CN Palsy Incidence Associated with Glycemic Status, Duration of Diabetes

In this study, the risk of third, fourth and sixth CN palsy was higher with longer duration of diabetes. Longer diabetes duration was a major risk factor for diabetic complications such as macrovascular and microvascular events. The above graph from the study shows the cumulative incidence of third, fourth and sixth cranial nerve palsies according to glycemic status (IFG: impaired fasting glucose). Photo: Paul M. Karpecki, OD. Click image to enlarge. An acquired cranial nerve III, IV or VI palsy leading to diplopia due to extraocular muscle paresis is commonly observed in eye care. Only a few studies of cranial nerve palsy in prediabetes have been published, however. In a recent study, researchers in South Korea assessed the association between these palsies and glycemic status in people with diabetes and prediabetes; they also identified risk factors according to the glycemic status in a large cohort representative of the Korean adult population. They determined that the risk of palsy incidence significantly increased in patients with prediabetes and those who have had type 2 diabetes for five years or more.This retrospective nationwide population-based cohort study used South Korean National Health Insurance Service data from 2009 to 2018. The research team analyzed health check-up data of 4,067,842 individuals between the ages of 20 and 90. The subjects were classified according to glycemic status: nondiabetes (fasting glucose, 100mg/dL), impaired fasting glucose (fasting glucose 100mg/dL to 125 mg/dL), newly detected diabetes, diabetes duration less than five years and diabetes duration of five years or more. Impaired fasting glucose classification and diabetes were diagnosed based on American Diabetes Association guidelines. During the follow-up period (mean, 6.3 years), the researchers identified 5,835 cases of third, fourth or sixth nerve palsy.In the study, the adjusted hazard ratios for third, fourth and sixth CN palsy were 1.10 in the impaired fasting glucose group, 1.78 in the newly detected diabetes group, 1.92 in the diabetes duration less than five years group and 2.57 in the diabetes duration for five years or more group. Further analysis demonstrated an increase in the incidence of cranial nerve palsy proportional to the duration of diabetes.“In the current study, the detrimental influence of longer diabetes mellitus duration was greater in subgroups that were younger (<65 years), male, current smokers or with a history of smoking and those without hypertension,” the researchers wrote in their paper, which was published in Eye. “Longer diabetes duration is more detrimental in young patients regarding hyperglycemic complications, and therefore early aggressive treatment, with the goal of normalizing metabolic control, should be considered in this group.” The team did note that the finding that the adverse effects of diabetes duration were exacerbated in the absence of hypertension does not disqualify hypertension as a possible risk factor for palsy. Instead, it suggests that the duration of diabetes has a stronger impact on diabetic complications in patients with diabetes alone than in those with both hypertension and diabetes. Considering that the prevalence of hypertension was higher in the group with a longer duration of diabetes, it cannot be ruled out that these results were influenced by a confounding effect due to the strong correlation between hypertension and diabetes duration.Click here for the journal source. Lee C, Han KD, Yoo J, et al. The relationship between glycemic status and the risk of third, fourth and sixth cranial nerve palsy: a nationwide population-based study (2009–2018). Eye (Lond). November 7, 2025. [Epub ahead of print]. This article was developed by the editorial staff in conjunction with experts in the field. In the process, AI may have been among the editorial tools used to meet the goals of human editors, who approved all content.