[Hyperintense optic nerve lesion on T2-weighted MRI imaging in the acute stage of Leber's hereditary optic neuropathy: a case report].

A 46-year-old man was admitted to our hospital for acute onset, bilateral visual disturbance. Neither papilledema nor optic atrophy was found. Brain MRI revealed a hyperintense lesion in the optic chiasm on T2-weighted imaging. No enhancement was detected in gadolinium-enhanced MRIs. Based on these results, a diagnosis of retrobulbar neuritis was made, and steroid pulse therapy was performed. However, the visual acuity did not improve at all. We therefore suspected Leber's hereditary optic neuropathy (LHON) and thus performed a PCR analysis of the mitochondrial DNA. It revealed a G to A transition at nucleotide position 11778 of the mitochondrial DNA, which has been frequently observed in LHON patients in Japan. Based on the above findings, when middle-aged patients present an acute onset of visual loss, LHON should be included in the differential diagnosis.