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Is a Unidimensional Cognitive Screen Sufficient for Patients With MS?

A unidimensional approach to evaluating cognitive deficits misses the variability and impact of the disease.


BERLIN—Cognitive impairment in patients with multiple sclerosis (MS) varies in presence and degree in a manner that is neither identified nor quantified by the Symbol Digit Modalities Test (SDMT), according to a study presented at ECTRIMS 2018. “A unidimensional score or measure is insufficient to adequately identify and appreciate the richness and variation of the combinations and degrees of cognitive impairment that occur in patients with MS and impact the appearance of meaningful cognitive-related disability,” said Mark Gudesblatt, MD, Medical Director of the Comprehensive MS Care Center at South Shore Neurologic Associates in Islip, New York, and colleagues. “Better screening tools are required for evaluation of cognitive impairment in patients with MS.”

Mark Gudesblatt, MD

Cognitive impairment is common in people with MS. This impairment impacts economically important milestones and patient quality of life. Clinician and patient perceptions of the presence and degree of cognitive impairment are insufficiently sensitive measures, according to Dr. Gudesblatt. An increasing number of cognitive domains impaired greater than 1 standard deviation below age- and education-matched persons with MS has been shown to progressively impact self-reported driving, employment, and fall risk in patients with an EDSS score less than 6. Important cognitive disability in patients with MS can be unrelated to visible physical disability. Variability in the location and degree of MS plaque burden may differentially affect cognitive and physical ability, and many other factors may influence cognitive impairment in patients with MS. Routine cognitive screening in MS care is uncommon, Dr. Gudesblatt said. The SDMT, although frequently recommended, provides a single screening score that does not provide information about individual cognitive domains or the presence and degree of impairment across multiple cognitive domains or the accumulation of cognitive impairment.

Dr. Gudesblatt and colleagues conducted a retrospective review of consecutive patients with MS referred for screening with a multidomain computerized screening cognitive assessment battery (CAB) in the course of routine care who also underwent testing with the oral version of the SDMT on the same day. Their study included 113 patients with MS. The cohort had a mean age of 48.9, and 85% were female.

Within this patient sample, the SDMT defined cognitive function as follows: 68% normal classification, 14% low, 5% moderately low, and 12% very low. In this same patient group, the multidomain screening CAB identified the following domains of cognitive impairment greater than 1 standard deviation below normal values: memory (32%), executive function (25%), attention (28%), information processing speed (30%), visuospatial processing (20%), verbal function (23%), motor skills (20%), and a global summary screening score (24%). The multidimensional screening CAB in this same patient population further identified the number of cognitive domains impaired: zero domains, 36%; one domain, 24%; two domains, 11.5%; and three or more domains, 28%.

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