OCT Retinal Imaging May Help Support Diagnosis of NMOSD
Optical coherence tomography could differentiate NMOSD from other diseases
Measuring the retinal nerve layers by a non-invasive tool called optical coherence tomography may help to diagnose neuromyelitis optica spectrum disorder (NMOSD), especially in those who test negative for disease-related antibodies, according to a new study.
Researchers found that nerve layers in the retina of people with NMOSD were significantly thinner than in those with multiple sclerosis (MS), a neurodegenerative disease in which the eyes can be affected. Thus, using optical coherence tomography (OCT) could help differentiate NMOSD from MS.
“Retinal OCT is a non-invasive tool that can be helpful in the diagnosis of cases with clinical suspicion of NMOSD but not fulfilling its current diagnostic criteria,” the researchers wrote. “If confirmed in larger studies, OCT could be added to support the NMOSD diagnostic criteria.”
The study, “Use of retinal optical coherence tomography to differentiate suspected neuromyelitis optica spectrum disorder from multiple sclerosis: a cross-sectional study,” was published in the journal Multiple Sclerosis and Related Disorders.
NMOSD is an autoimmune disorder characterized by inflammation most frequently affecting the optic nerve (optic neuritis) and/or the spinal cord (myelitis). People with the condition experience recurrent attacks separated by periods of remission.
Clinical symptoms and imaging analysis during NMOSD attacks can resemble other inflammatory autoimmune diseases affecting the brain and spinal cord, including MS, which is also associated with optic neuritis.
The cornerstone of NMOSD diagnosis is a blood test positive for NMOSD-related antibodies. However, up to 40% of cases test negative, making diagnosis more challenging. These patients, referred to as potential NMOSD (pNMOSD), can be misdiagnosed with myelitis, optic neuritis, chronic relapsing inflammatory optic neuritis, or even MS.
Therefore, new specific biomarkers are needed to distinguish NMOSD from MS and similar diseases.
What is optical coherence tomography?
OCT is a non-invasive imaging technology used to obtain images of the retina and has been widely used to measure the thickness of the optic nerves.
Researchers in Lebanon and the U.S. hypothesized that retinal OCT imaging could be used to distinguish NMOSD from MS.
To find out, the team recruited and tested 17 people with definite NMOSD (dNMOSD), 11 with pNMOSD, 70 individuals diagnosed with the relapsing-remitting form of MS, and 22 healthy controls. There were no significant differences in disease duration or the proportion of eyes with a history of optic neuritis among patients.
Blood tests showed seven of the 17 individuals with a definite NMOSD diagnosis were positive for NMOSD-related antibodies, whereas all potential cases tested negative.
Antibody-suppressant rituximab (sold as Rituxan, among others), commonly used off-label in NMOSD, was given to 14 in the dNMOSD group (82.3%) and eight in the pNMOSD group (72.7%). MS patients were receiving immune-modulating fingolimod and interferons.
OCT measured the thickness of the different layers of nerves within the retina, including the peripapillary retinal nerve fiber layer, inner nuclear layer, macular retinal nerve fiber layer, outer nuclear layer, and the ganglion cell/inner plexiform layer. The volume of the macula, the functional center of the retina, was also measured.
The analysis revealed all retinal measurements were significantly smaller among individuals with pNMOSD compared to MS patients except for the outer nuclear layer. The same was found comparing pNMOSD to controls, except for the outer and inner nuclear layers. All measures were comparable between potential and definite NMOSD patients.
The team found similar results in the eyes of patients with a history of optic neuritis, including 27 eyes from MS patients, 15 dNMOSD eyes, and 12 pNMOSD eyes. Again, nearly all measures were significantly thinner in pNMOSD-related optic neuritis than MS-related optic neuritis.
Consistently, all measurements were comparable between the definite and potential NMOSD groups, except the inner nuclear layer in potential cases was significantly lower.
These differences remained significant after adjusting for age, sex, 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 researchers wrote.
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