Is there a link between ultrasonography measurements of thigh muscles, clinical and isokinetic parameters in MS patients?

Abstract

The aim of the study was to investigate the relations between ultrasound measurements of thigh muscles, isokinetic muscle strength and clinical parameters in a sample of multiple sclerosis (MS) patients. We included 12 adult MS patients with a significant disability (EDSS: 5.2 ± 1.5). We assessed ultrasound measurements of vastus lateralis (VL) and biceps femoris (BF), with computer image processing (thickness, pennation angle and fascicle length). The muscle strength was assessed with isokinetic dynamometry for both VL and BF (muscle peak torque in N·m −1 ) We also recorded clinical parameters such as spasticity (Ashworth scale), gait speed and fatigue (Fatigue Severity Scale). All the parameters were recorded twice: at the baseline and after three weeks of follow-up and muscle-strengthening in a neurological rehabilitation hospitalization unit. The weakest muscle of both was used in the analysis for a better clinical accuracy. A linear Pearson regression analysis showed a moderate significant correlation between the weakest VL thickness and sustained gait speed after 3 weeks of routine physical therapy ( r = 0.590, P = 0.044). We also found both strong significant correlations between VL pennation angle of fibers and spasticity ( r = 0.653, P = 0.021), as well as fascicle length and spasticity ( r = 0.647, P = 0.023). A secondary analysis showed that a strong link was found between VL muscle thickness and sustained gait speed when we included the mean thickness value of both muscles in each patient, instead of the weakest muscle alone ( r = 0.606, P = 0.037). Our analysis did not show any significant correlation between ultrasound measurements and muscle peak torque measured on an isokinetic device for VL and BF muscles. We also did not find any significant link between BF ultrasound parameters and clinical parameters. This work suggests that architectural changes in thigh muscles, especially the VL, seem to be linked with a gain in sustained gait speed whereas it might enhance spasticity in MS patients. This result might assess that a bigger muscle thickness could be the consequence of a higher density of slow twitch oxidative type I muscle fibers. This assessment could be confirmed in a higher evidence level study.