Objective: To quantify the effect of botulinum toxin A injection, by the compound muscle action potential (CMAP) measure from the gastrocnemius muscles (GCM) and to compare them with the clinical data.
Methods: Seventeen legs of 10 cerebral palsy (CP) children were studied with botulinum toxin A injection on the motor points of their GCM. Each GCM was injected up to 6 units of the botulium toxin A per kilogram of the body weight. The CMAP were measured at the motor points of GCM with the surface electrodes on the post-injection day 1, day 3, day 7, 2 weeks and at 1 month then monthly thereafter for 6 months. Physician rating scale (PRS) and the angle of passive ankle dorsiflexion were evaluated at the same time.
Results: The amplitude and the area of the CMAP decreased from post-injection day 1 to 3 months. The most pronounced decrement was seen at 2 weeks post-injection (p＜0.05). The most pronounced increase of the dorsiflexion angle and PRS were seen at 1 and 2 months post-injection, respectively (p＜0.05).
Conclusion: The compound muscle action potential measure can be used for the neurophysiological quantification of the effect of botulinum toxin A, especially for the superficial muscles of extremities.
