Evaluation of abnormal synergy patterns poststroke: relationship of the Fugl-Meyer Assessment to hemiparetic locomotion

Abstract

Background: Assessment of poststroke motor impairment has historically focused on the ability to move within and outside of abnormal synergistic motor patterns and is typically quantified by the Fugl-Meyer Assessment (FMA). However, it is unclear if the voluntary, isolated movement tasks of the FMA are appropriate for evaluating walking task-specific motor control requirements because walking is cyclical and involves considerable sensorimotor integration.

Objective: The purpose of this study is to test whether the motor impairment measured by the FMA is indicative of motor dysfunction during walking in poststroke adults.

Methods: Thirty-four individuals with chronic poststroke hemiparesis and 17 healthy controls walked for 60 seconds on an instrumented treadmill while recording electromyographic activity (EMG) from 8 lower extremity muscles. EMG recordings were also obtained during the FMA for those with hemiparesis to examine muscle activation patterns. Each participant was examined with a battery of walking-specific clinical and biomechanical assessment tools and stratified based on the FMA synergy (FMS) score. To further quantify muscle activation patterns during walking, a nonnegative matrix factorization (NNMF) determined the number of independent modules required to describe 90% of the total variance in the EMG patterns.

Results: Stratification poorly differentiated motor activation across FMA tasks as well as EMG patterns during walking. While FMS correlated with 2 of 6 walking assessments, the number of EMG modules significantly correlated with all 6 walking performance measures.

Conclusions: Voluntary, discrete activities as performed in the FMA may be inadequate to capture the complex motor behavior in walking. Conversely, walking-specific evaluations such as NNMF appear more appropriate.

Figure 1

Phase descriptions for the gait cycle for someone with right hemiparesis. The first double-support phase defines phase 1; phases 2 and 3 are the first and second 50% of the single-limb support; the second double-limb support (paretic preswing) is defined as phase 4; phases 5 and 6 are the first and second 50% of the swing phase.

Figure 2

Tibialis anterior (TA) bursting patterns during right isolated dorsiflexion (DF;A) and during walking (B). Axes are identical for the 2 tracings. Note the higher amplitude and clear bursting pattern in walking (B) compared with the fairly tonic activity in isolated movements (A); in addition, note the lack of DF movement in (A) compared with functional right DF during the walking cycle in (B).

Figure 3

Walking electromyographic patterns with Fugl-Meyer assessment synergy (FMS) severity. Significant differences between FMS groups are only noted for rectus femoris for phases 2 and 4, demonstrating that those in differing FMS generally activate similarly during walking; differences from controls (black line) can be clearly noticed in tibialis anterior (TA), soleus, gastrocnemius (GASTROC), and gluteus medius (GLUT MEDIUS). * Denotes significant differences in the post hoc analysis.