Optic nerve and chiasm abnormalities in patients with Leber hereditary optic neuropathy

This retrospective study describes the brain and orbital MRI features of patients with Leber hereditary optic neuropathy (LHON), with particular attention to the optic nerves and chiasm.

Study design

The authors examined 20 men and 8 women with an average age of 38.3 years at diagnosis, and all had genetic mutations implicated in LHON. High-resolution brain and orbital MRI studies were analyzed for each patient during the first 12 months after the onset of visual loss.

Outcomes

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 MRI, the mutation type or the sex of the patient. Nonspecific T2 white matter lesions were found in 6 patients, but without the characteristics of lesions found in patients with multiple sclerosis.

Limitations

A major limitation is the size and retrospective nature of the study. 

Clinical significance

Involvement of the posterior portions of the optic nerves may be present in patients with LHON within 1 year of onset of visual loss. Enlargement of the optic chiasm also may occur in patients with LHON. Clinically, if the patient fits the profile of LHON, an abnormal MRI of the optic nerves should not dissuade the clinician from pursuing genetic testing.