Oval-Shaped Masses More Prevalent in Eyes of NMOSD Patients: Study
PHOMS occurrence in NMOSD, MOGAD not linked to history of optic neuritis
Adults with neuromyelitis optica spectrum disease (NMOSD) who are positive for antibodies against the aquaporin-4 (AQP4) protein have a higher prevalence of oval-shaped masses surrounding the optic nerve in their eyes than healthy people, a study showed.
Although these masses were significantly linked to older age, their occurrence was not related to differences in sex, disease severity or duration, or a history of optic neuritis — an inflammation of the optic nerve that’s a common NMOSD symptom.
Similar results were seen in adults with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), a similar autoimmune condition that also causes optic neuritis.
The study, “Peripapillary hyper-reflective ovoid mass-like structures (PHOMS) in AQP4-IgG-positive neuromyelitis optica spectrum disease (NMOSD) and MOG-IgG-associated disease (MOGAD),” was published in the Journal of Neurology.
Optic neuritis in NMOSD is due to abnormal immune attacks against proteins in cells that support the nervous system. These attacks most commonly involve antibodies against the AQP4 water channel protein.
Since the optic nerve sends visual information from the eyes to the brain, optic neuritis can result in eye pain and blurry or lost vision.
Optical coherence tomography (OCT) is a noninvasive imaging method that takes cross-section pictures of the back of the eye, including the retina, or the innermost, light-sensitive eye layer, and the optic nerve.
In 16–18% of people with multiple sclerosis (MS), an autoimmune disease that commonly causes optic neuritis, OCT revealed abnormal masses called peripapillary hyper-reflective ovoid mass-like structures (PHOMS).
PHOMS are oval-shaped masses with highly reflective edges in the peripapillary region, the area of the back of the eye surrounding the optic nerve. They’re thought to be associated with problems in the movement of molecules and cellular structures across nerve fibers and/or congestion in the system that regulates cerebrospinal fluid (CSF) flow. CSF is the liquid surrounding the brain and spinal cord.
Little is known about PHOMS prevalence in people with NMOSD and other similar conditions affecting the optic nerve, as well as in healthy people, however.
Evaluating PHOMS’ presence in NMOSD, MOGAD
Investigators at the Ludwig-Maximilians University Munich, Germany conducted an OCT examination in 47 NMOSD patients positive for anti-AQP4 antibodies (83% women; mean age, 53) and 44 MOGAD patients (54.6% women; mean age, 37).
An OCT examination was also done in 55 healthy people who were used as controls, 46 of whom were matched to NMOSD patients on age and sex, while 35 were age- and sex-matched to MOGAD patients.
Because optic neuritis can affect the retina, OCT was also used to measure retinal layers in NMOSD and MOGAD patients without a history of this inflammation.
Results showed PHOMS were detected in eight of the 47 NMOSD patients (17%), covering 11 of the 89 eyes evaluated (12%). Only two matched controls (4.3%) had PHOMS in three of the 94 eyes assessed (3%). This difference failed to reach statistical significance.
Statistical analysis found PHOMS-positive NMOSD patients were significantly older than those without PHOMS. However, no other significant differences were seen between NMOSD patients with or without PHOMS, including in disease duration, severity, or optic neuritis history.
There were no significant differences in any retinal layer when comparing NMOSD patients with and without PHOMS or between patients and controls in eyes without a history of optic neuritis.
Also, a greater proportion of MOGAD patients had PHOMS relative to their matched controls (14% vs. 5.6%), but this difference also failed to attain statistical significance. There were no significant differences in demographic or clinical parameters between MOGAD patients with or without PHOMS.
Retinal scans of MOGAD patients’ eyes without a history of optic neuritis showed two retinal measures that were significantly reduced compared with controls, but no significant differences were detected between MOGAD patients with and without PHOMS.
These findings highlight that in both AQP4-positive NMOSD and MOGAD groups, “the proportion of patients with PHOMS was comparable to previously published data on PHOMS prevalence in MS,” the researchers wrote.
As such, “a disease-specific occurrence is unlikely, but a disease-dependent occurrence can be assumed with a higher prevalence of PHOMS compared to [healthy controls],” they said. “A dedicated examination for PHOMS in different disease groups is useful, especially since the presence of PHOMS could also be mistakenly classified as papilledema [optic nerve swelling] in the ophthalmological examination,” the researchers wrote, noting PHOMS occurrence “was not associated with sex, disease duration, disability and retinal [damage].”
Larger, international studies following patients over time are needed to confirm the findings, they said.