What other diagnoses should be considered in a patient with left‑sided weakness and facial droop besides a cerebrovascular accident?

Differential Diagnosis of Left-Sided Weakness and Facial Droop

The most critical immediate priority is to distinguish between central (stroke) and peripheral (Bell's palsy) facial nerve involvement, as this determines whether the patient requires emergent stroke protocols or outpatient corticosteroid therapy. 1, 2, 3

Key Distinguishing Features

Central vs. Peripheral Facial Weakness

The ability to wrinkle the forehead is the single most important clinical finding:

• Peripheral facial palsy (Bell's palsy): Complete facial weakness including inability to close the eye or wrinkle the forehead on the affected side, with NO other neurological deficits 3, 4
• Central stroke: Forehead sparing (patient CAN wrinkle forehead) because of bilateral cortical innervation of the upper face, typically accompanied by limb weakness or other neurological signs 1, 2, 5

Critical Pitfall to Avoid

Frontal lobe ischemic stroke can rarely present with isolated peripheral-type facial palsy without obvious limb weakness initially, making this a crucial diagnostic trap. 4 The American Heart Association emphasizes that detailed neurological examination beyond just facial assessment is mandatory to avoid missing stroke. 1

Differential Diagnoses Beyond CVA

1. Bell's Palsy (Idiopathic Peripheral Facial Nerve Palsy)

• Acute onset unilateral facial weakness with complete involvement of upper and lower face 3
• No limb weakness, no speech disturbance, no sensory deficits 3
• Diagnosis of exclusion requiring absence of other neurological findings 3
• Treatment: Prednisone 60-80 mg daily within 72 hours of onset 3

2. Hemiplegic Migraine

• Can mimic stroke with unilateral weakness and facial symptoms 1
• History of similar episodes with complete resolution is key 1
• Younger patients without vascular risk factors 1
• Requires neuroimaging to exclude stroke before diagnosis 1

3. Todd's Paralysis (Post-Ictal Paralysis)

• Transient weakness following seizure activity 1
• History of witnessed seizure or tongue biting, incontinence 1
• Typically resolves within 24-48 hours 1
• Requires EEG and neuroimaging to exclude structural lesion 1

4. Hypoglycemia

• Can present with focal neurological deficits mimicking stroke 1
• Immediate fingerstick glucose is mandatory in all patients with acute weakness 1
• Rapid reversal with glucose administration confirms diagnosis 1

5. Thrombotic Thrombocytopenic Purpura (TTP)

• Can present identically to ischemic stroke with sudden weakness and facial droop 6
• Early stages may not show thrombocytopenia or schistocytes initially 6
• Complete blood count with peripheral smear is essential 6
• Requires urgent plasma exchange if diagnosed 6

6. Cardiac Embolism from Atrial Myxoma

• Young patients (<35 years) with stroke symptoms should prompt evaluation for embolic sources 7
• Point-of-care ultrasound can identify left atrial masses 7
• Mobile left atrial mass on echocardiography confirms diagnosis 7

7. Intracranial Hemorrhage

• Can present with identical symptoms to ischemic stroke 1, 2
• Non-contrast CT head is mandatory to exclude before any thrombolytic therapy 2, 5
• Anticoagulation or antiplatelet use increases risk 1

8. Posterior Circulation Stroke (Vertebrobasilar)

• Bilateral intracranial vertebral artery occlusions can cause progressive cranial neuropathies including facial droop 8
• Associated with ataxia, cranial nerve deficits, dizziness 1
• May present with ipsilateral facial weakness and contralateral body weakness (crossed findings) 1, 5

9. Cerebral Vasospasm

• Can occur even after uneventful neurosurgical procedures 9
• Sudden onset weakness and facial droop days to weeks after intracranial surgery 9
• Requires angiography for diagnosis and nimodipine treatment 9

10. Functional Neurological Disorder (Conversion Disorder)

• Diagnosis of exclusion only after comprehensive workup 1
• Inconsistent examination findings, non-anatomic patterns 1
• Should never be assumed without neuroimaging to exclude organic pathology 1

Mandatory Immediate Workup

Every patient with acute unilateral weakness and facial droop requires:

• Time last known normal - single most critical piece of information for treatment eligibility 2, 5
• Fingerstick glucose immediately - hypoglycemia must be excluded first 1
• Non-contrast CT head - to exclude hemorrhage and identify early ischemic changes 2, 5
• Complete neurological examination including:
  • Forehead wrinkling ability (central vs peripheral) 3, 4
  • Limb strength testing bilaterally 1
  • Speech assessment for aphasia 1, 5
  • Visual field testing 1
  • Cranial nerve examination 1
• National Institutes of Health Stroke Scale (NIHSS) - quantifies stroke severity 1, 2
• Complete blood count with peripheral smear - to exclude TTP 6
• ECG - to identify atrial fibrillation or other arrhythmias 1

Treatment Algorithm Based on Findings

If forehead IS spared (can wrinkle) OR any limb weakness present:

• Activate stroke alert immediately 2, 5
• Transfer to stroke center with tPA capability 1, 2
• CT angiography from aortic arch to vertex for large vessel occlusion 2, 5
• Consider IV tPA if within 3-4.5 hours and no contraindications 2, 5

If complete facial involvement (cannot wrinkle forehead) AND no other deficits:

• Consider Bell's palsy but obtain MRI brain to exclude stroke 3, 4
• Initiate prednisone 60-80 mg daily if Bell's palsy confirmed 3
• Aggressive corneal protection immediately 3

The stakes are too high to miss stroke - when in doubt, treat as stroke until proven otherwise. 1, 2, 5