Effect of botulinum toxin in the treatment of drooling: a controlled clinical trial. Randomized trial of botulinum toxin injections into the salivary glands to reduce drooling in children with neurological disorders.
To investigate the clinical effectiveness of botulinum neurotoxin type A (BoNT) to reduce drooling in children with cerebral palsy (CP).
                A controlled clinical trial was performed in which the results of single-dose BoNT injections in the submandibular glands were compared with treatment with scopolamine. Forty-five children who had CP and experienced severe drooling were enrolled. Drooling severity was measured at baseline, during application of scopolamine, and at different intervals after BoNT injections up to 24 weeks, using the Drooling Quotient (DQ), the Teacher Drooling Scale (TDS), and Visual Analog Scales (VAS).
                Drooling was reduced during scopolamine application as well as after BoNT injections. Compared with baseline, the mean DQ showed a significant decrease throughout the study. Greatest reductions were achieved 2 to 8 weeks after BoNT injection. No significant differences were found between scopolamine measurements and those up to 24 months after BoNT injection. Using VAS, parents recorded the effect on drooling in which significant differences were found between baseline VAS score and all follow-up assessments. According to our definition of "success to therapy," demanding a 2-point decrease on the TDS, 61.5% of patients responded to BoNT injections. Analysis of the DQ demonstrated a response rate of 53% of the patients to scopolamine and 48.7% to BoNT until 24 weeks after BoNT injections, the actual duration of this study. As a reaction to scopolamine, 71.1% of the patients had moderate to severe side effects. Only nonsevere, incidental side effects were reported after BoNT injections.
                During scopolamine application as well as after intraglandular BoNT injections, a clinically relevant reduction in drooling was achieved in children with CP, demonstrating maximum effect 2 to 8 weeks after injections. This is the first controlled clinical trial that confirmed a significant effect of BoNT injections in the treatment of drooling. General anesthesia was needed for all children. BoNT injections show fewer and less serious side effects than transdermal scopolamine treatment. The primary aim of this randomized, controlled trial was to assess the effectiveness of botulinum toxin A (BoNT-A) injections into the submandibular and parotid glands on drooling in children with cerebral palsy (CP) and other neurological disorders. Secondary aims were to ascertain the duration of any such effect and the timing of maximal response. Of the 48 participants (27 males, 21 females; mean age 11y 4mo [SD 3y 3mo], range 6-18y), 31 had a diagnosis of CP and 15 had a primary intellectual disability; 27 children were non-ambulant. Twenty-four children randomized to the treatment group received 25 units of BoNT-A into each parotid and submandibular gland. Those randomized to the control group received no treatment. The degree and impact of drooling was assessed by carers using the Drooling Impact Scale questionnaire at baseline and at monthly intervals up to 6 months postinjection/baseline, and again at 1 year. Maximal response was at 1 month at which time there was a highly significant difference in the mean scores between the groups. This difference remained statistically significant at 6 months. Four children failed to respond to the injections, four had mediocre results, and 16 had good results. While the use of BoNT-A can help to manage drooling in many children with neurological disorders, further research is needed to fully understand the range of responses.
This systematic review found high level evidence supporting the use of BoNT-A as an adjunct to managing the upper limb in children with spastic CP. BoNT-A should not be used in isolation but should be accompanied by planned occupational therapy.
Further research is essential to identify children most likely to respond to BoNT-A injections, monitor longitudinal outcomes, determine timing and effect of repeated injections and the most effective dosage, dilution and volume schedules. The most effective adjunct therapies including frequency and intensity of delivery also requires investigation.