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.