Neuroimaging changes in the pregeniculate visual pathway and chiasmal enlargement in Leber hereditary optic neuropathy

Purpose To describe the pattern of MRI changes in the pregeniculate visual pathway in Leber hereditary optic neuropathy (LHON). Method This retrospective observational study enrolled 60 patients with LHON between January 2015 and December 2021. The abnormal MRI features seen in the pregeniculate visual pathway were investigated, and then correlated with the causative mitochondrial DNA (mtDNA) mutation, the distribution of the MRI lesions and the duration of vision loss. Result The cohort included 48 (80%) males and 53 (88%) had bilateral vision loss. The median age of onset was 17.0 years (range 4.0–58.0). 28 (47%) patients had the m.11778G>A mutation. 34 (57%) patients had T2 hyperintensity (HS) in the pregeniculate visual pathway and 13 (22%) patients with chiasmal enlargement. 20 patients (71%) carrying the m.11778G>A mutation had T2 HS, significantly more than the 14 patients (44%) with T2 HS in the other LHON mutation groups (p=0.039). Furthermore, significantly more patients in the m.11778G>A group (16 patients (57%)) had T2 HS in optic chiasm (OCh)/optic tract (OTr) than the other LHON mutation groups (7 patients (22%), p=0.005). Optic chiasmal enlargement was more common in patients with vision loss duration <3 months compared with those ≥3 months (p=0.028). Conclusion T2 HS in the pregeniculate visual pathway is a frequent finding in LHON. Signal changes in the OCh/OTr and chiasmal enlargement, in particular within the first 3 months of visual loss, were more commonly seen in patients carrying the m.11778G>A mtDNA mutation, which may be of diagnostic significance.