Vascular Risk Factors in Isolated Microvascular Ischemic Third Nerve Palsy: A Population-Based Study

Background:Although presumed microvascular third nerve palsies (TNP) have been associated with vascular risk factors and/or stroke, these associations have not been explored in a population-based cohort. The purpose of this population-based case-control study was to determine whether these factors are associated with TNPs that had been classified as isolated microvascular ischemic events and determine future risk of mortality.Methods:Participants were subjects >18 years old with new onset of isolated TNP attributed to presumed microvascular ischemia (n = 55) while residing in Olmsted County, Minnesota, from January 1, 1978 to December 31, 2014. Control subjects (n = 55) were randomly selected from the same population and matched for gender, age, and length of medical follow-up. We identified all cases of new-onset isolated presumed microvascular ischemic TNP using the Rochester Epidemiology Project, a record-linkage system of medical records for all patient-physician encounters in Olmsted County, Minnesota. All medical records of cases and controls were reviewed for potential risk factors, including diabetes mellitus, diabetic retinopathy, hypertension, hyperlipidemia, smoking, and symptomatic ischemic stroke. Multivariable and univariate logistic regression analyses were used to compare the prevalence of potential risk factors between microvascular ischemic cases and controls according to the number of subjects, and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Kaplan-Meier curves were used to compare mortality between cases and controls.Results:The annual incidence of microvascular ischemic TNP was 1.7 per 100,000. Univariate analysis demonstrated that hypertension (P < 0.001; OR, 4.80; 95% CI, 2.11-11.58), diabetes mellitus (P < 0.001; OR, 6.55; 95% CI, 2.72-17.32), diabetic retinopathy (P = 0.014; OR, 13.50; 95% CI, 2.48-251.55), coronary artery disease (P = 0.047; OR, 2.27; 95% CI, 1.02-5.18), and symptomatic ischemic stroke (P = 0.039; OR, 3.56; 95% CI, 1.07-11.85) all occurred more frequently in patients with microvascular ischemic TNP than controls. In multivariate analysis, only hypertension (OR of 4.14, 95% CI, 1.61-10.65, P < 0.001) and diabetes (OR of 4.12, 95% CI, 1.43-11.92, P = 0.003) remained independently statistically significant. There was numerically higher mortality in microvascular cases than in controls, but it did not reach statistical significance.Conclusions:There are multiple cardiovascular diseases that are associated with isolated microvascular ischemic TNP, including hypertension, coronary artery disease, diabetes mellitus, diabetic retinopathy, and symptomatic ischemic stroke. Given that the main drivers of this association seem to be diabetes and hypertension, patients with microvascular ischemic TNP should be evaluated for these conditions.