The effects of electrical stimulation exercise on muscles injected with botulinum toxin type-A (botox)

Abstract

Botulinum toxin type A (BTX-A) is a frequently used treatment modality for a variety of neuromuscular disorders. It acts by preventing acetylcholine release at the motor nerve endings, inducing muscle paralysis. Although considered safe, studies suggest that BTX-A injections create adverse effects on target and non-target muscles. We speculate that these adverse effects are reduced by direct electrical stimulation (ES) exercising of muscles. The aims were to determine the effects of ES exercise on strength, mass, and contractile material in BTX-A injected muscles, and to investigate if BTX-A injections affect non-target muscles. Seventeen New Zealand White (NZW) rabbits were divided into three groups: (1) Control group received saline injections; (2) BTX-A group received monthly BTX-A (3.5U/kg) injections into the quadriceps for six months and (3) BTX-A+ES group received monthly BTX-A injections and ES exercise three times a week for six months. Outcome measures included knee extensor torque, muscle mass, and contractile material percentage area in injected and contralateral, non-injected quadriceps. Glycogen depletion and direct muscle stimulation were used to assess possible muscle inhibition in non-injected quadriceps. ES exercise partially prevented muscle weakness, atrophy, and contractile material loss in injected muscles, and mostly prevented muscle degeneration in contralateral, non-injected muscles. Non-injected muscles of BTX-A+ES group showed higher force with direct muscle compared to nerve stimulation, and retained glycogen following the depletion protocol, suggesting that BTX-A inhibited activation in non-target muscles. We conclude that ES exercise provides some protection from degeneration to target and non-target muscles during BTX-A treatments.