What is the most likely diagnosis and acute emergency management for a patient presenting with acute right‑hand weakness and right‑sided numbness?

Acute Left Middle Cerebral Artery Stroke

A patient presenting with acute right-sided weakness and numbness most likely has an acute ischemic stroke in the left middle cerebral artery (MCA) territory and requires immediate transfer to an emergency department or stroke center for non-contrast CT head, establishment of symptom onset time, and consideration for IV thrombolysis (within 4.5 hours) or endovascular thrombectomy (up to 24 hours). 1, 2

Anatomical Localization

The clinical presentation localizes to the left cerebral hemisphere, specifically the left MCA territory:

• Right-sided motor weakness indicates damage to the left motor cortex or descending corticospinal tract, as motor pathways decussate in the brainstem 3, 1
• Right-sided sensory loss (numbness) reflects involvement of the left sensory cortex or thalamus 3
• The combination of face, arm, and potentially leg involvement is classic for MCA territory stroke 2
• This is not a brainstem stroke—brainstem lesions produce crossed findings (ipsilateral facial weakness with contralateral body weakness), which are absent here 1, 2

Most Likely Diagnosis

Acute ischemic stroke in the left MCA distribution is the primary diagnosis based on:

• The left MCA is the most frequent vascular source for right-sided hemiparesis and hemisensory loss 1
• Left internal carotid artery occlusion can produce identical findings since the MCA is its principal branch 3
• The patient may also have aphasia (language disturbance), which would further confirm left-hemisphere involvement in a right-handed individual 3

Acute Emergency Management Protocol

Immediate Actions (First 10 Minutes)

Establish the exact time of symptom onset or "last known well" time:

• This single determination dictates all treatment eligibility 2, 4
• If the patient woke with symptoms, the "last known well" time is when they went to sleep 4
• IV tPA eligibility requires onset within 4.5 hours; endovascular thrombectomy may be performed up to 24 hours in select patients 2, 4

Activate emergency medical services (EMS) and transfer immediately to a stroke center:

• The patient requires a facility with on-site brain and vascular imaging, IV tPA capability, and access to endovascular thrombectomy 3, 2
• EMS should provide prehospital notification to activate the stroke team before arrival 3
• Supplemental oxygen should be administered only if oxygen saturation is <94% 3

Perform rapid stroke assessment using the Cincinnati Prehospital Stroke Scale:

• Check for facial droop, arm drift, and abnormal speech—a single abnormality has 72% probability of stroke 3, 4
• Complete the full National Institutes of Health Stroke Scale (NIHSS) to quantify stroke severity 4

Emergency Department Management (First 60 Minutes)

Obtain non-contrast CT head immediately:

• This is the minimum required imaging to exclude intracranial hemorrhage before thrombolysis 2, 4
• Early ischemic changes may include hypodensity in the left MCA territory, loss of gray-white differentiation, or effacement of the left lentiform nucleus 1

Complete CT angiography (CTA) from aortic arch to vertex:

• CTA identifies large-vessel occlusion (left ICA or MCA) amenable to endovascular thrombectomy 3, 1, 2, 4
• This can be performed at the time of initial brain CT and should not delay thrombolysis if the patient is within the time window 3, 4

Obtain laboratory tests within 60 minutes:

• Complete blood count with platelets, serum electrolytes, creatinine, glucose, coagulation studies (aPTT, INR), and troponin 3, 4
• Check blood glucose immediately—hypoglycemia can mimic stroke 3

Assess vital signs and manage blood pressure appropriately:

• Do NOT treat hypertension aggressively—cerebral perfusion depends on elevated blood pressure in acute stroke 2, 4
• Blood pressure should only be lowered if >185/110 mmHg for tPA candidates or >220/120 mmHg otherwise 4
• Avoid glucose-containing IV fluids unless the patient is hypoglycemic 3

Thrombolytic Therapy Decision

Administer IV tPA if eligible (within 4.5 hours of symptom onset):

• Follow published guidelines for emergency stroke care and thrombolytic therapy 3
• The American Heart Association/American Stroke Association guidelines provide specific inclusion and exclusion criteria 3

Consider endovascular thrombectomy if large-vessel occlusion is identified:

• Mechanical thrombectomy is recommended for proximal artery occlusions in the anterior circulation within 24 hours of symptom onset 3
• This is performed in addition to IV tPA, or as first-line treatment if tPA is contraindicated 3

Critical Pitfalls to Avoid

• Do not delay care to obtain extensive vascular imaging—non-contrast CT is sufficient to initiate thrombolysis 4
• Do not treat hypertension aggressively unless BP exceeds the thresholds noted above 2, 4
• Do not miss the time window—every minute counts, and delayed recognition results in poor outcomes 4
• Do not assume isolated symptoms are benign—even isolated dysarthria or sensory symptoms can represent acute stroke 4
• Do not fail to recognize atypical presentations—right-sided strokes may present later to the emergency department because symptoms are less easily recognized 5, 6

Additional Considerations

Document vascular risk factors:

• Hypertension (most important modifiable risk factor), diabetes, atrial fibrillation, prior stroke/TIA, smoking, hyperlipidemia, coronary artery disease 2, 4

Monitor for complications:

• Large left MCA infarcts involving >50% of the MCA territory can precipitate malignant cerebral edema within 24-96 hours 1
• Continuous monitoring for deteriorating consciousness, pupillary changes, or worsening neurological status is essential 1
• Early decompressive hemicraniectomy may be required for extensive infarctions in patients <60 years old 1

Recognize that left-hemisphere strokes have better outcomes after thrombolysis:

• Despite higher baseline NIHSS scores, patients with left-hemisphere strokes have a 2-fold increased chance of good outcome at 3 months compared to right-hemisphere strokes 5
• Female sex and left-hemisphere location are independent predictors of major neurological improvement at 24 hours after IV tPA 5