Lateralization bias for autoimmune optic neuritis

•552 unilateral autoimmune optic neuritis (aON) and 374 corresponding MRIs.•Left eye aON are more frequent than right aON.•Pathological MRI findings more likely for the left than right optic nerve.•More Google searches for the left than right eye but only for aON-related symptoms.•Leftward lateralization similar to cerebral neuroinflammatory lesions. The asymmetrical structure of the human brain is reflected not only by innate interhemispheric differences but also by lateralization in neurological disease. We tested if unilateral autoimmune optic neuritis (aON) manifests more frequently on the left than the right eye in clinical and neuroimaging terms and whether Google searches for aON symptoms reflect this bias, too. We employed a retrospective analysis of a patient cohort from 2009 to 2019 with 552 unilateral aONs and 374 corresponding MRI imaging data sets. Searchmetrics Suite keywords tool was applied for the analysis of Google searches on aON-symptoms in Germany, the US and the UK for the last 12 months. Left eye aON manifestations were more frequent than right aON manifestations (55.3% vs. 44.7%, p = 0.015) and 1.9 times more likely to be associated with a pathological MRI finding in the affected optic nerve (p = 0.013). Keywords describing aON-typical but not other ocular symptoms were more frequently associated with Google searches for the left in comparison to the right eye (p < 0.001). Autoimmune optic neuritis more frequently affects the left than the right eye and people search on the Internet more often for left-sided aON symptoms. Although a reporting bias due to an increased perception of left eye symptoms is one possible explanation, MRI evidence of more frequent optic nerve affection for the left in comparison to the right side suggests a leftward lateralization bias similar to the one previously shown for cerebral neuroinflammatory lesions.