BACKGROUND: There is clinical and experimental evidence that botulinum toxin applied to the healthy side of patients with facial paralysis positively affects functional recovery of the paralyzed side. The authors created an experimental model to study the effects of botulinum toxin injection in the gastrocnemius muscle contralateral to the side of tibial nerve lesion/repair in rats. METHODS: Fifty rats were allocated into five groups: group I, control; group II, tibial nerve section; group III, tibial nerve section and immediate neurorrhaphy; group IV, tibial nerve section, immediate neurorrhaphy, and botulinum toxin injected into the contralateral gastrocnemius muscle; and group V, botulinum toxin injected into the gastrocnemius muscle and no surgery. Assessment tools included a walking track, electromyography, gastrocnemius muscle weight measurement, and histologic analysis of the nerve. RESULTS: Paralysis in group V was transient, with function returning to normal at 8 weeks. At 12 weeks, group V had lower latency levels. At week 12, group IV showed higher functional outcomes and amplitude levels than group III, and lower muscle atrophy on the side injected with botulinum toxin compared with group V. CONCLUSION: Transient paralysis of the contralateral gastrocnemius muscle by botulinum toxin type A improved functional recovery in rats that underwent section and repair of the tibial nerve.
BACKGROUND: There is clinical and experimental evidence that botulinum toxin applied to the healthy side of patients with facial paralysis positively affects functional recovery of the paralyzed side. The authors created an experimental model to study the effects of botulinum toxin injection in the gastrocnemius muscle contralateral to the side of tibial nerve lesion/repair in rats. METHODS: Fifty rats were allocated into five groups: group I, control; group II, tibial nerve section; group III, tibial nerve section and immediate neurorrhaphy; group IV, tibial nerve section, immediate neurorrhaphy, and botulinum toxin injected into the contralateral gastrocnemius muscle; and group V, botulinum toxin injected into the gastrocnemius muscle and no surgery. Assessment tools included a walking track, electromyography, gastrocnemius muscle weight measurement, and histologic analysis of the nerve. RESULTS:Paralysis in group V was transient, with function returning to normal at 8 weeks. At 12 weeks, group V had lower latency levels. At week 12, group IV showed higher functional outcomes and amplitude levels than group III, and lower muscle atrophy on the side injected with botulinum toxin compared with group V. CONCLUSION: Transient paralysis of the contralateral gastrocnemius muscle by botulinum toxin type A improved functional recovery in rats that underwent section and repair of the tibial nerve.