The purpose of the study was to determine the effects of Parkinson’s disease (PD) on muscle quality, as measured by echo intensity (MQEI) and specific force (MQSF). We also analyzed correlations and explored MQEI and MQSF across Hoehn and Yahr (H&Y) stage and by medication status. Thirty PD (70.1±8.6 y; H&Y stages 1-4) and 24 CON (71.6±8.6 y) subjects participated in this study. A subgroup of eleven PD participants tested both on and off medication. Clinical assessments included H&Y stage, disease severity, and rigidity; performance measures included mobility and isokinetic ankle strength and power. Echo intensity and muscle thickness measurements were made for the tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL) using ultrasound brightness-mode images. MQSF was calculated as strength/muscle thickness for dorsiflexion (DF) and plantar flexion (PF). No significant differences were found between PD and CON (p > .05). TA MQEI was significantly associated with strength and power; and MG and LG MQEI were differentially correlated with mobility, strength, and power. DF MQSF correlated to all clinical measures and mobility; showed declines across H&Y stage; and was higher on than off medication at fast isokinetic speeds. PF MQSF was associated with rigidity and mobility, and was greater on than off medication at slow speed. Overall, we found muscle quality to be preserved in our PD participants, most likely due to their high levels of physical activity. MQEI and MQSF are beneficial tools in the evaluation of disease progression and function in persons with PD.

Authors: Kylie J. Courtney, Keri L. Strand, Kevin A. Jacobs, Moataz Eltoukhy, Corneliu C. Luca, Joseph F. Signorile