Seasonal patterns and subtle differences in relapse identify NMOSD

Multiple sclerosis

By Mardi Chapman

9 Jul 2020

Professor Simon Broadley

Relapse in neuromyelitis optica spectrum disorders (NMOSD) appears to peak during mid-spring and summer, according to an Australian and New Zealand study.

The seasonal effect on relapses is one of the novel findings of subtle difference from the retrospective case-control study of 75 NMOSD patients and 101 MS patients from 23 centres.

The study found the annualised relapse rate in NMOSD was approximately double that of MS controls (0.77 v 0.33; p<0.001) and the types of relapses were also different.

Optic neuritis was more common in NMOSD than MS as a first relapse (38% v 12%; p<0.001) and across all relapses (40% v 16%; p<0.001).

Area postrema syndrome was more common in NMOSD than MS patients in first (9% v 0%; p=0.009) and all relapses (3% v 0%; p=0.002) while other brainstem syndromes were seen more frequently in MS in first (4% v 25%; p<0.001) and all relapses (5% v 24%; p<0.001).

Another new finding was that while relapses of all types were seen across a broad range of ages, optic neuritis predominated at a younger age of 20–29 years while transverse myelitis was more common at 40–49 years.

The study found the time between relapses was shorter in NMOSD than MS (10.6 v 18.0 months), relapse duration was longer (68 v 50 days) and maximal disability levels were also higher (EDSS 4 v 3).

Patients with NMOSD were less likely to make a complete recovery than MS patients (29% v 56%; p<0.001).

Relapses in NMOSD were more likely to be treated with high dose IV or oral steroids, plasma exchange and IV immunoglobulin than relapses in MS.

The study authors said the distinct patterns of relapse might further assist in the early identification of cases of NMOSD and provide information about potential trigger factors.

Senior investigator and neurologist Professor Simon Broadley, from Griffith University, told the limbic AQP4 antibody testing had led to a big improvement in diagnosis.

“In the past, a good 50% or more of what we now recognise to be NMOSD were previously diagnosed as MS. But now with ready access to the antibody that is probably much less common.”

“A new problem is that having now recognised this different pattern, we are much more tuned into it and we recognise there are these people who have probably got something different but their antibodies are negative and we don’t know what they’ve got.”

“There is definitely a big grey zone which is probably almost as many people as who actually have NMOSD. We are still trying to work out what to do with those people.”

He said the paper highlights the mostly subtle ways in which NMOSD relapses differ from regular MS.

“The bottom line is there is a lot of overlap but the pattern is just slightly different and people need to be aware of that. And there are some things that you only see in NMOSD and you don’t see in MS.”

“We’ve shown that there probably is some seasonal variation which is actually not that dissimilar to MS so there are clearly factors out there that can influence the risk of relapse in both MS and in NMOSD and they may be the same. We don’t know that yet of course.”

Professor Broadley said the paper also confirmed the need to treat relapses early using combinations of steroids and plasma exchange.

“There have now been four well-conducted clinical trials for this condition, with very effective therapies, so treatment-wise things are improving. The next really big question is trying to find out what causes it and what are those factors that influence it.”

He added that he was part of a team trying to put together a worldwide epidemiological study of NMOSD.

“The obvious factors in MS are genetics, vitamin D, sun exposure, obesity – it’s going to have to be those same or similar things but like a lot of autoimmune diseases I suspect it is going to turn out to be complicated. It’s not one single factor.”

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