Cognitive impairment screening in multiple sclerosis using the Symbol Digit Modalities Test in a group of patients from the northeast region of Brazil

Introduction: Cognitive impairment (CI) is a common and disabling complication of multiple sclerosis (MS) The Symbol Digit Modalities Test (SDMT) is a brief measure of cognitive processing speed which is often used in adult MS patients, and, over the last 5 years, it has become the most commonly used neuropsychological test of processing speed in MS. Objective: To assess CI in multiple sclerosis (MS) patients using SDMT-oral version and correlate it with EDSS and Timed Walk Test (TWT). Methods: Seventy-four (74) consecutive outpatients with MS underwent clinical evaluations including SDMT-oral version during regular visits between the years 2022 and 2023. Patient’s data were converted to z-scores based on control data (Arq Neuropsiquiatr. 2018 Mar;76(3):163-169) and were classified as impaired if they performed in ?1,5 below normal controls). Correlation between SDMT and patient’s disability scales were assessed using the Spearman correlation test. Results: A total of 74 MS patients were included (21 males, 53 females). Mean age was 39,18 (SD 10.43) and distribution according to clinical forms was: RRMS=54 (73.9%), SPMS=16 (21.6%), PPMS=4 (5.4%). Mean of EDSS was 2.25 (SD 2.34). Mean of Timed Walk was 10.78 (SD 15.75). Mean of SDMT was 32.5 points (SD = 15.75). Around 29 (39,18%) of patients exhibited a result below the aggregate mean of normal controls. Regarding the disability scale and the SDMT, a moderately correlation was established for EDSS (r= -0.5569; P < 0,0001) and for TWT (r= -0.4347; P= 0,002), but the correlation was weak with age (r= -0.2354; p=0,044), disease duration (r= -0.3897; p=0.0009) and education level (r= 0.3997; p= 0,0007). Conclusion: As the SDMT is an easy, low-cost and fast test, this result may help to detect CI in daily clinical practice. The present study has shown SDMT is moderately correlated with EDSS and TWT.