How to evaluate for vertebral artery occlusion?

Evaluation for Vertebral Artery Occlusion

In patients with suspected vertebral artery occlusion, MRA or CTA is the recommended first-line imaging modality rather than ultrasound due to superior sensitivity and specificity for detecting vertebral artery disease. 1

Clinical Presentation

Symptoms associated with vertebral artery occlusive disease include:

• Dizziness, vertigo, diplopia, perioral numbness, blurred vision, tinnitus, ataxia, bilateral sensory deficits, and syncope 1
• Occipito-cervical headache often precedes other symptoms 2
• Symptoms may be provoked by head turning, especially when lesions occur at the midportion of the vertebral arteries 1
• Multiple ischemic episodes may occur, with higher risk of early recurrent stroke 1

Diagnostic Algorithm

Step 1: Initial Assessment

• Identify patients at high risk who should undergo screening:
  • Patients with asymptomatic bilateral carotid occlusions 1
  • Patients with unilateral carotid artery occlusion and incomplete circle of Willis 1
  • Patients with symptoms suggesting posterior cerebral or cerebellar ischemia 1

Step 2: Noninvasive Imaging

• First-line imaging: MRA or CTA (sensitivity 94%, specificity 95%) 1
  • These are superior to ultrasound imaging (sensitivity only 70%) for evaluation of vertebral arteries 1
  • Both techniques can effectively detect stenosis and occlusion 1

Step 3: Advanced Imaging (when indicated)

• Catheter-based contrast angiography:
  • Indicated when noninvasive imaging fails to define location or severity of stenosis 1
  • Particularly useful in patients who may be candidates for revascularization 1
  • Required before revascularization for patients with symptomatic posterior cerebral ischemia as neither MRA nor CTA reliably delineate the origins of the vertebral arteries 1

Step 4: Dynamic Studies (for suspected rotational occlusion)

• Dynamic angiography with progressive head rotation:
  • Gold standard for diagnosing rotational vertebral artery occlusion 3, 4
  • Less invasive alternatives include dynamic Angio-CT, Angio-MRI, or Doppler ultrasonography 4
  • Critical for identifying occlusion sites that may only be apparent during head movement 3

Special Considerations

Anatomical Variants

• The vertebral arteries have 4 segments (V1-V4), with the first 3 being extracranial 1
• Approximately 5% of individuals have the left vertebral artery arising from the aortic arch rather than the subclavian artery 1
• Common sites of occlusion:
  • Proximal (V1) segment - most common site of atherosclerotic stenosis 1
  • C1-C2 level (V3) - common site for rotational occlusion 3, 4
  • Distal segments (V3, V4) - can lead to more severe neurological deficits 2

Follow-up Imaging

• For patients with symptoms of posterior cerebral or cerebellar ischemia, serial noninvasive imaging is reasonable to:
  • Assess progression of atherosclerotic disease 1
  • Exclude development of new lesions 1
• After vertebral artery revascularization, follow-up imaging should occur at intervals similar to those for carotid revascularization 1

Pitfalls to Avoid

• Failing to consider rotational vertebral artery occlusion when symptoms are provoked by head turning 3, 4
• Relying solely on static imaging when dynamic occlusion is suspected 3
• Misdiagnosing the site of occlusion or missing a second occlusive site 3
• Assuming unilateral vertebral artery occlusion is always benign - mortality can reach 25% in some cases 2
• Neglecting to perform contralateral vertebral arteriogram when assessing vertebral artery injury 5

By following this systematic approach to evaluation, clinicians can effectively diagnose vertebral artery occlusion and determine appropriate management strategies to reduce the risk of posterior circulation stroke and associated morbidity and mortality.