NERVE INJECTION INJURY WITH BOTULINUM TOXIN

The therapeutic use of botulinum toxin (Botox) is increasing in popula rity. Previous studies have shown that various drugs, especially when injected intrafascicularly, can cause major nerve damage. This study e valuates the potential for neurotoxicity of botulinum toxin in a rat s ciatic nerve model. Lewis rats were randomly assigned to one of six gr oups (n = 10/group). Group 1, 2, and 3 rats received, respectively, an intrafascicular, extrafascicular, and extraneural injection of 50 mu l of botulinum toxin (50 UI/ml). Group 4, 5, and 6 rats received 50 mu l of 10% phenol as a positive control. Five animals received saline a s a negative control. Animals were sacrificed at 2 and 7 weeks. Nerves were harvested and processed for histology and morphometry. Nerves in all botulinum toxin groups retained a normal architecture without cel lular infiltration or demyelination. The number and diameter of fibers , the thickness of myelin, and the percentage of neural tissue were co mparable with normal controls. Nerves injected intraneurally with phen ol presented with severe damage, demyelination, and inflammation at 2 weeks and showed signs of early regeneration at 7 weeks. This study de monstrates that in a rat model, even direct intraneural injection of b otulinum toxin caused no damage. This information should encourage the reconstructive surgeon to consider broader applications of this drug.