Optical coherence tomography differs in neuromyelitis optica compared with multiple sclerosis

Abstract

Background: Neuromyelitis optica (NMO) is associated with destructive inflammatory lesions, resulting in necrosis and axonal injury. Disability from multiple sclerosis (MS) is due to a combination of demyelination and varying axonal involvement. Optical coherence tomography (OCT), by measuring retinal nerve fiber layer (RNFL) as a surrogate of axonal injury, has potential to discriminate between these two conditions.

Methods: Included were 22 subjects with NMO or NMO spectrum disorders and 47 with MS. Seventeen subjects with NMO and all with MS had a remote history of optic neuritis (ON) in at least one eye, at least 6 months before OCT. Linear mixed modeling was used to compare the two diagnoses for a given level of vision loss, while controlling for age, disease duration, and number of episodes of ON.

Results: After ON, NMO was associated with a thinner mean RNFL compared to MS. This was found when controlling for visual acuity (56.7 vs 66.6 microm, p = 0.01) or for contrast sensitivity (61.2 vs 70.3 microm, p = 0.02). The superior and inferior quadrants were more severely affected in NMO than MS.

Conclusions: Optic neuritis (ON) within neuromyelitis optica (NMO) is associated with a thinner overall average retinal nerve fiber layer compared to multiple sclerosis, with particular involvement of the superior and inferior quadrants. This suggests that NMO is associated with more widespread axonal injury in the affected optic nerves. Optical coherence tomography can help distinguish the etiology of these two causes of ON, and may be useful as a surrogate marker of axonal involvement in demyelinating disease.

Figures

Figure 1 Average retinal nerve fiber layer thickness in multiple sclerosis vs neuromyelitis optica controlled for visual acuity Interquartile box plots demonstrate that the adjusted retinal nerve fiber layer is thinner in neuromyelitis optica for those eyes previously affected by optic neuritis (p = 0.01). Those categorized as normal had recovered to ≥20/25 from previous optic neuritis.

Figure 2 Retinal nerve fiber layer quadrant thickness in multiple sclerosis vs neuromyelitis optica controlled for visual acuity Interquartile box plots demonstrate that the adjusted superior (p < 0.01) and inferior (p = 0.03) retinal nerve fiber layer is thinner in neuromyelitis optica for those eyes previously affected by optic neuritis. MS = multiple sclerosis; NMO = neuromyelitis optica; VA = visual acuity.

Figure 3 Average retinal nerve fiber layer thickness in multiple sclerosis vs neuromyelitis optica controlled for contrast sensitivity Interquartile box plots demonstrate that median retinal nerve fiber layer is thinner in neuromyelitis optica for those eyes previously affected by optic neuritis (p = 0.02).

Figure 4 Retinal nerve fiber layer quadrant thickness in multiple sclerosis vs neuromyelitis optica controlled for contrast sensitivity Interquartile box plots demonstrate that the adjusted superior (p < 0.01), inferior (p = 0.03), and nasal (p = 0.03) retinal nerve fiber layer is thinner in neuromyelitis optica for those eyes previously affected by optic neuritis. MS = multiple sclerosis; NMO = neuromyelitis optica; CS = contrast sensitivity.