Correlations Between Pyramidal and Extrapyramidal (brainstem, cerebellar) FS Disability Scores with Mobility and Strength Performance in MS

Background: Links between neurological impairment and functional outcome measures are not well understood in Multiple Sclerosis (MS). Evaluation of sensitive, functional outcomes to measure disease progression and treatment efficacy besides neurological disability is essential. 

Objectives: This study correlated and compared pyramidal and extrapyramidal (brainstem, cerebellar) Functional System (FS) scores with mobility and strength performance in ambulatory individuals with MS. Significant predictors of pyramidal and extrapyramidal scores were determined from mobility and strength measures. 

Methods: Forty-six individuals with MS [36F/10M, mean (range): age (yrs)= 54.4 (23-74); Expanded Disability Status Scale, EDSS=3.9 (3.0-5.5); diagnosis duration (yrs)=15.3 (1-47)], no concurrent relapses were recruited from University of Utah MS Rehabilitation and Wellness Clinic database. Mobility was assessed by Berg Balance Test (BBT), Timed Up-and-Go (TUG), Stair-climbing Test (ST), six minute walk test distance, MS Walking Scale (MSWS), Activities-specific Balance Confidence (ABC), MS Functional Composite (MSFC; including 25-feet walk, 9-hole peg and paced auditory serial addition tests). Strength was measured by dynamometers for Hand Grip (Left, Right; HG-L, HG-R) and Knee Extensors (Left, Right; KE-L, KE-R). Standardized neurological assessment provided the pyramidal and extrapyramidal FS disability scores. Pearson correlations were calculated between pyramidal and extrapyramidal FS with mobility and strength separately. Significant correlations (r>0.35) were utilized to predict pyramidal and extrapyramidal FS scores. SPSS 20.0 was used for statistical analysis. 

Results: Pyramidal FS was significantly (p<0.05) correlated with KE-R (r= -0.343), KE-L (r= -0.313), MSFC (r= -0.424); brainstem FS with MSWS (r=0.404), TUG (r=0.401), ABC (r= -0.397), ST (r=0.412) and cerebellar FS with BBT (r=-0.607), HG-R(r=0.343), TUG (r=0.380), MSWS-12 (r=0.433), ABC (r=-0.319), MSFC (r=-0.404). Combined model of MSFC and KE, ST and BBT were found to be significant predictors of pyramidal, brainstem and cerebellar scores respectively.

Conclusions: Strong correlations between extrapyramidal FS and mobility scores suggest that performance on mobility tests (ST, BBT) provide more information about brainstem, cerebellar tract involvement in individuals with MS. Correlations between pyramidal FS and KE strength, MSFC indicate that these measures are more informative of pyramidal tract involvement in MS. These quick, quantitative measures of mobility and strength can prove to be useful for MS management and clinical research.