Background: Long-term therapy with botulinum toxin is sometimes associated with therapy failure following repeated injections of the neurotoxin, presumably due to specific antibody production. Primary therapy failure with botulinum toxin is less common and poorly understood.
Objectives: To examine the effectiveness of the botulinum neurotoxin Dysport® in patients with blepharospasm and hemifacial spasm after primary or secondary failure with Botox® treatments. .
Methods: In this case series study, eight patients with blepharospasm and hemifacial spasm who experienced primary or secondary therapy failure with Botox were treated with Dysport. In order to render an equivalent Dysport dose, a conversion ratio of 1:3 to 1:4 Botox /Dysport was used.
Results: Two patients, one with blepharospasm and the other with hemifacial spasm, who showed primary therapeutic failure with Botox showed good response to Dysport treatments. One patient with tardive blepharospasm did not respond to either drug. Two patients with blepharospasm and three patients with hemifacial spasm who experienced Botox secondary therapy failure responded well to Dysport treatments.
Conclusions: Botox and Dysport are both serotype A botulinum toxins but carry different characteristics of biological activity. These differences possibly account for the favorable therapeutic response to Dysport in patients with hemifacial spasm or blepharospasm following failure with Botox treatments.