“Stroke mimics” are conditions that resemble stroke at first presentation, while “stroke chameleons” are strokes presenting atypically, imitating other diseases.
⏱️ Because stroke therapy is time-critical, some mimics are thrombolysed before the true diagnosis becomes clear.
🧩 Differentiating true stroke from mimics is one of the most challenging emergency skills in acute medicine.
Recognising both mimics and chameleons improves diagnostic accuracy and patient safety.

⚡ Factors Increasing the Likelihood of True Stroke

Certain features make a vascular event more likely than a mimic 👇

🚀 Sudden onset of focal neurological deficit
🕐 Clear time of onset
❤️ Atrial fibrillation or embolic risk factors
👴 Older age group
💉 Vascular risk factors: hypertension, diabetes, smoking, hyperlipidaemia
🧠 Negative neurology (loss of function rather than abnormal movement/sensation)
🩸 Deficit pattern matching a vascular territory

🚑 Common Stroke Mimics

Conditions that can look like a stroke - always worth remembering these in the acute setting.

🧩 Mimic	🩺 Clinical Clues / Teaching Points
🩸 Hypoglycaemia	Always check capillary glucose early. May mimic focal weakness or aphasia. Correct immediately before considering thrombolysis.
⚡ Seizure (Todd’s paresis)	Postictal weakness lasting up to 72 h. May be unwitnessed. CT often normal; EEG helpful if recurrent.
🦠 Sepsis / Infection	Old stroke patients may have transient deficits during infection (Old Stroke Systemic Illness). Look for fever, raised CRP/WCC, UTI or chest infection.
🧬 Encephalitis	Fever, confusion, seizures. HSV encephalitis affects temporal lobes. Confirm by MRI + CSF PCR; start IV aciclovir early if suspected.
🎗️ Brain Tumour	Gradual onset, headaches, vomiting, or seizures. MRI with gadolinium diagnostic. May bleed and appear “stroke-like”.
💧 Hyponatraemia	Severe Na < 120 mmol/L → confusion, seizures, focal deficits. Correct sodium slowly.
🌀 Positional Vertigo	Transient, position-triggered dizziness. Persistent or associated with limb ataxia suggests cerebellar stroke instead.
🧓 Subdural Haematoma	Common in elderly/anticoagulated. May mimic TIA/stroke. CT shows crescentic extra-axial collection.
🧠 Functional Disorder	Inconsistent weakness, “give-way” pattern, exaggerated drift. MRI normal. Requires sensitive communication and neurology review.
🎭 Malingering	Deliberate symptom simulation for external gain - unlike functional disorder, which is subconscious. Very rare.
🙂 Bell’s Palsy	Peripheral LMN facial palsy with forehead involvement distinguishes from central stroke (forehead sparing).
🍺 Alcohol Intoxication	Can mimic cerebellar or brainstem stroke. Always reassess when sober; do not dismiss until CT confirmed.
💥 Migraine (Hemiplegic)	Transient weakness, visual/speech disturbance. Often young with migraine history. MRI normal.
🧊 Central Pontine Myelinolysis	Following rapid sodium correction → quadriparesis, “locked-in” picture. MRI diagnostic.
🦴 Hypocalcaemia	Causes tetany, cramps, and perioral numbness. Serum calcium confirms.
🦵 Foot Drop	Peripheral (common peroneal nerve) lesion - isolated ankle dorsiflexion weakness, not hemiparesis.
🌩️ ADEM	Post-infectious demyelination. Bilateral or multifocal deficits. MRI + CSF; often treated with steroids.
🧬 Multiple Sclerosis	Relapsing pattern with optic or sensory symptoms. MRI and CSF oligoclonal bands diagnostic.
🦯 Fracture / Trauma	May mimic hemiparesis from pain/immobility. Check for history of fall or trauma and image limbs if unclear.

🎭 Stroke Chameleons - True Strokes Masquerading as Other Diseases

Strokes with atypical presentations often lead to misdiagnosis and treatment delay. Remember: not all strokes look like strokes.

🧩 Chameleon Presentation	💡 Stroke Mechanism / Explanation
🧓 Acute Delirium	Left MCA or thalamic strokes can present with confusion or dysphasia rather than weakness.
🦵 Cauda Equina Syndrome	Spinal cord infarction → paraparesis, urinary retention, saddle anaesthesia - may mimic compressive lesion.
🤲 Monoparesis	Small ACA or cortical infarcts may cause isolated limb weakness, imitating peripheral neuropathy.
💫 Syncope / Collapse	Transient LOC from posterior circulation TIA or brainstem ischaemia can mimic vasovagal syncope.
💥 Hypertensive Crisis	Very high BP in stroke is a consequence, not the cause - don’t mislabel stroke as “just hypertension.”
🥴 Acute Ataxia / “Drunk” Appearance	Cerebellar stroke → gait disturbance, dysarthria, nystagmus - easily mistaken for intoxication.
🌀 Vestibular Neuronitis	Lateral medullary or pontine stroke can mimic peripheral vertigo. Central signs: diplopia, dysarthria, or limb ataxia.

📚 References & Further Reading

Fernandes PM, Whiteley WN, Hart SR, et al. Strokes: Mimics and Chameleons. Practical Neurology 2013;13:21–28.

💡 Teaching tip: In hyperacute settings, “treat as stroke until proven otherwise” - missing a treatable infarct has greater harm than treating a mimic. However, always check glucose, temperature, infection markers, and electrolytes before thrombolysis.

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Stroke Mimics And Chameleons

🧠 Introduction

⚡ Factors Increasing the Likelihood of True Stroke

🚑 Common Stroke Mimics

🎭 Stroke Chameleons - True Strokes Masquerading as Other Diseases

📚 References & Further Reading

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