Mark Gudesblatt, MD
LONDON—The Expanded Disability Status Scale (EDSS) is largely insensitive to cognitive ability in patients with multiple sclerosis (MS) and does not comprehensively capture accumulated cognitive disability, according to research presented at the 32nd Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS). “The EDSS’s use as the gold standard in measuring accumulated disability in patients with MS should be reconsidered as cognitive impairment–related disability can occur independent of EDSS,” said Mark Gudesblatt, MD, Medical Director of the Comprehensive MS Care Center at South Shore Neurologic Associates in Islip, New York.
MS is typically measured by MRI changes, relapse rates, and EDSS. Changes in EDSS score are primarily driven by motor and walking impairment. According to Dr. Gudesblatt and colleagues, cognitive impairment, independent of EDSS, in patients with MS impacts employment, driving, fall risk, and quality of life. “Although the EDSS is universally accepted to measure treatment efficacy, cognitive function does not impact EDSS. Cognitive function greatly varies independently of walking ability and is an important aspect of disease impact for patients with MS,” Dr. Gudesblatt said.
To investigate the sensitivity of the EDSS in measuring cognitive ability in patients with MS, Dr. Gudesblatt and colleagues asked a group of patients with MS to complete a computerized cognitive assessment battery (NeuroTrax) with analysis of cognitive domain scores (ie, memory, executive function, visual spatial, and verbal function, attention, information processing, and motor skills). The average of these domain scores was defined as the global cognitive score. The number of cognitive domains impaired greater than one standard deviation from age- and education-matched norms were also recorded for each assessment battery. A certified grader assigned EDSS scores to participants at the date of their cognitive testing. EDSS groups were defined as low (EDSS 0 to 2.5), moderate (EDSS 3 to 4.5), high (EDSS 5 to 6.5), and severe (EDSS > 7). Percent overlap of NeuroTrax cognitive scores were calculated across EDSS both adjacent (low and moderate, moderate and high, high and severe) and extreme (low and severe) groups.
A total of 258 patients with MS were enrolled in the study; 72.5% were women and the average age was 46.2. For the global cognitive score in patients with MS, there was an average 65% overlap across adjacent EDSS groups and a 42.5% overlap across extreme EDSS groups. The overlap of the cognitive domain scores were: memory (65.3% average adjacent, 65.3% extreme), executive function (65.1% average adjacent, 35.1% extreme), attention (60.3% average adjacent, 38.1% extreme), information processing speed (58.0% average adjacent, 42.5% extreme), visual spatial (65.6% average adjacent, 63.2% extreme), verbal function (70.1% average adjacent, 66.4% extreme), motor skills (55.2% average adjacent, 32.3% extreme). The overlap of number of cognitive domains impaired one standard deviation or more below the normative means was 72.2% across EDSS adjacent groups and 38.1% across extreme EDSS groups.
—Glenn S. Williams