New Onset Weakness (OSCE focused)
Candidate Instructions:You are the medical student in A&E. A 72-year-old woman presents with left-sided weakness and slurred speech which started 1 hour ago.
Take a focused history to assess if this is likely to be a stroke or TIA.
Do not examine at this stage.
Key Areas to Cover ✅
- Onset and timing ⏱️ – exact time of symptom onset.
- Symptoms – weakness, speech, vision, sensation, coordination.
- Progression – improving, worsening, fluctuating?
- Past medical history – hypertension, AF, diabetes, vascular risk factors.
- Medication history – especially anticoagulants.
- Risk assessment – mobility, swallowing, safety at home.
Examiner Prompts 💬
- “What are the eligibility criteria for thrombolysis?”
- “How do you differentiate stroke from TIA?”
Differential Diagnoses 🔎
- Ischaemic stroke
- Intracerebral haemorrhage
- Hypoglycaemia
- Migraine with aura
- Seizure with post-ictal weakness (Todd’s paresis)
Mark Scheme (10 points) 📝
| Domain | Marks | Details |
|---|
| Symptom onset/timing | 2 | Establishes exact time (key for thrombolysis). |
| Neurological symptoms | 3 | Asks about weakness, speech, vision, sensation, balance. |
| Risk factors/PMH | 2 | HTN, AF, diabetes, smoking, previous stroke. |
| Drug history | 2 | Anticoagulants, antiplatelets. |
| Closing | 1 | Summarises and checks understanding. |
Teaching Commentary 📚
In OSCEs, stroke cases hinge on time of onset - this determines eligibility for thrombolysis/thrombectomy.
Always rule out mimics like hypoglycaemia. Mention risk factors (HTN, AF) and ask about anticoagulants (affects management).
A structured stroke history shows examiners you are safe and systematic.
🧑⚕️ Case Examples - New Onset Weakness
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Case 1 (Acute Ischaemic Stroke): 🧠
A 72-year-old man with atrial fibrillation develops sudden right-sided arm and leg weakness with slurred speech. CT head confirms a left MCA infarct. Diagnosis: Acute ischaemic stroke. Teaching point: Sudden focal weakness = vascular event until proven otherwise; urgent thrombolysis/thrombectomy may be indicated.
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Case 2 (Guillain–Barré Syndrome): ⚡
A 30-year-old man presents with progressive ascending weakness 1 week after diarrhoeal illness. Reflexes are absent and nerve conduction studies show demyelination. Diagnosis: Guillain–Barré syndrome. Teaching point: Look for acute, symmetrical, ascending weakness with areflexia; risk of respiratory failure → admit for monitoring and IVIG or plasma exchange.
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Case 3 (Myasthenia Gravis): 💪
A 45-year-old woman complains of fluctuating weakness, worse in the evenings, with diplopia and difficulty chewing. Tensilon test improves symptoms; acetylcholine receptor antibodies positive. Diagnosis: Myasthenia gravis. Teaching point: Fluctuating weakness + ocular/bulbar features = NMJ disorder; treat with pyridostigmine and immunosuppression.
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Case 4 (Multiple Sclerosis Relapse): 🌿
A 28-year-old woman develops subacute left leg weakness and numbness over several days. MRI brain shows demyelinating plaques. Diagnosis: Relapsing-remitting MS. Teaching point: Young adult with subacute neurological deficits → think MS; manage relapses with steroids and offer DMTs long term.
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Case 5 (Hypokalaemic Periodic Paralysis): 🧪
A 20-year-old man wakes with sudden limb weakness after a heavy carbohydrate meal and exercise the day before. Serum potassium = 2.4 mmol/L. Diagnosis: Hypokalaemic periodic paralysis. Teaching point: Electrolyte disorders can cause acute weakness; always check U&Es in unexplained weakness.
