Magnetic resonance imaging, magnetisation transfer imaging, and diffusion weighted imaging correlates of optic nerve, brain, and cervical cord damagein Leber's hereditary optic neuropathy

Objectives-Leber's hereditary optic neuropathy (LHON) is a mitochondrial di sease leading to bilateral loss of central vision and severe optic nerve at rophy. A subtype of LHON presents additional clinical and MRI aspects indis tinguishable from those of multiple sclerosis (MS) (LHON-MS). In patients w ith LHON or LHON-MS, an assessment was made of (a) the severity of optic ne rve damage, using MRI and magnetisation transfer imaging (MTI), and (b) the presence and extent of macroscopic and microscopic pathology in the brain and cervical cord, using MRI and MT ratio (MTR) and mean diffusivity ((D) o ver bar) histogram analysis. Methods-Ten patients with LHON, four with LHON-MS, and 20 age and sex match ed healthy controls were studied. For the optic nerve and the brain, dual-e cho turbo spin echo (TSE), T1 weighted spin echo, and MT images were obtain ed. For the brain, fast fluid attenuated inversion recovery (fast FLAIR) an d diffusion weighted images were also obtained. For the cervical cord, fast short tau inversion recovery (STIR) and MT images were obtained. The volum e and the average MTR value of both the optic nerves were measured. MTR and (D) over bar histograms of the normal appearing brain tissue (NABT) and MT R histograms of the whole cervical cord tissue were created. Results-The mean values of optic nerve volumes and MTR were significantly l ower in patients with LHON than in healthy controls. Mean NABT-MTR histogra m peak height was significantly lower in patients with LHON than in control s, whereas no significant difference was found for any of the cervical cord MTR histogram derived measures. Average diffusivity ((D) over bar) was hig her in patients with LHON than in controls. Optic nerve volume and MTR valu e and mean NABT-MTR were lower in patients with LHON-MS than in those with LHON. Conclusions-The severity of optic nerve pathology in LHON is measurable in vivo using MRI and MTI. MTR and (D) over bar histogram analysis suggests th at microscopic brain damage occurs in LHON and that it is more severe in th e MS-like form of the disease.