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Excessive drooling of saliva or hypersialorrhea is a common problem in neurodegenerative disorders such as motor neuron disease or Parkinson′s disease. It is usually caused by swallowing dysfunction and can facilitate choking, aspiration, and chest infections. Socially it is embarrassing and disabling. There are not many treatment options. Anticholinergic drugs are sometimes tried but are usually of little benefit and side effects (orthostatic hypotension, dizziness, and mental confusion, particularly in the elderly) limit their usefulness.
Occasionally, as a more drastic treatment irradiation of the parotid gland is carried out when hypersialorrhea becomes intractable.
Apart from its established usefulness in dystonia, spasticity and strabismus there are some data showing that botulinum toxin injections are effective in autonomic disorders—for example, gustatory sweating1 and hyperhidrosis of the palm.2 It has been hypothesised that botulinum toxin may help in sialorrhea.3 In a historical note Erbguth recently pointed out the potential use of botulinum toxin for hypersalivation, quoting a paper by the German physician and poet Justinus Kerner written in 1817.4
Botulinum toxin inhibits acetylcholine release in nerve terminals mainly at the neuromuscular junction, but also in sympathetic and parasympathetic ganglion cells and in postganglionic parasympathetic nerves, by blocking SNAP-25, a protein involved in the fusion of acetylcholine containing vesicles with the plasma membrane.5
Against this background we evaluated the usefulness of botulinum toxin injections into the parotid gland in four patients with excessive drooling of saliva, with their consent. One patient had young onset secondary generalised dystonia with severe mouth opening spasms, one had advanced Parkinson′s disease, the third patient had progressive supranuclear palsy, and the fourth patient had motor neuron disease. Drooling in these patients was so severe that they had to wear a bib or carry a towel around their neck. With one exception 20 units of Dysport( (Ipsen) were injected superficially subcutaneously above the angle of the mandible at the posterior margin of the masseter muscle, avoiding the bulk of the muscle. The shorter version (5/8”) of the 25 gauge needle was used. Because worsening of dysphagia was feared only 10 U Dysport were injected into each parotid gland in the patient with motor neuron disease. Drooling did not significantly improve in this patient, possibly due to the low dose of botulinum toxin used. He declined further treatment.
All the other patients had a beneficial response beginning by the end of the first week and lasting 6 weeks in one patient and 3 to 4 months in the others. Apart from subjective improvement reported by the patients and caregivers, reduction of drooling was demonstrated by the fact that the patients did not have to use a bib or towel. One patient had mild worsening of existing dysphagia. Two patients had mild chewing difficulties, possibly due to diffusion of the toxin into the masseter and one patient complained of a dry mouth. None developed facial weakness. All three patients considered the response good enough and side effects sufficiently minimal for them to continue botulinum toxin treatment at regular intervals.
Injections of botulinum toxin into the parotid gland (and other salivary glands) may be an effective and simple treatment for excessive disabling drooling of saliva in selected patients.
AM was supported by the Ernst Jung-Stiftung für Wissenschaft und Forschung in Hamburg, Germany.