33 Repeated onabotulinum neurotoxin A injections for drooling in children with neurodisability 1 improved drooling in our children during the entire treatment course (Fig. 1). In case of lack of response after repeated injections, combined injections (submandibular and parotid) could be considered. For children aged above 10 years or with low expectation to ‘outgrow’ drooling, we consider surgery. Unlike the objective effect, the subjective effect of the third injection decreased as well. We interpret that the lack of objective effect could be due to the small sample size, parental expectations, or the burden on carers which might have outweighed the benefit of the procedure. Patients may have forgotten the severity of drooling before treatment, and, as such, have a high VAS score once the drooling has resurfaced again. Studies which evaluated the effect of repeated botulinum neurotoxin A in children are scarce.22 One prospective study evaluated the effect of repeated botulinum neurotoxin A andB in parotid and submandibular glands for drooling in childrenwith neurodegenerative disorders. Five out of 30 children showed no effect (decrease in Teacher Drooling Scale) on repeated injections, but it was not mentioned at which injection, so we cannot draw definitive conclusions from this article.22 Another study identified a significant decrease in effect after repeated botulinum neurotoxin B injections for the treatment of drooling, but only after the fifth injection. This study, however, only included a small population of 17 children.23 Furthermore, studies on the effect of repeated botulinum neurotoxin A injections for other indications (e.g. spasticity, epiphora, and axillary hyperhidrosis) also showed a consistent effect.24–27 One prospective observational study found a diminished effect after two to three injections in lower extremity spasticity in children with cerebral palsy.28 Nonetheless, botulinum neurotoxin A was given for other indications and this finding is therefore not fully applicable to our aim. Still, it does show the decrease of effect after repeated use of botulinum neurotoxin A in children. This study also found a treatment success of 74%, defined as ≥50% reduction in drooling quotient and/or VAS at 8 weeks compared to baseline, in this population
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