Mastering Functional Neurological Disorder for MRCP PACES

Few patients expose a candidate's true level like the patient with functional neurological disorder (FND). You might meet them dragging a 'useless' leg around an examination station, shaking so hard the chair rattles, or describing blackouts that no tablet has ever touched. However they arrive, they are testing the same three things: can you make a positive clinical diagnosis, can you explain it without offending the patient, and can you investigate and manage safely? Get those right and you present like a registrar. Say 'it's all in your mind' and no amount of immaculate neuroanatomy rescues the station.

1. Why Examiners Love FND

• It is genuinely common. FND is one of the most frequent reasons for referral to a general neurology clinic, and dissociative (non-epileptic) attacks account for a substantial proportion of patients attending epilepsy services — roughly one in five in most series.

• The diagnosis rests on positive signs, not on excluding every disease known to humankind. Examiners want to see you rule it in.

• It tests communication at consultant level — delivering a diagnosis the patient may have waited years, and several failed treatments, to hear.

• It tests rational investigation — knowing what to exclude, and just as importantly, when to stop.

• It exposes unhelpful language instantly. One dismissive phrase and the communication domain collapses.

2. What FND Is — and What It Is Not

Definition: genuine, involuntary neurological symptoms whose clinical features are internally inconsistent or incongruent with recognised neurological disease. In DSM-5 it appears as functional neurological symptom disorder (conversion disorder).

Five truths to carry into the station:

1. It is a positive diagnosis, not a diagnosis of exclusion. You identify signs that actively generate the symptoms.

2. A psychological precipitant is not required for diagnosis — a deliberate change from older teaching. Many patients have none.

3. It is not malingering (conscious fabrication for external gain), not factitious disorder (conscious production to occupy the sick role), and not imagined.

4. It coexists with organic disease alarmingly often — around one in ten patients with dissociative attacks also has epilepsy.

5. Normal tone, reflexes and plantars with dramatic weakness should make you think 'functional first, verify second'.

Update your vocabulary

3. The Positive Signs That Clinch the Diagnosis

Motor — weakness

• Hoover's sign — the sign that pays the mortgage. With the patient supine, cup your palm under the 'weak' heel and ask them to press down (hip extension) — it is weak. Then ask them to lift the other leg (hip flexion) against your resistance — and you feel the previously weak heel press firmly into your palm. The weakness resolves when the contralateral associated movement is performed, because hip extension is reflexively reinforced by opposite hip flexion. Organic pyramidal weakness abolishes that association.

• Hip abductor sign — identical logic in the coronal plane: abducting one leg against resistance restores abduction of the 'weak' other.

• Give-way weakness — power that is briefly normal then collapses; effort that fatigues instantaneously rather than gradually.

• Drift without fall — the outstretched arm wanders and hovers but never crashes; the patient remains in control of the 'paralysis'.

• Functional dystonia — a foot fixed in inversion and plantarflexion, often painful and stable from the outset.

Movement — tremor

• Entrainment and distractibility — ask the patient to tap a rhythm with the unaffected hand; a functional tremor will adopt the tapping rhythm, change character, or stop altogether.

• The load sign — weighting the trembling limb increases functional tremor amplitude, whereas an organic tremor (classically Parkinson's) suppresses.

Gait

• Dragging gait — a monoparetic-looking leg hauled from the hip, often held in internal rotation.

• Knee buckling without falling — dramatic buckling episodes in which the patient never actually hits the ground.

• 'Walking on ice' — exaggerated slowness and caution disproportionate to any deficit found on the couch.

Sensory

• Midline split hemisensory loss — sensation sharply guillotined at the midline, including face and trunk; vibration 'switches off' the moment the tuning fork crosses the midline of the sternum. Organic sensory loss blends and rarely aligns face and body on one geometric line.

• Non-dermatonal patchy numbness that defies any peripheral nerve or root map.

Attacks — dissociative (non-epileptic) seizures

• Eyes closed, often with resistance to passive eye opening (organic ictal eyes are usually open).

• Prolonged, fluctuating events with asynchronous jerking, pelvic thrusting, opisthotonic arching or head rolling.

• Lateral tongue biting and significant self-injury are less common than in epilepsy.

• Distress, crying and variable recall afterwards; events often occur in waiting rooms and clinics rather than from sleep.

• Investigation of choice: video-EEG telemetry with a recorded attack where diagnosis is uncertain.

Vision

• Tubular (tunnel) fields — the constricted field fails to widen as you move the target further away on confrontation.

Red flags — pause and investigate first

• A new, fixed or progressive deficit; genuine pyramidal signs (spastic tone, brisk reflexes, upgoing plantars)

• Sphincter dysfunction or a sensory level (think cord compression — a never-miss diagnosis)

• Fever, headache, neck stiffness, immunosuppression, or recent neurosurgery

• Sudden onset in a patient with vascular risk factors; new medication or toxin exposure

4. The Two-Way Rule

Functional and organic diagnoses are not mutually exclusive. The patient can have multiple sclerosis and functional overlay; diabetic neuropathy and functional numbness; epilepsy and dissociative attacks. A normal MRI does not make symptoms functional, and an abnormal MRI does not make them organic — a small incidental white matter lesion in a 30-year-old with entrainable tremor means nothing. Diagnosing FND does not switch off your suspicion for disease; it runs in parallel with it.

5. Where FND Appears in PACES

In the examination stations

The classic scenario: a young or middle-aged adult, one dramatic limb, and a nervous system that is otherwise textbook normal. Demonstrate Hoover's sign with practised choreography — hand under the heel, contralateral flexion against resistance — and present fluently:

'This is a 34-year-old with a two-year history of left leg weakness. There was no wasting, normal tone, symmetrical reflexes and downgoing plantars. Power showed give-way weakness of left hip extension which returned to full strength on Hoover's testing, when the right hip flexed against resistance. Gait was dragging in character without neurological posturing. My leading diagnosis is functional weakness — a functional neurological disorder — on the basis of positive signs with an otherwise normal neurological examination. I would exclude structural disease with appropriate imaging, explain the diagnosis positively, and refer for specialist neuro-physiotherapy.'

In the consultation stations

The scenario bank examiners draw from:

• The new diagnosis — a 'shaky hand' or 'weak leg' referred after 'all the tests came back normal'; your task is to explain.

• The review consultation — blackouts persisting despite two antiepileptics; the patient asks why the tablets 'aren't working'. Time to raise dissociative attacks.

• The angry patient — 'The GP said it was all in my head.' Your task is to rebuild trust and reframe the diagnosis.

• The medication decision — a patient with established NEAD asks to stop carbamazepine. Never abruptly withdraw; confirm the diagnosis, involve the specialist, plan the taper.

6. The Explanation — The Most Marks-Dense Minute in the Station

Use a six-step framework:

1. Legitimise and lead with the good news. 'The tests have shown you do not have MS, a stroke or epilepsy. That is genuinely good news.'

2. Name it with confidence. 'You have a condition called functional neurological disorder.'

3. Explain the mechanism with an analogy. Software, not hardware: the nervous system is structurally healthy but functioning abnormally — like a computer whose hardware is intact but whose software has glitched; like a car stuck in the wrong gear with a perfectly sound engine; like an orchestra of fine musicians who have lost coordination with each other.

4. Make it real. 'This is a real and common condition — one of the commonest I see in clinic. It is not imagined, and it is not your fault.'

5. Offer effective treatment. Specialist FND physiotherapy has the strongest evidence for motor symptoms; cognitive behavioural therapy helps dissociative attacks (demonstrated in the CODES trial); treat the common companions — pain, poor sleep, low mood, fatigue.

6. Hand back control. Signpost reputable resources such as neurosymptoms.org, arrange follow-up, agree who to contact if things worsen, and safety-net.

A script you can adapt

'I want to start by saying I believe your symptoms — they are real, and you are not imagining them. The scans and tests tell us there is no damage to the nervous system, which is genuinely good news. What we think is happening is a problem not with the structure of the nerves but with their functioning — rather like a computer with perfect hardware running faulty software. It is called functional neurological disorder. It is actually one of the commonest conditions neurologists see, it is nobody's fault, and importantly it can get better. The best treatment is a specialist physiotherapy programme that re-trains normal movement, and for some people talking therapy helps too. I would like to refer you today, give you an excellent website — neurosymptoms.org — and see you again in clinic to review progress. How does that sound?'

Say this, not that

7. Examiner Questions You Should Expect

Q: How is FND different from malingering?
A: Malingering is the intentional production or exaggeration of symptoms for external gain (money, opiates, avoiding duty). FND symptoms are involuntary and occur without that incentive. In the exam — and in life — assume FND.

Q: What investigations would you do?
A: Targeted exclusion of mimics based on the phenotype: imaging for structural disease where clinically indicated, video-EEG for attacks. Emphasise that the diagnosis is clinical and that test cascades are neither safe practice nor kind.

Q: Do antidepressants treat FND?
A: Not as a primary treatment — reserve them for comorbid depression or anxiety, which are common and worth treating in their own right.

Q: What is the prognosis?
A: Honest and variable. Shorter duration of symptoms, engagement with physiotherapy and childhood onset predict improvement; a significant minority improve substantially, some remain static, some relapse. Present it as potentially reversible with treatment, never as cured by the consultation.

Q: Can this patient drive?
A: For dissociative attacks that impair awareness, the patient must stop driving and is responsible for notifying the DVLA. The standards differ from epilepsy, so document your advice and involve the specialist. Saying nothing costs marks.

Q: Who manages FND?
A: A team: the neurologist makes and communicates the diagnosis, specialist physiotherapists deliver motor retraining, clinical psychology delivers CBT, and the general physician manages comorbid pain, mood and sleep.

8. Pitfalls That Quietly Cost Marks

• Presenting functional weakness as 'poor effort' or 'inconsistent effort' — describe the positive sign, not the person.

• Ordering every test conceivable to 'be safe' — over-investigation in FND is harmful and examiners know it.

• Forgetting the two-way rule and missing coexisting organic disease — including cord compression.

• Delivering the diagnosis apologetically or hedged — confidence is therapeutic; ambiguity breeds harm and re-presentation.

• Abruptly stopping antiepileptics in suspected NEAD without specialist confirmation.

• Failing to safety-net, signpost resources, or arrange follow-up.

9. Five Lines to Walk Into the Station With

1. Positive signs make the diagnosis: Hoover's sign, tremor entrainment, midline sensory split.

2. Dramatic weakness with normal tone, reflexes and plantars — think functional first, verify second.

3. FND and organic disease coexist — one diagnosis never switches off suspicion for the other.

4. Explain with the software–hardware analogy: real, common, treatable — never 'all in your mind'.

5. Treat with specialist physiotherapy, CBT and comorbidity control; never abruptly withdraw AEDs; remember the DVLA conversation for attacks.

The candidate who can positively diagnose FND at the bedside and kindly explain it in a consultation is demonstrating almost everything PACES exists to test: clinical method, rational investigation, safe prescribing and human decency in one station. Practise the signs until they are automatic, and rehearse the words until they are kind.