding diagnosis until a psychological cause is found is inaccurate and stigmatising.

Comorbidity is common

A person can have epilepsy and dissociative seizures or multiple sclerosis and functional weakness, requiring symptom-by-symptom formulation.

Explanation changes prognosis

A clear rule-in diagnosis with demonstration and follow-up creates a therapeutic bridge, whereas dismissal after normal testing entrenches uncertainty.

11Common pitfallsFrequent interpretation and management errors.

01
Diagnosing FND solely because imaging is normal.
02
Assuming symptoms are consciously produced or attention seeking.
03
Requiring a trauma history before making a positive diagnosis.
04
Using previous FND to dismiss a new stroke or cord syndrome.
05
Calling every non-convulsive EEG a dissociative seizure without capturing an event.
06
Stopping antiseizure medicine abruptly when epilepsy may coexist.
07
Offering reassurance without specialist rehabilitation or follow-up.