Similar Retinal Measurements Observed in Potential NMOSD and Definite NMOSD

A cross-sectional study showed that retinal measurements in patients with “potential” neuromyelitis optica spectrum disorder were similar to those with definite neuromyelitis optica spectrum disorder.

Nabil K. El Ayoubi, MD, neurologist, multiple sclerosis specialist, assistant professor of Clinical Specialty, American University of Beirut Medical Center

Nabil El Ayoubi, MD

In a cross-sectional optical coherence tomography (OCT) study on neuromyelitis optica spectrum disorder (NMOSD), retinal measurements in patients with “potential” NMOSD (pNMOSD) were comparable with participants with definite NMOSD (dNMOSD).1

Previous research before this study had not evaluated patients with a high clinical suspicion of NMOSD using retinal OCT, and these results suggest that OCT can differentiate when suspected NMOSD does not fulfill current diagnostic criteria. Between patients with pNMOSD and dNMOSD, all of the retinal measures were comparable, including ganglion cell/inner plexiform layer (GCIPL; ß= 2.27; P = .482), macular volume (MV; ß = 0.2; P = .298), peripapillary retinal nerve fiber layer (pRNFL; ß = 4.06; P =.464), macular retinal nerve fiber layer (mRNFL) ß = 0.48; P = 0.733), inner nuclear layer (INL; ß = 1.01; P = .36), and outer nuclear layer (ONL; ß = 0.6; P =.805).

Notably among patients with pNMOSD, all of the retinal measures were significantly lower compared with those with multiple sclerosis (MS) except for the ONL (GCIPL: ß = 7.06, P = 0.013; MV: ß = 0.57, P = .002; pRNFL: ß = 11.2, P = .019; mRNFL: ß = 3.65, P = .003; INL: ß = 1.9, P = .044) and compared with healthy controls (HCs) except for the ONL and INL (GCIPL: ß = 16.7, P <.0001; MV: ß = 0.95, P <.0001; pRNFL: ß = 19.9, P <.0001; mRNFL: ß = 5.54, P <.0001).

Primary investigator Nabil K. El Ayoubi, MD, neurologist, multiple sclerosis specialist, assistant professor of Clinical Specialty, American University of Beirut Medical Center, and colleagues noted from the subgroup analysis of eyes with history of optic neuritis (ON), “we found significant axonal loss in pNMOSD-related ON eyes that was similar to dNMOSD-related ON eyes and more pronounced than that of MS-related ON.”

The groups were compared at baseline for clinical and demographic characteristics, in addition to OCT measurements of pRNFL, INL, mRNFL, ONL, GCIPL, and MV. Patients’ data were collected between 2014 and 2019 from the AUB Multiple Sclerosis Interdisciplinary Research registry of the Nehme and Therese Tohme MS center at the American University of Beirut. Those with pNMOSD were defined by Ayoubi et al as patients with a high clinical suspicion of NMOSD but not fulfilling the current consensus diagnostic criteria.

Nighty-eight patients (dNMOSD, n = 17; pNMOSD, n = 20; MS, n = 70) and 22 HCs were included and evaluated. The different groups had similar history of ON (pNMOSD = 45.5%; dNMOSD = 35.3%; MS = 23%; between-groups differences, X2 = 3.05, df = 2, P = .218). The patients from the dNMOSD group (82.3%) were treated with rituximab (Rituxan; Biogen), as well as 72.7% of the those with pNMOSD at the time of the OCT scan. In the MS group, most patients (58.6%) were treated with fingolimod (Gilenya; Novartis) and the rest of the patients (41.4%) were given interferons.

El Ayoubi et al noted, “These findings remained significant after adjustment for age, gender, disease duration, and optic neuritis history, supporting the similarities between pNMOSD and dNMOSD regarding their retinal measures, as well as the potential usefulness of retinal OCT in the diagnosis of NMO spectrum disorders.”

The results in a subgroup analysis on the ON eyes (MS, n = 27; dNMOSD, n = 15; pNMOSD, n = 12) showed that pRNFL, mRNFL, GCIPL, INL, and MV were significantly lower in pNMOSD-related ON than MS-related ON (pRNFL: ß = 16.38, P = .007; mRNFL: ß = 5.09, P <.0001; GCIPL: ß = 17.5, P <.0001; INL: ß = 4.1, P <.0001; MV: ß = 1.18, P <.0001).

Greater Abnormal Visual Evoked Potential Found in NMOSD Than Idiopathic Demyelinating Optic Neuritis

“Our data suggest that OCT is a potentially useful tool to diagnose and correctly treat these patients, while differentiating them from MS. If our findings are replicated, then OCT may eventually be added to the consensus criteria and facilitate diagnosis of this challenging group,” El Ayoubi and colleagues wrote.

The study’s limitations included the sample size being small and that some patients were not tested for MOG IgG titers, meaning that they could have had a MOG-associated disease.1 Another limitation was that the study did not have available visual function testing scores.

El Ayoubi et al concluded, “Retinal OCT is a noninvasive tool that can be helpful in the diagnosis of cases with clinical suspicion of NMOSD but not fulfilling its current diagnostic criteria. If confirmed in larger studies, OCT could be added to support the NMOSD diagnostic criteria.” Also, retinal OCT be beneficial as a tool with helping to identify thinning in retinal layers patients with dNMOSD, the disease could be more widespread than seen on MRI scans and what is evident clinically.2

Future research should include longitudinal monitoring of patients with pNMOSD in larger studies for serology tests, MRI, and retinal OCTs since it could determine more accurately whether the retinal OCT measurements support a diagnosis of dNMOSD.

REFERENCES
1. Ayoubi NKE, Moussa H, Younes A, Haddad R, Khoury SJ. Use of retinal optical coherence tomography to differentiate suspected neuromyelitis optica spectrum disorder from multiple sclerosis: A cross-sectional study [published online ahead of print, 2022 Sep 7]. Mult Scler Relat Disord. 2022;68:104160. doi:10.1016/j.msard.2022.104160
2. Shen T, You Y, Arunachalam S, et al. Differing Structural and Functional Patterns of Optic Nerve Damage in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder. Ophthalmology. 2019;126(3):445-453. doi:10.1016/j.ophtha.2018.06.022
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