A randomised double-blind placebo-controlled trial has shown radiation of parotid or submandibular glands to be successful in the treatment of drooling in Parkinsonian patients.
Drooling occurs in 32 – 74% of patients with Parkinsonism. It is mainly caused by impaired swallowing of saliva. This can cause significant physical and emotional distress, and sometimes patients avoid social activities and interactions because of it.
Whilst there are other treatment approaches including oral anticholinergics, injection of botulin toxin and oral motor training, these may cause negative side effects and can be difficult to administer. There is therefore a need for an easy and effective treatment.
Earlier radiation therapy studies showed the potential to reduce drooling. This tends to be associated with only mild side effects such as dry mouth, thick saliva, taste changes, skin reaction and pain. However, previous studies did not differentiate between radiation of parotid and submandibular glands. Therefore, the trial by Steenbakkers et al, specifically assessed the efficacy and safety of submandibular and parotid salivary gland irradiation to reduce drooling.
The trial method
A prospective, randomised, double-blind, placebo-controlled trial of radiotherapy vs sham radiotherapy was conducted at the University Medical Center Groningen, the Netherlands in 31 patients with Parkinsonism and severe drooling.
Radiotherapy was given as 2 fractions (doses) of 6 Gy with a one week interval between the fractions. The patients were divided into three groups: Parotid gland radiation (n=11), Submandibular gland radiation (n=10), Sham radiation (n=10). After 6 months, the sham-radiated patients were actively treated after a second randomisation. The primary outcome measure was drooling severity.
Radiotherapy to either the parotid or submandibular glands significantly improved drooling, compared with sham radiation. Parotid- and submandibular radiation was equally effective, but more patients in the submandibular group reported sticky saliva vs. patients treated by parotid radiation (33% vs. 13%).
The trial found that salivary gland radiotherapy significantly improves drooling in Parkinsonian patients, when compared to the placebo group. Parotid gland radiation had fewer side effects when compared to submandibular gland radiation, and is therefore the preferred mode in this population of 31 patients.
These positive findings are welcomed by the International Organisation for Radiotherapy for Benign Conditions — we particularly acknowledge the effort and dedication by Dr Steenbakkers and his team in order to develop, recruit and report a randomised controlled trial for benign radiotherapy.
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R.J.H.M. Steenbakkers, S.P. van Doornik, A. Vissink, W. Kerdijk, T. van Laar d