In a patient with a prior stroke who suddenly develops a down‑and‑out eye, what is the immediate management?

Immediate Management of Down-and-Out Eye in a Patient with Prior Stroke

Treat this as an acute stroke emergency requiring immediate non-contrast CT brain imaging and urgent neurovascular assessment to determine eligibility for reperfusion therapy, as a down-and-out eye suggests a third cranial nerve palsy that could represent either a new posterior circulation stroke or a compressive lesion such as a posterior communicating artery aneurysm.

Initial Emergency Assessment

The sudden onset of a down-and-out eye (third nerve palsy) in a stroke patient demands immediate action following the same acute stroke protocol:

Immediate Steps (Within Minutes)

• Activate stroke code immediately - Time is brain, whether this represents new ischemia or another vascular emergency 1, 2
• Assess ABCs - Ensure airway, breathing, and circulation are stable, particularly if the patient has altered consciousness 3
• Determine exact time of symptom onset - This is critical for treatment eligibility. If unknown, use the time the patient was last seen normal 2
• Perform rapid neurological examination looking specifically for:
  • Pupillary involvement (dilated pupil suggests compressive lesion like aneurysm vs. pupil-sparing suggests microvascular ischemia)
  • Other brainstem signs (nystagmus, ataxia, crossed sensory findings suggesting posterior circulation stroke) 4
  • Associated eye movement abnormalities (gaze palsies, internuclear ophthalmoplegia) 5, 4

Urgent Imaging (Goal: <25 minutes from arrival) 1

Brain imaging sequence:

1. Non-contrast CT (NCCT) brain immediately - This is the priority to exclude hemorrhage and assess for acute infarction 3, 1, 6

2. CT angiography (CTA) from arch-to-vertex if presenting within 6 hours - Essential to identify:

   • Large vessel occlusion (basilar artery, posterior cerebral artery)
   • Posterior communicating artery aneurysm (critical differential for isolated third nerve palsy with pupil involvement)
   • Vertebrobasilar stenosis or occlusion 1

3. Consider MRI with diffusion-weighted imaging if CT is non-diagnostic and clinical suspicion remains high - More sensitive for posterior fossa infarctions which CT often misses 3, 6

Laboratory Tests (Do Not Delay Imaging)

Obtain simultaneously with imaging 1:

• Complete blood count
• Coagulation studies (INR, aPTT)
• Electrolytes and creatinine
• Random glucose
• Troponin and ECG

Treatment Decision Algorithm

If Presenting Within 4.5 Hours of Symptom Onset:

Consider IV thrombolysis (alteplase 0.9 mg/kg, max 90 mg) if:

• NCCT shows no hemorrhage or only early ischemic changes
• Patient meets eligibility criteria
• Blood pressure can be controlled to <185/110 mmHg 3, 2

Key consideration: Third nerve palsy alone may represent a small brainstem infarct that could benefit from thrombolysis, but if imaging suggests a large posterior circulation stroke with extensive early infarction, carefully weigh hemorrhagic transformation risk 3

If Large Vessel Occlusion Identified (Basilar or PCA):

Proceed urgently to endovascular thrombectomy if within appropriate time window (up to 24 hours for basilar occlusion in selected patients) 1, 7

If Aneurysm Identified:

Immediate neurosurgical consultation - This is a neurosurgical emergency requiring urgent intervention to prevent rupture

Critical Pitfalls to Avoid

1. Do not assume this is just a "microvascular third nerve palsy" in a diabetic or hypertensive patient without imaging - You could miss a life-threatening aneurysm or basilar stroke 8

2. Do not delay imaging to obtain ophthalmology consultation - The ophthalmologist cannot help until you exclude stroke or aneurysm 9

3. Recognize that posterior circulation strokes are easily missed - CT has poor sensitivity for brainstem infarcts; maintain high suspicion even with negative initial CT 3, 4

4. Monitor closely for neurological deterioration - Basilar artery strokes can progress rapidly with devastating consequences 5

Blood Pressure Management

• If thrombolysis candidate: Lower BP to <185/110 mmHg before treatment, maintain <180/105 mmHg for 24 hours post-treatment 1, 2
• If not receiving thrombolysis: Permissive hypertension is generally appropriate unless BP >220/120 mmHg or other compelling indication for lowering 1

Disposition

Admit to stroke unit or intensive care unit for:

• Continuous neurological monitoring
• Serial examinations for progression
• Completion of stroke workup (echocardiogram, prolonged cardiac monitoring, vessel imaging)
• Early rehabilitation assessment 3

The down-and-out eye represents a localizing sign that could indicate midbrain/fascicular third nerve involvement from posterior circulation ischemia, and the prior stroke history increases risk for recurrent events, making this a true neurological emergency requiring the full acute stroke protocol 5, 4.