“Expanded Disability Status Scale 0 is not normal”

High-challenge tests can reveal performance differences between healthy controls and MS patients with an Expanded Disability Status Scale (EDSS) score of 0. Correlations between challenge task performance and imaging markers (T2LV and nThal) encapsulate both lesional burden of disease and a volumetric measure of brain reserve [1].

Detection of MS in the early stages is complicated due to the absence of above-threshold symptoms. Sub-threshold MS lesions are compensated by functional reserve and yield no physical deficits. The threshold above which clinical deficits are recognised depends on the sensitivity of the assessment techniques. The widely used EDSS defines a score of 0 as ‘neurologically normal.’

“We are only as sensitive as our tests allow,” Dr Stephen Krieger (Mount Sinai Hospital, NY, USA) explained. “The recent concept of silent progression has been highly discussed. But it is only silent if we are not listening.” Recognition of sub-threshold deficits in apparently neurologically normal MS patients may help to better understand and predict the disease course. Dr Krieger and his colleagues hypothesised that higher-challenge tasks may be more sensitive to sub-threshold deficits, with neuroimaging correlates. “Patients with an EDSS score of 0 should be the same as healthy controls, but are they?”

To answer this question, 63 recently (<5 years) diagnosed MS patients in the RADIEMS cohort with an EDSS of 0 were compared with 50 matched healthy controls on standard tasks, including the timed 25-foot walk (T25FW) and high-challenge measures of upper extremity coordination (9-Hole Peg, Grooved Pegboard) and balance (NIH Toolbox Balance, Balance Boards).

Results showed that patients with an EDSS score of 0 also had normal T25FWs (median 3.95; interquartile range 3.75–4.24). However, patients performed worse than controls on:

• upper extremity (P=0.039);
• balance (P=0.005);
• overall function (P=0.006).

The higher overall function was associated with lower T2 lesion volume (T2LV; r=-0.344; P=0.006) and higher normalised thalamic volume (nThal; r=0.461; P<0.001). Dr Krieger concluded: “These results show that EDSS 0 is not normal. This challenges the existing dogma of how we define MS severity right from the beginning.” He added that correlations between challenge task performance and imaging markers (T2LV and nThal) encapsulate both lesional burden of MS and a volumetric measure of brain reserve.

1. Krieger S, Sumowski J. Subclinical burden of multiple sclerosis at EDSS 0. OP122, ECTRIMS 2021 Virtual Congress, 13–15 October.

 

Copyright ©2021 Medicom Medical Publishers



Posted on 9 December 20219 December 2021