What emergency stroke mimics should be excluded, and how should each be evaluated using patient history, physical examination, and appropriate investigations?

Emergency Stroke Mimics: Identification and Assessment

The most critical stroke mimics to exclude emergently are hypoglycemia, seizures (Todd's paralysis), hypertensive encephalopathy, brain tumors, subdural hematoma, and toxic-metabolic disturbances, which together account for approximately 19% of patients initially diagnosed with stroke. 1, 2

Immediate Point-of-Care Assessment

Finger-Stick Glucose (First Priority)

• Obtain immediate point-of-care glucose measurement on every suspected stroke patient before any other testing, as hypoglycemia is rapidly reversible and contraindicates thrombolysis 3, 4
• Hypoglycemia (typically <50-60 mg/dL) presents with decreased level of consciousness and focal deficits that resolve with glucose administration 1, 3
• Correct hypoglycemia immediately with intravenous glucose if detected 3

Vital Signs and Initial Stabilization

• Measure blood pressure, heart rate, temperature, and oxygen saturation within the first 10 minutes 4
• Assess airway, breathing, and circulation; intubate if Glasgow Coma Scale ≤8 4

History: Key Discriminating Features

Seizure Activity (Todd's Paralysis)

• Ask specifically about witnessed seizure activity or history of epilepsy 1
• Look for postictal period following the deficit 1
• Todd's paralysis presents as unilateral weakness after a seizure and typically resolves within 24-48 hours 1

Metabolic and Toxic Causes

• History of diabetes increases likelihood of hypoglycemia as the mimic 1
• History of alcohol abuse suggests Wernicke's encephalopathy (triad: ataxia, ophthalmoplegia, confusion) 1, 3
• Current medications: Lithium, phenytoin, or carbamazepine toxicity can mimic stroke 1
• Recent drug abuse or presence of endocarditis/medical device implants suggests CNS abscess 1

Hypertensive Encephalopathy

• Headache, delirium, and significantly elevated blood pressure (typically >220/120 mmHg) with cortical blindness or seizures 1, 3
• May show cerebral edema on imaging 1

Migraine with Aura

• History of similar preceding events with aura followed by headache 1
• Symptoms typically develop more gradually than stroke 1

Tumor or Subdural Hematoma

• Gradual progression of symptoms rather than abrupt onset 1
• History of other primary malignancy 1
• Seizure at onset may suggest tumor 1
• History of trauma (even remote) suggests subdural hematoma 1

Physical Examination: Distinguishing Features

Findings That Increase Likelihood of Mimic

• Decreased level of consciousness significantly increases odds of mimic (multivariate analysis shows this is the strongest predictor) 2
• Normal eye movements increase likelihood of mimic 2
• Lack of objective cranial nerve findings or neurological findings in a non-vascular distribution suggest psychogenic cause 1
• Inconsistent examination findings point to psychogenic etiology 1

Findings That Decrease Likelihood of Mimic (Favor True Stroke)

• Abnormal visual fields decrease odds of mimic 2
• Diastolic blood pressure >90 mmHg decreases odds of mimic 2
• Atrial fibrillation on ECG strongly favors true stroke 2
• History of angina decreases odds of mimic (strongest negative predictor in multivariate analysis) 2

Standardized Neurological Assessment

• Perform NIH Stroke Scale (NIHSS) immediately to quantify deficits and guide treatment decisions 5, 4
• Assess level of consciousness, focal deficits, cranial nerves, motor function, reflexes, and Babinski signs 5

Investigations: Systematic Approach

Emergent Brain Imaging (Within 25 Minutes)

• Non-contrast CT brain is mandatory first-line imaging to exclude hemorrhage, tumor, subdural hematoma, and other structural lesions 1, 4, 6
• CT must be completed within ≤25 minutes of arrival for thrombolysis candidates 4
• Do not delay imaging while waiting for laboratory results 4

Laboratory Tests (Obtain Simultaneously, Do Not Delay Imaging)

• Complete blood count (to detect infection, thrombocytopenia) 1, 4
• Serum glucose (if not already obtained via finger-stick) 1, 4
• Serum electrolytes and renal function (to identify metabolic disturbances) 1, 4
• Coagulation profile (PT/INR, aPTT) if patient on anticoagulants 1, 4
• Serum osmolality if metabolic encephalopathy suspected 3
• Toxicology screen only if drug toxicity suspected based on history 1, 3
• Blood alcohol level if clinically indicated 1

Additional Investigations for Specific Mimics

• Lumbar puncture only if subarachnoid hemorrhage suspected and CT negative for blood 1
• EEG if seizures are suspected based on history or examination 1
• Chest radiography only if lung disease suspected 1
• 12-lead ECG to identify atrial fibrillation or acute myocardial infarction 5, 4

Advanced Imaging When Initial CT is Negative

• MRI with diffusion-weighted imaging (DWI) is more sensitive than CT for small infarcts and posterior circulation strokes 5, 6
• Consider MRI if initial CT is negative but clinical suspicion remains high 3, 6

Critical Pitfalls to Avoid

• Never delay thrombolytic therapy waiting for laboratory results unless there is clinical suspicion of bleeding abnormality, thrombocytopenia, or known anticoagulant use 1, 5
• Do not dismiss "mild" or rapidly improving symptoms—large vessel occlusions can present with fluctuating deficits 4
• Sensitivity of clinical prediction models for mimics is only 21%, so maintain high index of suspicion and proceed with imaging 2
• Global neurological symptoms (confusion, decreased consciousness) are more common in mimics than focal deficits, but this distinction is not reliable enough to exclude stroke 1, 2
• Do not administer thrombolytics to patients with hypoglycemia until glucose is corrected and symptoms reassessed 3, 4