What is the most likely diagnosis for a patient presenting with headache and right-sided numbness?

Acute Stroke Until Proven Otherwise

A patient presenting with headache and right-sided numbness requires immediate evaluation for acute stroke, particularly cerebral venous thrombosis (CVT) or arterial ischemic stroke, as these represent life-threatening emergencies where timely intervention directly impacts mortality and long-term disability.

Critical Differential Diagnosis

The combination of headache with unilateral numbness is a red flag for secondary headache requiring urgent neuroimaging 1. The most critical diagnoses to exclude immediately are:

Primary Considerations (Life-Threatening):

1. Ischemic Stroke (Arterial)

• Right-sided numbness suggests left hemisphere involvement
• Headache occurs in approximately 25-30% of ischemic strokes
• Time-critical: thrombolysis window is 4.5 hours from symptom onset
• Look for: sudden onset, associated weakness, speech changes, facial droop

2. Cerebral Venous Thrombosis (CVT)

• Headache is present in nearly 90% of CVT cases 2
• Focal neurological signs (including sensory symptoms like numbness) occur when venous ischemia/infarction develops
• The headache typically progresses over days to weeks, but can present acutely
• Critical point: CVT can present with isolated headache in 25% of cases, making focal signs like numbness highly significant 2
• Bilateral involvement is possible but unilateral presentations are common
• Seizures occur in 40% of CVT patients 2

3. Intracranial Hemorrhage

• Subarachnoid hemorrhage can present with thunderclap headache
• Intracerebral hemorrhage may cause focal deficits with headache

Secondary Considerations:

4. Vertebral Artery Dissection

• Can present with neck pain, headache, and focal neurological deficits 3
• More common in younger patients
• May mimic cerebral stroke despite being a posterior circulation issue

5. Space-Occupying Lesion

• Progressive headache with focal signs suggests tumor, abscess, or other mass 1
• Atrial myxoma can cause cardiogenic emboli presenting with headache and numbness 4

Immediate Diagnostic Approach

Do not waste time with a "comprehensive history"—focus on these specific elements:

Time-Critical Questions (< 2 minutes):

• Exact time of symptom onset (determines thrombolysis eligibility)
• Sudden vs. gradual onset (sudden = arterial stroke; gradual = CVT or mass)
• Associated symptoms: weakness, speech changes, vision changes, seizures
• Recent head trauma, neck manipulation, or infection
• Hypercoagulable risk factors: oral contraceptives, pregnancy, cancer, thrombophilia

Focused Neurological Examination:

• Facial symmetry and strength
• Arm/leg motor strength bilaterally
• Sensory testing in all extremities
• Speech assessment (fluency, comprehension, repetition)
• Visual fields
• Gait if safe
• Signs of increased intracranial pressure: papilledema, sixth nerve palsy

Mandatory Immediate Testing:

1. Non-contrast CT head (within 20 minutes of arrival)

   • Rules out hemorrhage before considering thrombolysis
   • May show hyperdense vessel sign in acute stroke
   • Often normal in early ischemic stroke and CVT

2. CT or MR Angiography with venography

   • Essential for diagnosing CVT 2
   • Identifies arterial occlusions
   • MRI with diffusion-weighted imaging is more sensitive for acute ischemia

3. ECG and cardiac monitoring

   • Atrial fibrillation is a major stroke risk factor

4. Basic labs: glucose, electrolytes, CBC, coagulation studies

Management Algorithm

If Arterial Ischemic Stroke Confirmed:

• Thrombolysis (alteplase or tenecteplase) if within 4.5 hours and no contraindications
• Mechanical thrombectomy consideration for large vessel occlusion (up to 24 hours in selected cases)
• Antiplatelet therapy if thrombolysis not given

If CVT Confirmed:

• Anticoagulation with therapeutic heparin is standard treatment 2
• Continue despite presence of hemorrhagic infarction in most cases
• Treat seizures if present
• Monitor for increased intracranial pressure

If Vertebral Artery Dissection:

• Antiplatelet or anticoagulation therapy
• Consider thrombolysis in selected cases 3

Critical Pitfalls to Avoid

1. Do not dismiss headache as "just migraine" in the presence of focal neurological signs—this is an atypical aura red flag 1

2. Do not delay imaging because the patient is "too young" for stroke—CVT and dissections preferentially affect younger patients

3. Do not assume normal initial CT excludes stroke—early ischemic changes are subtle, and CVT is frequently missed on non-contrast CT

4. Do not withhold anticoagulation in CVT due to fear of hemorrhage—hemorrhagic transformation is common in CVT, but anticoagulation remains the standard treatment 2

5. Consider neurosyphilis in patients with cranial nerve involvement and systemic symptoms, though this is less acute 5

Bottom Line

Headache with unilateral numbness is stroke until proven otherwise. Immediate neuroimaging with both arterial and venous studies is mandatory. The specific pattern of symptom onset (sudden vs. progressive) and associated features guide the differential, but time to imaging and potential intervention is the primary determinant of outcome—every minute of delay increases disability and mortality risk in acute stroke.