MRI Demonstrates Restricted Diffusion in Distal Optic Nerve in Atypical Optic Neuritis

Abstract

A 4-year-old healthy girl with acute visual loss in the right eye had ophthalmoscopic evidence of a swollen optic disc combined with central retinal artery and vein occlusion in the affected eye. MRI showed that the intraorbital optic nerve on the affected side was thickened and enhancing. Diffusion-weighted imaging showed restricted diffusion in the distal intraorbital segment of the optic nerve, consistent with infarction attributed to compression or inflammation of the vessels serving the optic nerve and retina. Although such clinical phenomena have been described previously, this is the first patient to demonstrate restricted diffusion in an inflammatory optic neuropathy. The presence of restricted diffusion is helpful in excluding a neoplastic cause of a thickened optic nerve.

Using Diffusion-Weighted Magnetic Resonance Imaging to Confirm a Diagnosis of Posterior Ischaemic Optic Neuropathy: Two Case Reports and Literature Review

“…12,14,16 Restricted diffusion on DWI within the optic nerves has also been shown to be associated with acute inflammatory disorders such as lymphomatous optic neuropathy 17 and optic neuritis. 18 The frequency of restricted diffusion in optic neuritis is not clear; however, one retrospective study found that 8% of patients with clinical optic neuritis showed restricted diffusion on DWI. 19,20 Furthermore, changes within the optic nerve are more commonly seen with gadolinium enhanced imaging, 20 a feature not usually associated with acute ischaemic lesions.…”

Commentary

“…Restricted diffusion within the optic nerve was initially demonstrated in peri-operative PION[ 3 ] and subsequently in mucormycosis,[ 4 ] cavernous sinus thrombophlebitis,[ 5 ] thrombocytosis[ 6 ] and optic peri-neuritis. [ 7 ] Similar imaging findings in a case of lymphoma were attributed to hypercellularity due to tumor rather than infarction. [ 8 ] Infarction of the retina as well as the optic nerve has also been demonstrated in mucormycosis.…”

Hyperintense Optic Nerve Heads on Diffusion-Weighted Imaging: A Potential Imaging Sign of Papilledema

“…Several case reports have described diffusion restriction along the ON as a marker of infarction in ischemic optic neuritis, [14][15][16][17][18][19] with other studies mentioning ON diffusion restriction in the setting of infection, idiopathic orbital inflammatory syndrome, cellulitis, and orbital lymphoid lesions. 9,20,21 Although these reports describe the signal characteristics along the length of the ON, we have mainly focused on the appearance of the ON head (Figs 1 and 2).…”