Plaque distribution of low-grade basilar artery atherosclerosis and its clinical relevance

BACKGROUND The underlying pathophysiology of BA distribution is unclear and intriguing. Using high-resolution magnetic resonance imaging (HR-MRI), we sought to explore the plaque distribution of low-grade basilar artery (BA) atherosclerosis and its clinical relevance. METHODS We retrospectively analyzed the imaging and clinical data of 61 patients with low-grade atherosclerotic BA stenosis (<50%). On HR-MRI, the plaques were categorized based on the involvement of the ventral, dorsal, or lateral sides of BA wall. A culprit plaque was defined if it was on the same slice or neighboring slices of symptomatic pontine infarcts and played a probable causal role (dorsal plaques with median pontine infarcts or lateral plaques with ipsilateral pontine infarcts). The relationships between plaque distribution and clinical presentations were analyzed. RESULTS Twenty-five symptomatic and thirty-six asymptomatic BAs with 752 HR-MRI image slices were studied. The average length of BA atherosclerosis plaques was 12.16 ± 5.61mm (10.30 ± 6.44mm in symptomatic and 13.46 ± 7.03mm in asymptomatic patients, p = 0.079). The plaque distribution was similar at ventral (29.0%), dorsal (37.6%) and lateral walls (33.1%). The BA plaques in symptomatic patients were more frequently located at the dorsal (42.5%) and lateral (41.2%) walls than at the ventral walls (16.1%; P < 0.05). Compared with symptomatic patients, asymptomatic patients more likely had their plaques distributed at the ventral walls (P = 0.022). Culprit plaques were observed in 85.0% (17/20) pontine infarcts in symptomatic patients and only 14.3% (2/14) silent pontine infarcts in asymptomatic patients (p < 0.001). CONCLUSIONS Low-grade BA atherosclerosis has a long distribution and evenly involves ventral, dorsal and lateral walls. The plaques at dorsal and lateral walls are associated with symptomatic pontine infarcts but not with silent infarcts.