MRI of the Optic Nerves and Chiasm in Patients With Leber Hereditary Optic Neuropathy

The aim of this study was to characterize brain and orbital MRI features of patients with Leber hereditary optic neuropathy (LHON), with particular attention to the optic nerves and chiasm. We studied a patient cohort with genetically confirmed LHON followed at 2 ophthalmologic hospitals in France between 2013 and 2015. High-resolution brain and orbital MRI studies were analyzed for each patient during the first 12 months after the onset of visual loss was analyzed. Our study included 20 men and 8 women with a mean age of 38.3 years at diagnosis, and all had genetic mutations for LHON. Nineteen patients (67.9%) had T2 hyperintensity in the posterior portion of both optic nerves and in the optic chiasm, and enlargement of the chiasm was found in 16 patients (59.3%). No enhancement of the optic nerves or chiasm was detected. The T2 hyperintensity lesions were not associated with the time between symptom onset and obtaining MRI, the mutation type, or sex of the patient. Nonspecific T2 white matter lesions were found in MRI of 6 patients, but without the characteristics of those found in patients with multiple sclerosis. Involvement of the posterior portions of the optic nerves has been described previously in case reports of patients with LHON. Our results support this observation with neuroimaging performed within 1 year of onset of visual loss. Enlargement of the optic chiasm also may occur in patients with LHON. The pathophysiology of the MRI changes is not yet understood