Unilateral Oculomotor Nerve Enhancement in Diabetic Oculomotor Nerve Palsy: A Retrospective Study

Background: No previous studies have explored the imaging features of oculomotor nerve palsy (ONP) in diabetic patients. In our clinical practice, isolated ONP with diabetes is partly treated with glucocorticosteroids because nerve enhancement is habitually interpreted as inflammation. Our study thus aims to summarize the imaging findings of isolated ONP with diabetes.Methods Our study included 59 patients with a clinical diagnosis of diabetic ONP. Patients were recruited from our department between January 2015 and December 2019. Orbital MRI was retrospectively analyzed for each patient, and follow-up imaging was obtained for 3 patients.Results Thickening and enhancement of the ipsilateral oculomotor nerve were detected in 38 (64.41%) patients, indicating simultaneous involvement of the cavernous segment and inferior division of the intraorbital segment. After clinically complete recovery, repeated MRI in 3 patients revealed a slightly reduced degree of enhancement of the oculomotor nerve. No differences were detected in the sex ratio (p=0.976), median onset age (p=0.563), median duration of diabetes (p=0.697), plasma glycosylated hemoglobin (HbAlc) level (p=0.278) or interval from disease onset to MRI between patients with and without enhancement of the oculomotor nerve. Conclusions Thickening and enhancement of the unilateral oculomotor nerve can be detected in patients with diabetic ONP and indicates the main involvement of the cavernous segment and the inferior division of the intraorbital segment, which may be helpful for differentiating this condition from other etiologies in isolated ONP.