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Neurol Sci. 2017 Apr;38(4):635-642. doi: 10.1007/s10072-017-2813-0. Epub 2017 Jan 11.

The computer-based Symbol Digit Modalities Test: establishing age-expected performance in healthy controls and evaluation of pediatric MS patients.

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Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Canada.
Division of Child Neurology, Department of Pediatrics, The University Children's Hospital, University of Bern, Freiburgstrasse 15, 3010, Bern, Switzerland.
Departments of Internal Medicine and Community Health Sciences, University of Manitoba, Winnipeg, Canada.
Department of Psychology, York University, Toronto, Canada.
Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Canada.
Department of Psychiatry, University of Toronto, Toronto, Canada.
The Children's Hospital of Philadelphia, Perelman School of Medicine, University of Philadelphia, Philadelphia, PA, USA.


Decreased information processing speed (IPS) is frequently reported in pediatric multiple sclerosis (MS) patients. The computerized version of the Symbol Digit Modalities Test (c-SDMT) measures IPS over eight consecutive trials per session and additionally captures changes in performance within the session. Here, we establish normative c-SDMT performance and test-retest reliability in healthy children (HC) and explore differences in the overall c-SDMT-performance between HC and MS patients. This cross-sectional study included 478 HC (237 female, 49.5%) divided into five age groups (2 years each), and 27 MS patients (22 female, 81.5%) aged 8-18 years. The average time to complete the c-SDMT increased with age (|r| 0.70, 95% CI -0.74, -0.64). Test-retest reliability was high (ICC = 0.91) in HC. The total time to complete the c-SDMT did not differ between children with MS and sex- and age- matched HC (p = 0.23). However, MS patients were less likely to show faster performance across all the successive eight trials compared to HC (p = 0.0001). Healthy children demonstrate faster IPS with increasing age, as well as during successive trials of the c-SDMT. The inability of pediatric MS patients to maintain the increase in processing speed over successive trials suggests a reduced capacity for procedural learning, possibly resulting from cognitive fatigue.


Neurocognition; Pediatric MS; Processing speed; Symbol Digit Modalities Test

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