What is the next step in management for a patient presenting with facial droop and right-sided weakness with a normal head Computed Tomography (CT) scan?

Acute Management of Facial Droop and Right-Sided Weakness with Normal Head CT

Immediately obtain MRI with diffusion-weighted imaging (DWI) and vascular imaging (MRA or CTA from arch to vertex) to detect acute ischemic stroke, as CT has limited sensitivity for early infarction and posterior circulation strokes. 1, 2

Critical First Steps

Immediate Stroke Protocol Activation

• Activate stroke code immediately - facial droop with unilateral weakness represents highest-risk presentation for acute stroke, regardless of normal CT, and requires emergency evaluation within a stroke-capable facility 1, 2
• Document exact time of symptom onset (or time last known well) as this determines treatment eligibility for thrombolysis (4.5-hour window) and endovascular therapy 1
• Perform structured neurological assessment using National Institutes of Health Stroke Scale 1

Why CT Can Be Normal in Acute Stroke

• CT has poor sensitivity for hyperacute ischemic stroke - early infarction may not appear on CT for 6-24 hours, and posterior circulation strokes (pontine, thalamic) are particularly difficult to visualize on CT 3, 4
• A 90-year-old patient with bilateral thalamic stroke had initial CT that was "non-revealing," with stroke only detected on MRI several days later 3
• A 47-year-old with isolated facial palsy from pontine infarct had initial MRI "read as negative for acute stroke" until re-evaluation revealed a 4mm dorsal pontine infarct 4

Advanced Imaging Algorithm

MRI is Essential

• Obtain MRI with DWI sequences urgently - this is the gold standard for detecting acute ischemic stroke and can identify infarction within minutes of onset 1, 2
• Include MRA from arch to vertex to identify large vessel occlusion that may be amenable to endovascular therapy 1
• If MRI unavailable or contraindicated, obtain CTA to evaluate for large vessel occlusion 1

Distinguish Central vs. Peripheral Facial Palsy

• Central (stroke) pattern: facial weakness spares the forehead because of bilateral cortical innervation of upper facial muscles - patient can wrinkle forehead and close eyes 2, 5
• Peripheral (Bell's palsy) pattern: complete ipsilateral facial paralysis including forehead - patient cannot wrinkle forehead or close eye on affected side 2, 4
• Critical caveat: Pontine strokes can present with peripheral-type facial palsy mimicking Bell's palsy because the infarct affects the facial nerve nucleus itself, not cortical pathways 4

Time-Sensitive Treatment Considerations

If Stroke Confirmed on MRI

• Assess for thrombolysis eligibility if within 4.5 hours of symptom onset - intravenous alteplase (0.9 mg/kg) improves functional outcomes in acute ischemic stroke 1
• Evaluate for endovascular therapy if large vessel occlusion identified - treatment window may extend to 24 hours in selected patients 1
• Obtain electrocardiogram to assess for atrial fibrillation as stroke etiology 1

If Imaging Remains Negative

• Do not discharge immediately - observe for symptom evolution as some strokes (particularly posterior circulation) may have delayed imaging findings 3, 4
• Consider alternative diagnoses including:
  • Hemiplegic migraine (though less likely with facial droop)
  • Todd's paralysis (post-ictal weakness after unwitnessed seizure)
  • Hypoglycemia or other metabolic derangements
  • Functional neurological disorder (diagnosis of exclusion)
• Reassess anticoagulation status - if patient is anticoagulated, 24-hour observation with repeat imaging is warranted even with negative initial imaging, as delayed hemorrhage risk is 1.4-4.5% 1, 6

Critical Pitfalls to Avoid

• Never assume Bell's palsy without MRI - isolated facial palsy can be the presenting sign of pontine or frontal lobe stroke, and misdiagnosis delays critical stroke treatment 5, 4
• Never rely on CT alone - a 69-year-old initially diagnosed with peripheral facial palsy was found to have right hemisphere ischemic stroke only after detailed examination and MRI 5
• Never discharge without advanced imaging - patients presenting within 48 hours of unilateral weakness or facial droop are at highest risk for recurrent stroke (up to 10% within first week) and require immediate comprehensive evaluation 1