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Clinical Trial
, 13, 25

Quantitative Evaluation for Spasticity of Calf Muscle After Botulinum Toxin Injection in Patients With Cerebral Palsy: A Pilot Study

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Clinical Trial

Quantitative Evaluation for Spasticity of Calf Muscle After Botulinum Toxin Injection in Patients With Cerebral Palsy: A Pilot Study

Yu-Ching Lin et al. J Neuroeng Rehabil.

Abstract

Background: Cerebral palsy (CP) is the most common pediatric disease to cause motor disability. Two common symptoms in CP are spasticity and contracture. If this occurred in the ankle plantar flexors of children with CP, it will impair their gait and active daily living profoundly. Most children with CP receive botulinum toxin type A (BoNT-A) injection to reduce muscle tone, but a knowledge gap exists in the understanding of changes of neural and non-neural components of spasticity after injection. The purpose of this study was to determine if our device for quantitative modified Tardieu approach (QMTA) is a valid method to assess spasticity of calf muscles after botulinum toxin injection.

Methods: In this study, we intended to develop a device for quantitative measurement of spasticity in calf muscles based on the modified Tardieu scale (MTS) and techniques of biomedical engineering. Our QMTA measures the angular displacement and resistance of stretched joint with a device that is light, portable and can be operated similar to conventional approaches for MTS. The static (R2), dynamic (R1) and R2-R1 angles derived from the reactive signals collected by the miniature sensors are used to represent the non-neural and neural components of stretched spastic muscles. Four children with CP were recruited to assess the change in spasticity in their gastrocnemius muscles before and 4 weeks after BoNT-A injection.

Results: A simulated ankle model validated the performance of our device in measuring joint displacement and estimating the angle of catch. Data from our participants with CP showed that R2 and R2-R1 improved significantly after BoNT-A administration. It indicates both neural and non-neural components of the spastic gastrocnemius muscles improved at four weeks after BoNT-A injection in children with CP.

Conclusion: Our device for QMTA can objectively measure the changes in spasticity of the gastrocnemius muscle in children with cerebral palsy after BoNT-A injection.

Keywords: Botulinum toxin; Cerebral palsy; Modified Tardieu scale; Quantitative measurement; Spasticity.

Figures

Fig. 1
Fig. 1
Rationales of spasticity measurement for modified Tardieu scale (MTS) and our quantitative modified Tardieu approach (QMTA). a Conventional MTS approach. b Our QMTA approach. c Expected curves of resistance during a manual stretch. d Expected curves of displacement during slow or fast stretches. Both curves of (c) and (d) are derived from a fast stretch on a spastic ankle joint of a patient with cerebral palsy
Fig. 2
Fig. 2
The spasticity measurement system for the quantitative modified Tardieu approach. a Mechanical parts of the sensing device. The upper and lower parts were connected via four sliding tracks to decrease the friction during compression. b A gyroscope was used to record angular velocity and was applied during ankle displacement to identify the angular displacement. A miniature load cell (load button) was used to record resistance during stretch. c The hand-held sensing device recorded and sent signals (angular velocity and resistance) to a computer via an A/D converter during ankle stretch
Fig. 3
Fig. 3
The simulated foot model for validation tests of our measurement system. a & b The simulated model was designed to rotate around the bearing seat. c & d The movable range was set and calibrated as 0° to 70°, in a range similar to the real foot available range. The resting position (about 40° elevation from the platform) is defined as 0° of the model. e We attached a commercial gyro along with our device to record the angular velocity simultaneously. f Test of the feasibility of R1 and R2 estimation by the displacement and resistance signals of QMTA device
Fig. 4
Fig. 4
Gyro performance of displacement measurement between our device and commercial product (comm. gyro). a Angular velocity signals (with 15Hz low-pass filtering) during four slow and four fast stretches. The signals were almost identical with very good correlation (CC = 0.9957). b The derived displacement signals both showed a drift phenomenon (an upward trend was noted). The green arrows indicated the start position of each stretch and were used as a reference to calculate each stretch displacement. c For all stretch cycles, the displacement from our gyro was very close to the commercial gyro with a maximal error percentage of 1.7 %
Fig. 5
Fig. 5
Displacement and resistance curves of foot model testing with five slow and fast stretches. The green dashed lines indicate the peak of resistance curve and were used to find the parameters of R1 and R2. Displacement of joint model for slow and fast stretches are shown in (a) and (c) respectively. Corresponding resistance curves for slow and fast stretches are shown in (b) and (d) respectively

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