Hypoplastic Vertebral Artery: Frequency and Associations with Ischaemic Stroke Territory

Background: In patients with posterior inferior cerebellar artery infarction (PICAI) or lateral medullary infarction (LMI), the ipsilateral vertebral artery is often hypoplastic and therefore at an increased risk of ischaemic stroke.

Objective: To investigate the frequency and clinical relevance of hypoplastic vertebral artery (HVA) in patients with ischaemic stroke with or without vertebral artery territory and in normal healthy people.

Methods: 529 patients with ischaemic stroke, including vertebral artery territory infarction (LMI or PICAI), were classified according to their stroke location (303 anterior circulation strokes (ACS) and 226 posterior circulation strokes (PCS)) by MRI. The frequency of HVA, defined as a diameter of < or = 2 mm by magnetic resonance angiography, was measured in comparison with 306 normal healthy people.

Results: 185 patients (35.2%) from the cohort had HVA (3.4%, bilaterally). Patients with PCS showed a higher rate of HVA than those with ACS (45.6% vs 27.1%, p<0.001). The HVA frequency of those with ACS was similar to that of the normal group (26.5%). Of the 112 patients with vertebral artery territory stroke, 58 (51.8%) had HVA (bilateral HVA in 10), and all of 48 showed ipsilateral HVA territory stroke. In 102 patients with vertebral artery territory stroke, classification of the ipsilateral vertebral artery as hypoplastic (vs dominant or symmetric) tended to predict the involvement of multiple and extensive lesions, and a higher incidence of steno-occlusion (p<0.001).

Conclusion: HVA is not rare in the normal population, and is frequent in patients with PCS. People with HVA may have a high probability of PCS, with atherosclerotic susceptibility and ipsilateral lesions in the vertebral artery territory.