Walking While Talking: Relationships Among Motor-Cognitive Dual-Tasks, Functional Performance and Structural MRI

Background:  Greater than 45% of individuals with multiple sclerosis (MS) report cognitive dysfunction and 85% report gait dysfunction that interferes with daily functioning. Impairments in mobility and cognition contribute to declines in everyday activities that require simultaneous motor and cognitive functioning (e.g. motor-cognitive dual-tasks (MCDT)). Our lab has previously shown relationships among dynamic posturography and walking measures and among tract-specific measures of the brain corticospinal tract (CST) and walking measures in MS. 

Objectives: The objective of this study is to explore the relationships among motor function (i.e., posturography, walking), cognitive function, MCDT ability and tract-specific MRI measures.  

Methods: To date, 9 individuals with relapsing remitting MS have volunteered for this study (mean±SD age: 47.9±14.9 years; symptom duration: 11.1±6.1 years; gender: 7 females; EDSS median [range]: 2.5[1-4]). All subjects participated in motor and cognitive testing and a 3T MRI with both diffusion tensor (fractional anisotropy and mean diffusivity only) and magnetization transfer imaging. Correlation analyses were used to examine the relationships among clinical and MRI measures.

Results: Better performance on dynamic posturography (increased anterior-posterior (AP) sway) is related to improved walking performance (r>0.78; p<0.01). Interestingly, individuals with increased AP sway also had better diffusivity of (CST) (r=-0.86; p=0.003). Similarly, individuals with less sway on static balance testing (r=-0.70; p=0.036) and faster Timed Up and Go (TUG) performance demonstrated improved diffusivity of the CST (r=-0.67; p=0.048).  

Poorer performance on cognitive testing (Symbol Digit Modality Test) was associated with slower performance on MCDT (r>0.66; p<0.05). Additionally, individuals with less AP sway perform poorer on MCDT (r>0.76; p<0.02). Poor performance on balance dual-tasks was also associated with reduced diffusivity of the CST (r=-0.8667; p=0.0025). 

Conclusions: Our preliminary data suggests that assessment of MCDT may be a useful addition to the clinical exam as it provides information on both structural integrity and functional performance. Additionally, this work highlights the specificity of AP sway as a marker for walking function and provides new evidence of the relationship of dynamic posturography to MCDT performance and CST integrity. Future work will include exploration of additional brain tracts.