Overview
Functional Neurological Disorder (FND)
1. Clinical Overview
Summary
Functional Neurological Disorder (FND) is characterised by neurological symptoms (weakness, movement disorders, seizures, sensory changes) that are incompatible with recognised neurological or medical conditions. These are real, involuntary symptoms - NOT feigned. FND is now understood as a "software" rather than "hardware" problem.
Key Facts
| Aspect | Detail |
|---|---|
| Definition | Neurological symptoms incompatible with organic disease |
| Key Concept | Real symptoms, not faking or malingering |
| Common Presentations | Weakness, seizures, tremor, sensory loss |
| Diagnostic Approach | Made on positive signs, not just exclusion |
| Treatment | Physiotherapy, psychology, explanation |
Clinical Pearls
- Hoover's Sign: Weakness in hip extension improves when flexing contralateral hip (pathognomonic)
- FND is a positive diagnosis: Made on clinical signs, not exclusion
- Common AND disabling: Second most common neurology outpatient presentation
- Comorbidity: FND can coexist with organic neurological disease
2. Epidemiology
Prevalence
| Population | Prevalence |
|---|---|
| Neurology clinics | Second most common diagnosis |
| Emergency departments | 20-30% of "seizures" are PNES |
| General population | 50 per 100,000 |
Demographics
| Factor | Association |
|---|---|
| Sex | Female > Male (3:1) |
| Age | Any age, peak young-middle adults |
| Education | No clear association |
| Psychological history | Often present (but not required) |
3. Pathophysiology
Modern Understanding
Abnormal Predictive Processing
(Brain predicts abnormal movement/sensation)
↓
Attention/Expectation Amplification
↓
Autonomous Nervous System Execution
(Bypasses voluntary control)
↓
REAL INVOLUNTARY SYMPTOMS
↓
Maintained by Learned Brain Patterns
Key Concepts
| Concept | Explanation |
|---|---|
| Predictive coding | Brain's prediction overrides sensory input |
| Attention | Symptom focus amplifies presentation |
| Dissociation | Disconnection of voluntary control |
| NOT malingering | Symptoms are involuntary |
4. Clinical Presentation
Functional Weakness
| Feature | Description |
|---|---|
| Hoover's sign | Hip extension weakness recovers with contralateral hip flexion |
| Drift without pronation | Arm drifts down without pronating |
| Co-contraction | Simultaneous agonist/antagonist activation |
| Give-way weakness | Initial strength then sudden collapse |
| Inconsistency | Differs with distraction |
Functional (Dissociative) Seizures
| Feature | FND Seizures | Epileptic Seizures |
|---|---|---|
| Eyes | Closed | Open |
| Movements | Asynchronous, variable | Stereotyped, rhythmic |
| Pelvic thrusting | Common | Rare (except frontal) |
| Duration | Often prolonged (> min) | Usually <3 min |
| Recovery | Rapid | Post-ictal confusion |
| Tongue bite | Tip (if any) | Lateral |
| Injury | Less common | Common |
Other Presentations
| Type | Features |
|---|---|
| Functional tremor | Variable frequency, distractible, entrainment |
| Functional sensory loss | Non-anatomical distribution |
| Functional dystonia | Fixed postures, variable |
| Functional gait | Bizarre, effortful, lurching |
5. Clinical Examination
Positive Signs (Make the Diagnosis)
| Sign | Test |
|---|---|
| Hoover's | Weakness reverses with contralateral hip flexion |
| Hip abduction | Weakness improves with contralateral testing |
| Tremor entrainment | Matches examiner's tapping rhythm |
| Distractibility | Symptoms disappear when distracted |
| Inconsistency | Performance differs vs observation |
Important Principles
- Make a positive diagnosis based on signs
- Do NOT assume FND just because tests are negative
- Consider comorbid organic disease
6. Investigations
Approach
| Purpose | Test |
|---|---|
| Rule out organic | MRI brain/spine if indicated |
| Confirm FND | Video EEG for seizures (gold standard for PNES) |
| Baseline | Blood tests rarely helpful |
Key Point
- FND is NOT a diagnosis of exclusion
- Investigations should be targeted, not exhaustive
7. Management
Core Principles
| Principle | Action |
|---|---|
| Explanation | Clear, empathic delivery - crucial |
| Validate | Symptoms are real |
| Name it | "Functional Neurological Disorder" |
| Reversibility | Emphasise potential for improvement |
How to Explain
- "Your brain is not damaged, but it's not working properly"
- "Like a software glitch on a computer - the hardware is fine"
- "Your nervous system is sending the wrong signals"
- Recommend neurosymptoms.org
Multidisciplinary Treatment
| Component | Role |
|---|---|
| Physiotherapy | Movement retraining, distraction techniques |
| Psychology | CBT, especially for functional seizures |
| Occupational therapy | Function and activity |
| Speech therapy | If swallowing/speech affected |
Evidence-Based Interventions
- Physiotherapy: Specific FND-focused protocols effective
- CBT for seizures: Good evidence (CODES trial)
- SSRI: For comorbid depression/anxiety
8. Complications
| Complication | Notes |
|---|---|
| Disability | Can be very disabling |
| Iatrogenic harm | Unnecessary investigations/procedures |
| Delayed diagnosis | Stigma leads to underdiagnosis |
| Comorbid mood disorder | Depression, anxiety common |
| Healthcare seeking | Frequent ED presentations |
9. Prognosis & Outcomes
| Factor | Outcome |
|---|---|
| Early diagnosis + explanation | Better prognosis |
| Longer duration before diagnosis | Worse prognosis |
| Functional seizures | Good response to CBT |
| Comorbid psychiatric illness | May complicate recovery |
| Overall | Variable - some recover fully, some chronic |
10. Evidence & Guidelines
| Organisation | Key Points |
|---|---|
| ABN | Positive diagnosis, multidisciplinary care |
| CODES Trial | CBT effective for functional seizures |
| neurosymptoms.org | Patient resource (Jon Stone) |
11. Patient / Layperson Explanation
What is FND? FND is when your nervous system isn't working properly, but there's no damage to the brain or nerves. Your symptoms are real and involuntary - you are NOT making them up or imagining them.
What causes it? Think of it like a software problem rather than hardware damage. Your brain is sending the wrong signals to your body. We don't fully understand why this happens, but it's common and treatable.
Is it "all in my head"? Your symptoms are real. They are caused by a genuine problem with how your nervous system is functioning. This is not a sign of weakness or a psychiatric illness, though stress can sometimes make it worse.
How is it treated?
- Understanding your diagnosis is the first step
- Specialist physiotherapy can help retrain your movements
- Psychology (like CBT) is helpful, especially for seizures
- Most people improve with time and the right support
Where can I learn more? Visit www.neurosymptoms.org - an excellent resource written by specialists.
12. References
- Stone J. Functional Neurological Disorder. Lancet Neurology. 2016;15:1138-1148.
- Goldstein LH, et al. CBT for psychogenic nonepileptic seizures (CODES). JAMA Neurology. 2020.
- Nielsen G, et al. Physiotherapy for FND. J Neurol Neurosurg Psychiatry. 2015.
- neurosymptoms.org (Patient Information).