Objective:To investigate the infarct size and its related factors in patients with anterior choroidal artery (AchA) territory infarction.Methods:From April 2016 to April 2018, consecutive patients with acute AchA territory infarction hospitalized in the Department of Neurology, the Affiliated Shuyang Hospital of Xuzhou Medical University were enrolled retrospectively. The National Institutes of Health Stroke Scale (NIHSS) was used to assess the severity of the disease at baseline, and the Diffusion-Weighted Imaging (DWI) was used to determine the side, location, size, and morphology of the infarct lesions. The patients were divided into small infarction group (<20 mm) and large infarction group (≥20 mm). Multivariate logistic regression analysis was used to determine the independent risk factors for infarct size. Results:A total of 100 consecutive patients with acute AchA territory infarction were enrolled, including 86 (86.0%) in small infarction group, 14 (14.0%) in large infarction group. Based on the NIHSS score, there were 89 patients with mild stroke, 9 with moderate stroke, and 2 with severe stroke. According to DWI, 69 patients (69.0%) had long cord-like infarcts and 31 (31.0%) had other shapes of infarcts. The baseline NIHSS score (7.0 [2.0-10.5] vs. 3.0 [2.0-4.0]; Z=2.353, P=0.019) and the proportion of patients with severe stroke (14.3% vs. 0%; P=0.018), the infarcts in posterior part of periventricular area (85.7% vs. 57.0%; χ2=4.180, P=0.041) and medial globus pallidus (21.4% vs. 4.7%; χ2=5.206, P=0.023), and cord-like infarction (92.9% vs. 65.1%; χ2=4.332, P=0.037) in patients of the large infarction group were significantly higher than those of the small infarction group; leukocyte count (7.7±1.7×10 9/L vs. 6.6±1.8×10 9/L; t=2.214, P=0.036) and platelet count (234.5±39.5×10 9/L vs. 198.0±49.4×10 9/L; t=2.618, P=0.010) were significantly higher than those of the small infarction group; the proportion of patients with sensory impairment was significantly higher than that of the small infarction group (50.0% vs. 24.4%; χ2=3.908, P=0.048). Multivariate logistic regression analysis showed that platelet count (odds ratio 1.018, 95% confidence interval 1.000-1.621; P=0.044) and stroke severity (odds ratio 18.245, 95% confidence interval 1.534-217.052; P=0.022) were significantly and positively correlated with the infarct size. Conclusion:The related factors of the infarct size in patients with AchA territory infarction included sensory impairment, baseline NIHSS score, stroke severity, morphology and location of infarct lesions, and leukocyte and platelet counts, of which platelet count and stroke severity were independently positively correlated with the infarct size.