Sialorrhea (drooling) is excessive salivation, possibly due to excess flow of saliva but more likely secondary to a reduced frequency of swallowing (e.g., in parkinsonian syndromes) or difficulty swallowing (e.g., motor neurone disease, developmental perisylvian syndrome).
Metallic poisonings (mercury, bismuth, lead) may also produce marked salivation (ptyalism).
If troublesome, treatment of sialorrhea with anticholinergic agents may be tried (atropine, hyoscine), although they may cause confusion in Parkinson’s disease. In extreme cases, irradiation of the salivary glands has been used. Recently, the use of intraparotid injections of botulinum toxin has been found useful.
Bhatia KP, Münchau A, Brown P. Botulinum toxin is a useful treatment in excessive drooling of saliva. Journal of Neurology,Neurosurgery and Psychiatry 1999; 67: 697