The causes of dystonia are not fully understood and although currently available treatments can provide effective
symptomatic relief, they cannot provide curative disease modification. Botulinum neurotoxin type A injections are well established for the symptomatic treatment of focal dystonias and post-stroke spasticity. Three proprietary injectable formulations of botulinum neurotoxin type A are currently available: Botox® (onabotulinumtoxinA), Dysport® (abobotulinumtoxinA), and Xeomin® (incobotulinumtoxinA). Of these, only Xeomin® is purified to remove associated complexing proteins, and the resultant reduced protein load may confer reduced immunogenicity. Product labelling currently restricts conventional botulinum toxin type A treatments to a minimum injection interval of 12 weeks; however,feedback from published patient surveys shows a substantial proportion of patients experience re-emergence of symptoms in the weeks prior to reinjection. This review examines clinical studies conducted with Xeomin® (incobotulinumtoxinA) that have featured more flexible injection intervals based on individual patient needs. The available evidence suggests that for selected patients, a more flexible and tailored treatment approach with injection intervals of ≥6 and up to 20 weeks may help optimize symptom relief. In studies where flexibility in injection interval timing was permissible, interval
preferences were varied. Although shorter injection intervals (<12 weeks) with incobotulinumtoxinA were requested and administered to almost half of patients in a pooled analysis of two studies in patients with blepharospasm and cervical dystonia, approximately 25-30% of these patients requested considerably longer injection intervals of between 14-20 weeks. In these studies, effective symptomatic relief was demonstrated and no increases in side effect liability, or increased production of neutralizing antibodies that can lead to treatment failure were observed with <12-week injection intervals compared with ≥12-week injection intervals..