Can a unilateral vertebral artery stroke cause complete blindness?

Unilateral Vertebral Artery Stroke and Complete Blindness

A unilateral vertebral artery stroke can cause complete bilateral vision loss when the stroke affects blood flow to both occipital lobes through the posterior circulation system. 1

Anatomical Basis

• The vertebral arteries merge to form the basilar artery, which branches into the posterior cerebral arteries supplying both occipital lobes
• A significant occlusion in one vertebral artery can compromise blood flow to both occipital lobes where visual processing occurs 1
• This is particularly true when:
  • The contralateral vertebral artery is hypoplastic or compromised
  • There are anatomical variations in the posterior circulation
  • The patient has inadequate collateral circulation

Clinical Presentation

Patients with complete bilateral vision loss from vertebral artery stroke typically present with:

• Sudden onset bilateral vision loss (cortical blindness)
• Preserved pupillary light reflexes (distinguishing from retinal causes) 1
• Associated vertebrobasilar symptoms:
  • Dizziness, vertigo, ataxia
  • Diplopia
  • Bilateral sensory deficits
  • Headache 2

Mechanisms of Complete Vision Loss

1. Bilateral occipital infarction: When a unilateral vertebral artery occlusion compromises flow through the basilar artery to both posterior cerebral arteries 3

2. Hemodynamic compromise: Gradual vision loss can occur due to hemodynamic stroke from vertebral artery stenosis rather than complete occlusion 2

3. Embolic phenomenon: An embolus from a diseased vertebral artery can travel to both posterior cerebral arteries 3

Diagnostic Evaluation

For patients presenting with sudden bilateral vision loss:

• Neuroimaging: MRI with diffusion-weighted imaging to detect acute ischemic changes in occipital lobes
• Vascular imaging: MRA or CTA rather than ultrasound for evaluation of vertebral arteries 1
• Catheter angiography: May be necessary when noninvasive imaging is inconclusive 1
• Visual field testing: May show bilateral inferior altitudinal defects or complete visual field loss 3

Management

Acute management:

• Consider thrombolysis if within the appropriate time window 1
• Antiplatelet therapy or anticoagulation depending on the etiology
• Blood pressure management to maintain cerebral perfusion

Secondary prevention:

• Antiplatelet therapy (aspirin plus dipyridamole has shown superior outcomes in vertebrobasilar territory) 1
• Risk factor modification (blood pressure control, lipid management, diabetes management, smoking cessation)
• Consider endovascular intervention for significant vertebral artery stenosis 2

Prognosis and Rehabilitation

• Visual recovery is variable and often incomplete
• Visual rehabilitation with prismatic spectacle correction and other optical systems can help maximize remaining vision 3
• Recent evidence suggests that visual training can recover some vision loss, even long after stroke 4
• Early intervention in the subacute period (within 6 months) shows better outcomes than training initiated later 4

Important Considerations

• Up to 44% of stroke patients with visual field defects may be unaware of their field loss 5
• Bilateral vision loss from vertebral artery stroke is distinct from monocular blindness (amaurosis fugax), which typically results from carotid artery disease 6
• Regular follow-up is essential as patients with unilateral occipital infarction have risk of developing delayed contralateral occipital infarction leading to complete cortical blindness 1

While uncommon, unilateral vertebral artery disease can indeed cause complete bilateral blindness through mechanisms affecting the posterior circulation that supplies both occipital lobes.