MRI of the intraorbital optic nerve in patients with autosomal dominant optic atrophy

Measurements of the intraorbital optic nerve were made using high-resolutio n coronal MRI in 10 adults with autosomal dominant optic atrophy. Compariso ns were made with previous studies of 10 normal adult subjects. The cross-s ectional diameters of the optic nerve and the perineural subarachnoid space were measured and a ratio of there diameters at anterior, mid and posterio r positions along the optic nerve was determined. We found a statistically significant difference in the mean optic nerve: sheath ratio between the co ntrol group and patients with autosomal dominant optic atrophy. At anterior , mid and posterior locations along the optic nerve it is significantly sma ller in patients with optic atrophy. We have demonstrated that the loss of ganglion cells, previously documented in dominant optic atrophy, is associa ted with a significant loss of optic nerve tissue and thinning of the nerve along its length.