Botulinum Toxin Reduces Excessive Drooling, Improves Oral Motor Function in Rett Syndrome Patients, Study Says

Botulinum toxin treatment for excessive salivation — known as hypersalivation or sialorrhea — in Rett syndrome can effectively reduce saliva production and may also improve oral motor function, a study reports.

The study, “The Treatment of Hypersalivation in Rett Syndrome with Botulinum Toxin: Efficacy and Clinical Implications,” was published in Neurology and Therapy.

Hypersalivation, a likely secondary effect from impaired oral motor function, can have a negative impact on the quality of life in children with Rett syndrome. Certain factors, such as respiratory problems and treatment with anti-epileptics, can affect excessive drooling.

Injecting botulinum toxin into the salivary glands has been reported safe and effective in reducing saliva production both in adults with neurodegenerative disorders and in children with cerebral palsy. Rett syndrome patients share several clinical features with these children.

For this reason, researchers at the University of Naples Federico II tested whether botulinum toxin treatment of hypersalivation could also be safe and effective for Rett syndrome patients.

The researchers recruited five female Rett syndrome patients, from 13 to 23 years old, with MECP2 gene deletions — the genetic hallmark of the disease — and hypersalivation.  None of them had ever been treated with botulinum toxin prior to their participation in the trial.

All five participants were in wheelchairs and unable to speak. Four patients were receiving enteral nutrition — via a feeding tube — along with nutritional supplements, and three of them were being treated with anti-epileptics.

Using ultrasound guidance, the patients were injected with a fixed dose of botulinum toxin — 150 U of Xeomin (incobotulinumtoxin A)  — in the submandibular and parotid glands (two types of salivary glands) on both sides of the mouth.

The researchers assessed hypersalivation by severity and frequency, using a five-point scale called the Thomas-Stonell and Greenberg Scale (TSGS). The impact of hypersalivation on eating habits, difficulty breathing (dyspnea), and teeth clenching (bruxism) were also evaluated using the four-point Rett Assessment Rating Scale (RARS). The patients were tested on both TSGS and RARS scales prior to botulinum toxin injection, as well as one month and four months after injection.

They found that botulinum toxin injection into salivary glands could decrease saliva production as soon as one month after administration, as assessed by the TSGS, an effect that continued for four months.

They also found that this saliva reduction was linked to better oral motor function in two of the three behaviors examined by RARS. They also observed that eating habits and teeth clenching improved in the month following botulinum toxin injection. However, these benefits went away when the injection’s effects began to wear off. There was also a slight improvement in breathing difficulties.

“We could speculate that an excessive amount of saliva may enhance jaw-closing movements; therefore, a decrease in salivation may improve bruxism,” the researchers wrote. “Unfortunately, our study did not show a correlation between drooling production and respiratory performances, although we found a slight tendency of dyspnoea improvement after [botulinum toxin] treatment.”

Although these results are promising, further studies are needed to test the safety and efficacy of botulinum toxin injection in a larger sample of Rett syndrome patients before it can become widely accepted. In addition, the present study was restricted to one treatment with incobotulinumtoxin A, so researchers will want to know how several injections affect hypersalivation and associated symptoms in Rett syndrome patients.

“This study is limited by the small number of patients, but our results would suggest that [botulinum toxin] injection in salivary glands is safe and effective in reducing saliva production in [Rett syndrome],” the authors wrote.

“Moreover, patients would also benefit from the treatment for more oral motor problems possibly related to hypersalivation like eating difficulties and bruxism. More extensive studies are needed to confirm these data. … [Botulinum toxin] treatment for sialorrhea in patients with Rett syndrome should be encouraged because it is effective and safe, and it may also improve important oral motor functions,” they concluded.