Symbol Digit Modalities Test Is More Sensitive Than Pasat to Demonstrate the Correlation Between Cognitive Impairment and Walking Disability

Background: Cognitive deficit can be an early feature in the course of multiple sclerosis. One of the most common cognitive impairments documented based on neuropsychological testing in MS involves cognitive processing speed. The Multiple Sclerosis Walking Scale-12 (MSWS-12) has been a commonly used patient reported outcome for measuring walking impairment in research involving multiple sclerosis (MS). MSWS-12 has been a commonly used patient-reported outcome based on the strength and breadth of evidence for the construct validity of its scores. The evidence for its construct validity is largely based on associations with other ambulatory-based outcomes such as timed 25-foot walking (T25FW), and EDSS. Performance on measures of prossessing speed, particularly the SDMT and PASAT, has been associated with walking outcomes in MS patients.

Objectives: The aim of the present study was to investigate the relationship between cognitive impairment and walking disability

Methods: 71 MS patients (54 female) who completed the MSWS-12, underwent a neurological examination, and completed the Symbol Digit Modalities Test (SDMT), Paced Auditory Serial Addition Test (PASAT), and Timed 25-Foot Walk (T25FW).

Results: The SDMT was significantly correlated with MSWS-12 scores (r=-0.602, p=0.002) and T25FW (r=-0.512, p=0.016), and Expanded Disability Status Scale (EDSS) (r=-0.368, p=0.042). The PASAT was also significantly correlated with MSWS-12 (r=-0.455, p=0.008), T25FW (r=-0.360, p=0.045). There was no significant correlation between PASAT and EDSS (p=0.0124, p=0.074). There were statistically significant correlations between MSWS-12 and T25FW (r=0.690, p=0.001), and EDSS (r=0.896, p=0.000).

Conclusions: Our results demonstrated that both SDMT and PASAT were correlated with walking impairment. SDMT seems to be more sensitive than PASAT regarding demonstration the correlation between cognitive impairment and walking disability.