Do we need to include cognition as a treatment target in multiple sclerosis?
In every clinic, I do patients with MS complain of cognitive symptoms. Either it is increasing forgetfulness, difficult multi-tasking, the inability to learn and use a new technology or cognitive fatigue.
Case study: One of my high functioning patients, who worked in a large City law firm, simply could not keep up and was recently forced to take early retirement because of her MS. She had been interferon-beta-1b for 12 years but had stopped treatment about 7 years ago when she had moved to London. Her MRI showed a highish lesion load and severe brain atrophy. She had had a few relapses on interferon-beta in the early years, but her neurologist decided to leave her on interferon-beta. Back then this was normal practice; we didn’t expect interferon-beta to render you relapse-free. Interferons were only meant to reduced attack rates by about a third and severe attacks, i.e. those requiring steroids and/or hospital admission, by about a half. The only alternative when this patient was having relapses on interferon-beta was glatiramer acetate; please remember this was pre-natalizumab era. Apart from her cognitive problems, this patient had mild unsteadiness of gait, but this had not affected her walking distance and she was still able to do yoga several times per week. To help with her unemployment insurance claim I requested a formal neuropsychological assessment and she was documented to have profound cognitive deficits across multiple domains. The conclusion based on these tests was that she would never be able to have meaningful employment again; at least not in the knowledge economy When I took a detailed history it was clear that she had had progressive cognitive impairment over at least 7-10 years. In other words, she had secondary progressive MS manifesting as progressive dementia.
You must not underestimate the impact MS has on cognition. Cognitive problems can be there from the start; approximately a quarter of people with a radiologically isolated syndrome (RIS) or asymptomatic MS already have cognitive impairment. The proportion with cognitive impairment just gets higher the longer you have the disease. What is driving cognitive impairment is almost certainly grey matter pathology, both in the cortex and deep grey matter, which is not detected with our current monitoring tools.
In the analysis below, of the pivotal phase 3 fingolimod trials, we showed that not being able to improve on the Paced Auditory Serial Addition Test (PASAT) at baseline predicted a worse outcome. The PASAT is a very sensitive cognitive test that used to part of the battery we called the MS Functional Composite (MSFC). The PASAT is not very nice to do and has now been replaced by the SDMT (symbol digital modality test).
When you start doing cognitive screening tests such as the PASAT and SDMT you tend to improve the scores due to a learning effect. We hypothesised that pwMS who couldn’t learn i.e. were unable to improve their PASAT scores at baseline would do worse. This is exactly what we found and we noted it regardless of treatment allocation; i.e. whether you were on fingolimod or placebo. Poor learners were older, had a higher disability score at baseline, smaller brains and higher lesions volumes on MRI; i.e. they had reduced cognitive reserve. The depressing point about this analysis was that even the poor learners on fingolimod did badly; it was if they were already primed to do badly and that starting a DMT had a limited impact on the outcome. Active MS in the past had primed their brains to continue deteriorating; previous damage or a new type of MS lesion, possibly SELs (slowly expanding lesions) was driving their worsening.
The message here is that it is very important to prevent the ravages of MS by treating as early and effectively as possible. In some pwMS, this is easy because you present early before too much damage has accrued. In others, you may have longer asymptomatic periods during which you have already acquired a lot of damage. Regardless of what group you are in, you need to seriously consider getting on top of your MS disease activity as soon as possible to prevent further damage.
It is clear from the Sormani meta-analysis (article 2 below) that you do best on DMTs that have the greatest impact on inflammatory activity (new MRI lesions) and those that reduce brain volume loss the most. This is why flipping the pyramid and going for the most effective DMTs first-line is a very appealing treatment strategy; particularly those that ‘normalise’ brain volume loss.
This study also raises the question about whether or not we should be monitoring cognition in routine clinical practice? This topic is a hot potato and gets discussed and debated all the time. At the moment I think most neurologists don’t agree with doing routine cognitive testing, because of the lack of evidence in terms of treatments that impact on cognition. This, however, may change when siponimod gets licensed. It is clear in the siponimod trial that siponimod delayed cognitive worsening compared to placebo. The following is the siponimod data that was presented at the AAN and EAN last year.
I believe that everyone with MS should have the option of monitoring their own cognition. If your cognition is improving and/or is stable that is good news. If, however, cognition is worsening then a frank discussion needs to be had about why it is getting worse and can anything be done about it. There are many reasons why pwMS may have worsening cognition and some of these are treatable. This is why we have developed an online cognitive test, which we are currently validating, to allow self-monitoring of cognition. If you had access to the test would you use it?
Sormani et al. Learning ability correlates with brain atrophy and disability progression in RRMS. J Neurol Neurosurg Psychiatry. 2019 Jan;90(1):38-43.
OBJECTIVE: To assess the prognostic value of practice effect on Paced Auditory Serial Addition Test (PASAT) in multiple sclerosis.
METHODS: We compared screening (day -14) and baseline (day 0) PASAT scores of 1009 patients from the FTY720 Research Evaluating Effects of Daily Oral therapy in Multiple Sclerosis (FREEDOMS) trial. We grouped patients into high and low learners if their PASAT score change was above or below the median change in their screening PASAT quartile group. We used Wilcoxon test to compare baseline disease characteristics between high and low learners, and multiple regression models to assess the respective impact of learning ability, baseline normalised brain volume and treatment on brain volume loss and 6-month confirmed disability progression over 2 years.
RESULTS: The mean PASAT score at screening was 45.38, increasing on average by 3.18 from day -14 to day 0. High learners were younger (p=0.003), had lower Expanded Disability Status Scale score (p=0.031), higher brain volume (p<0.001) and lower T2 lesion volume (p=0.009) at baseline. Learning status was not significantly associated with disability progression (HR=0.953, p=0.779), when adjusting for baseline normalised brain volume, screening PASAT score and treatment arm. However, the effect of fingolimod on disability progression was more pronounced in high learners (HR=0.396, p<0.001) than in low learners (HR=0.798, p=0.351; p for interaction=0.05). Brain volume loss at month 24 tended to be higher in low learners (0.17%, p=0.058), after adjusting for the same covariates.
CONCLUSIONS: Short-term practice effects on PASAT are related to brain volume, disease severity and age and have clinically meaningful prognostic implications. High learners benefited more from fingolimod treatment.
Sormani et al. Treatment effect on brain atrophy correlates with treatment effect on disability in multiple sclerosis. Ann Neurol. 2014 Jan;75(1):43-9.
OBJECTIVE: To evaluate the extent to which treatment effect on brain atrophy is able to mediate, at the trial level, the treatment effect on disability progression in relapsing-remitting multiple sclerosis (RRMS).
METHODS: We collected all published randomized clinical trials in RRMS lasting at least 2 years and including as endpoints disability progression (defined as 6 or 3 months confirmed 1-point increase on the Expanded Disability Status Scale), active magnetic resonance imaging (MRI) lesions (defined as new/enlarging T2 lesions), and brain atrophy (defined as change in brain volume between month 24 and month 6-12). Treatment effects were expressed as relative reductions. A linear regression, weighted for trial size and duration, was used to assess the relationship between the treatment effects on MRI markers and on disability progression.
RESULTS: Thirteen trials including >13,500 RRMS patients were included in the meta-analysis. Treatment effects on disability progression were correlated with treatment effects both on brain atrophy (R(2) = 0.48, p = 0.001) and on active MRI lesions (R(2) = 0.61, p < 0.001). When the effects on both MRI endpoints were included in a multivariate model, the correlation was higher (R(2) = 0.75, p < 0.001), and both variables were retained as independently related to the treatment effect on disability progression.
INTERPRETATION: In RRMS, the treatment effect on brain atrophy is correlated with the effect on disability progression over 2 years. This effect is independent of the effect of active MRI lesions on disability; the 2 MRI measures predict the treatment effect on disability more closely when used in combination.