['To assess the association of Hemoglobin A1C (HbA1c) with acute brainstem infarctions (BSIs) and to determine whether HbA1c is an independent risk factor in BSIs patients.', '96 only BSIs patients were categorized into four groups according to HbA1c as <6%, ≥ 6% but <7%, ≥ 7% but <8%, or ≥ 8%, respectively. The association of the four HbA1c groups with diffusion-weighted imaging (DWI) infarct volumes (DIV), National Institutes of Health Stroke Scale (NIHSS), and follow-up modified Rankin Scale (FmRS) scores were analyzed. Patients also were categorized into two groups according to HbA1c<6% or ≥ 6%. Logistic regression analyses were performed to determine independent risk factors.', 'There was a significant correlation between HbA1c and DIV (Spearman ρ=0.339, P=0.001), NIHSS scores (ρ=0.292, P=0.004) and FmRS scores (ρ=0.315, P=0.002). The incidence of pons infarction was highest in BSIs and patients with HbA1c ≥ 6% showed significantly more frequent isolated pontine infarction. Logistic regression analyses showed that only HbA1c was independently associated with larger DIV (P=0.025) and FmRS scores (P=0.026).'] Is hemoglobin A1C independently associated with severity and prognosis of brainstem infarctions?