Stroke risk among adult patients with third, fourth or sixth cranial nerve palsy: a Nationwide Cohort Study

Purpose This study sought to determine whether isolated third, fourth and sixth cranial nerve palsies ( NP s) are associated with increased short‐ and long‐term risk of a subsequent stroke. Methods This was a nationwide retrospective propensity score‐matched cohort study. A cohort of patients with NP ( n  = 466) and a randomly selected, propensity‐matched control cohort ( n  = 2281) were extracted from the Korean national insurance claim database. Subjects were tracked for 5 years total, subdivided into periods of 0–1 years, 1–3 years and 3–5 years. We assessed the risk of stroke using hazard ratios ( HRs ) and confidence intervals (CIs) after adjustments using Cox regression at different time intervals. Results The median follow‐up was 3.1 years. Stroke developed in 18.9% of the NP cohort and 7.5% of the control cohort. Stroke risk after NP was highest in the first year [14.7 per 100 person‐year at 0–1 years ( HR  = 6.6), 3.1 per 100 person‐year at 1–3 years ( HR  = 1.6) and 4.3 per 100 person‐year at 3–5 years ( HR  = 2.8)]. Each type of NP was also associated with stroke risk: within 0–1 years, stroke risk was increased in third ( HR  = 7.6), fourth ( HR  = 6.0) and sixth ( HR  = 5. 84) NP s. In the 3‐ to 5‐year period, risk was increased in sixth ( HR  = 4.7) and fourth ( HR  = 3.3) NP s, but not third ( HR  = 0.6) NP s. Conclusion Patients in the NP cohort were more likely to have a stroke than those in the matched control cohort; the increased risk was both time‐ and cranial nerve‐dependent.