The Symbol Digit Modalities Test is an effective cognitive screen in pediatric onset multiple sclerosis (MS).

OBJECTIVE To evaluate the Symbol Digit Modalities Test (SDMT) as a tool for identifying pediatric-onset MS patients at risk for cognitive impairment. BACKGROUND The SDMT is a brief measure of cognitive processing speed that is often used in adult MS patients. Approximately one-third of pediatric-onset MS patients have cognitive impairment and there is a need for an effective screening instrument. DESIGN/METHODS Seventy (70) consecutive outpatients with pediatric-onset MS underwent clinical evaluations including the SDMT and were compared to those with other pediatric neurological diagnoses (OND, n=40) and healthy controls (HC, n=32). A subset of the MS group and all healthy controls completed neuropsychological evaluation within one year of SDMT administration. RESULTS The MS group performed worse on the SDMT compared to the HC group (p=0.02). Thirty-seven percent (37%) of the MS, 20% of the OND, and 9% of HC groups scored in the impaired range. For MS participants who underwent neuropsychological testing (n=31), the SDMT showed 77% sensitivity and 81% specificity for detecting neuropsychological impairment when administered within one year and reached 100% sensitivity when the interval was under two months (n=17). Overall, older age and increased disability predicted poorer SDMT performance (age r=-0.26, p=0.03) and the Expanded Disability Status Scale score or EDSS (r=-0.47, p<0.001), while a history of optic neuritis predicted better performance (p=0.04). Optical coherence tomography measures were not related to SDMT performance. CONCLUSION In this preliminary study, the SDMT was an effective brief screen for detecting cognitive impairment in pediatric-onset MS.