77 Submandibular Duct Ligation After Botulinum Neurotoxin A Treatment of Drooling in Children With Cerebral Palsy 3 production,18 recurrence in the long-term is rather common in surgery such as duct ligation.14 One of the suggested explanations involves upregulation of the sublingual and minor salivary glands to maintain sufficient saliva, thus preventing xerostomia and promoting dental health. Another theory explains recurrence by the development of alternative salivary pathways.15 Therefore, future research should focus on recurrence after bilateral submandibular duct ligation in the longterm. Although not specific to submandibular duct ligation alone, previous studies regarding glandular duct ligation to treat sialorrhea have reported varying success rates from 50% to 81%.15,19–22 Our success rate of 83% after 8 weeks exceeds these previously reported results for both submandibular and combined duct ligations but is in line with former success rates reported at our centre (88.9%). However, this study involved patients who were included in a previous study conducted at our centre.16 Therapeutic success 8 weeks after BoNT-A treatment was 69%, which is slightly higher compared to the 46% to 65% success rates reported in other studies carried out at our centre.4,6,16,23 It must be noted that some authors define therapeutic success by either drooling quotient or VAS or use a combination with a 50% reduction in VAS and/or a 2SD reduction in drooling quotient. Interestingly, our findings suggest that neither BoNT-A treatment success nor treatment failure precludes subsequent treatment response to bilateral submandibular duct ligation. This might be explained by the variable response to BoNT-A treatment across individuals24 or by a difference in the mechanism of action between BoNT-A and bilateral submandibular duct ligation, even though both treatment strategies aim to reduce salivary flow from the submandibular glands. Adverse effects occurred in 10.3% of children after BoNT-A injection, which is lower than the 33% reported adverse effects mentioned in a recent study on submandibular BoNT-A injections.6 There are several explanations for this difference. First, van Hulst et al.6 encouraged caregivers to contact the speech and language therapist for advice if any change in oral-motor function occurred during the first 8 weeks. Second, caregivers were conceivably more attentive to changes
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