Time Course Analysis of the Effects of Botulinum Toxin Type A on Elbow Spasticity Based on Biomechanic and Electromyographic Parameters

A schematic setup of biomechanic and electromyographic measurements for quantifying the time course changes of spasticity before and after injections of BTX-A. (A) Portable muscle tone measurement device. The elbow was stretched manually via the wrist cuffs at 4 frequencies. The biomechanic data and electromyographic data were sensed using a portable device (a differential pressure sensor and a lightweight gyroscope) and 2 surface electromyography electrodes, respectively. (B) Biomechanic data. Examples of biomechanic data of reactive resistance and displacement during stretching at 3/2Hz. The dashed lines show the phase lag between resistance and displacement. (C) Electromyographic (EMG) data. Clear reflex electromyographic activities are found in the biceps brachii compared with the triceps brachii during stretching at 3/2Hz.

The processing of biomechanic data. (A) A curve of the reactive torque versus displacement for a single trial of stretches. Phase lag ω was estimated to derive the viscous component. (B) A plot of the reactive torque, T(t) and displacement (shifted by θ). (C) A graphical representation of our analytic approach for deriving the viscous component from the phase lag and averaged complex modulus (ACM). Based on a second-order model, Bω is proportional to the phase lag θ. ACM can be estimated from the curve of T(t) versus X(t+θ) in panel B. (D) Viscous components (Bω_1/3, Bω_1/2, Bω₁, Bω_3/2) estimated from the 4 stretching frequencies were pooled to derive the velocity-dependent viscosity (B).

The processing of electromyographic signals to determine the RET of the stretch reflex. (A) One stretch range is indicated with 2 solid lines (lines A, B) in the curve of joint displacement. The linear-envelope formation of the electromyographic raw signal is shown in panels B, C, and D. The vertical dotted line C marks the first time point where the electromyographic linear envelope exceeds 3 standard deviations from the baseline electromyographic activity, as recorded for 100ms before eliciting the stretch (solid line A). The threshold was then calculated as a percentage of the stretch range (RET = 65.3% in panel A).

Two typical examples of time course data based on the clinical scale (MAS), velocity-dependent property (V-D property) B, and length-related property (L-R property) RET. Compared with the clinical scale, our quantitative parameters B and RET successfully reflect the change in spasticity after the BTX-A injection in subject S6 (panels A, C, E) and subject S2 (panels B, D, F).