Spectral Domain Optical Coherence Tomography May Help Diagnose Neuromyelitis Optica
Christin L. Melton, ELS
Washington, DC—Research presented in a poster at the 67th Annual Meeting of the American Academy of Neurology found that the thickness of the macular parafoveal layer of the retina may be useful for distinguishing between neuromyelitis optica (NMO) and multiple sclerosis (MS) in patients who present with neurodegenerative retinal disease.1 Demyelinating optic neuritis can occur with either inflammatory autoimmune condition, and several studies have examined whether differences in macular thickness can be used to pinpoint the underlying cause of optic neuritis. The distinction is important because NMO and MS typically require different courses of treatment.
Optical coherence tomography (OCT) is used to identify retinal abnormalities and patterns of axonal degeneration or neuronal loss in patients with NMO, MS, and other diseases known to affect the anterior optic pathway. The authors of the current study noted that unlike previous studies, which primarily used OCT to measure overall macular thickness, they used spectral domain (SD)-OCT and measured inner retinal layers that had were first separated using an automated segmentation algorithm.1
The study included 14 patients with NMO and 14 patients with MS. Using SD-OCT, the research team determined the volume and mean parafoveal thickness of the macula and of 6 inner retinal layers. Data for the groups of NMO and MS patients were compared with data for a group of healthy controls.1
The researchers found that the NMO group had significantly more thinning of the total retina than the MS group. The NMO group also had a significantly thinner ganglion cell layer and inner plexiform layer than the MS group, which the researchers said was consistent with findings from the few studies that have also examined inner retinal layers.
The current study showed no statistically significant differences between the groups in the thickness of the inner nuclear layer, the macular retinal nerve fiber layer, or in any outer retinal layers. In contrast, previous studies have reported significant differences between the inner nuclear layer in patients with NMO vs MS. Müller cells, which express aquaporin-4, are located in the inner nuclear layer of the retina, and it has been hypothesized that anti-aquaporin-4 antibodies might affect the thickness of this layer in NMO patients.2 However, when the research team stratified patients by NMO antibody status, the results were unchanged.1
Patients were considered to have NMO when the thickness of their macular parafoveal layer fell below the 5th percentile of macular parafoveal layer thickness in healthy controls. Applying this threshold showed that SD-OCT had 58% sensitivity and 77% specificity for identifying NMO disease.
1. Loeb R, Finch A, Javed A, Bernard J. Retinal segmentation distinguishes neuromyelitis optica from multiple sclerosis using optical coherence tomography regardless of antibody status. Poster presented at: 67th Annual Meeting of the American Academy of Neurology; April 18-25, 2015; Washington, DC. Abstract I1-5A.
2. Fernandes DB, Raza AS, Nogueira RG, et al. Evaluation of inner retinal layers in patients with multiple sclerosis or neuromyelitis optica using optical coherence tomography. Ophthalmology. 2013;120(2):387-394.