Clinical Study to Investigate the Efficacy and Safety of Two Dose Levels of NT 201 Versus Placebo in Treating Chronic Troublesome Sialorrhea in Various Neurological Conditions

Inclusion Criteria: * Documented diagnosis of the basic neurological condition associated with sialorrhea (as above, (i), (ii) or (iii); with onset at least 6 months before screening). * Chronic troublesome sialorrhea related to parkinsonism or stroke or traumatic brain injury (for at least 3 months) at screening, defined as the presence of all of the following, at screening and at baseline and for at least the 3 months before screening (where retrospective response to questionnaires is impossible, a statement of equivalent severity will suffice): 1. A Drooling Severity and Frequency Scale \[DSFS\] sum score of at least 6 points and 2. A score of at least 2 points for each item of the DSFS and 3. A score of at least 3 points on the modified Radboud Oral Motor Inventory for Parkinson's Disease \[mROMP\], Section 'III Drooling', Item A). * A score of at most 2 points on the mROMP Section 'II Swallowing Symptoms' Item A) and a score of at most 3 points on Item C), at screening and at baseline. Exclusion Criteria: * Non-neurological secondary causes of sialorrhea. * Unstable concomitant medication influencing sialorrhea (such as anticholinergics for the treatment of parkinsonism; dosages of these medications must have been stable for at least 4 weeks before study entry, i.e. screening, and must be planned to remain stable during the course of the study. * Recent (i.e., four weeks) drug treatment for sialorrhea. * History of recurrent aspiration pneumonia. * Extremely poor dental/oral condition as assessed by a qualified dentist. * Recent (i.e., one year for sialorrhea, 14 weeks for other indications) treatment with - or known hypersensitivity to - Botulinum toxin, or known hypersensitivity to any ingredient of the study preparation. * Recent (i.e., four weeks) changes in anti-parkinsonian medication. * Previous or planned surgery or irradiation to control sialorrhea.