Patterns and Outcomes of the Top of the Basilar Artery Syndrome: The Role of the Posterior Communicating Artery.

Background: Clinical syndromes secondary to infarcts in the distal basilar artery (BA) area have been described as "top of the basilar" (TOB) syndrome. However, in the era of advanced imaging technology, it has been realized that the clinical and imaging features are quite diverse in patients with distal BA occlusion. The aim of the present study was to investigate the patterns and clinical outcomes of TOB assessed with modern images and categorize TOBs accordingly. Additionally, we examined the possible influence of the posterior communicating artery (PcoA) on the patterns of TOB.

Methods: Patients with distal BA occlusion on magnetic resonance angiography were categorized as TOB-A, and those with multiple lesions in the distal BA territory on diffusion-weighted magnetic resonance imaging as TOB-L. Patients with angiographically and lesion distribution-defined TOB were classified as having TOB-A&L; those with angiographically defined TOB as having TOB-A without TOB-L; and those with lesion distribution-defined TOB as having TOB-L without TOB-A. The PcoA was categorized as "textbook-type" (good P1) and "fetal-type" (absent P1). Factors associated with unfavorable short-term outcomes (modified Rankin Scale 5-6 at discharge), and 1-year and long-term mortalities, were assessed.

Results: Of 1,466 patients with ischemic stroke in the posterior circulation who were admitted to Asan Medical Center within 24 h of symptom onset, 124 (8.5%) had TOB, including 45 with TOB-A&L, 44 with TOB-A, and 35 with TOB-L. NIHSS scores (21 [9.5-26] vs. 6 [3-11.5] vs. 6 [3-9]; p < 0.01) and rates of motor deficit (75.6 vs. 54.5 vs. 34.4%; p < 0.01), concomitant pontine lesions (17.8 vs. 25.0 vs. 2.9%; p < 0.01), PcoA presence (44.4 vs. 68.2 vs. 25.7%; p < 0.01), and unfavorable short-term outcomes (62.2 vs. 25.0 vs. 14.3%; p < 0.01) differed significantly in the 3 patient groups. Multivariate analysis showed that textbook-type PcoA was independently associated with a lower frequency of unfavorable short-term outcomes (OR 0.15, 95% CI 0.03-0.70). Reperfusion therapy (hazard ratio [HR] 0.25, 95% CI 0.07-0.89) and the presence of textbook-type PcoA (HR 0.20, 95% CI 0.05-0.90) were associated with a lower 1-year mortality rate after stroke.

Conclusion: Patterns and clinical outcomes of TOB vary and are affected by the hemodynamic status of the arterial system, such as BA recanalization and the presence of textbook-type PcoA.