Gastrointestinal motility problems in patients with Parkinson's disease: Epidemiology, pathophysiology and guidelines for management

Gastrointestinal dysfunction is a frequent feature of Parkinson's disease and may be characterised by disordered salivation, dysphagia, gastroparesis, constipation and defecatory dysfunction. Excess saliva is noted by at least 70% of patients with Parkinson's disease and is caused by decreased swallowing frequency rather than overproduction of saliva. Treatment is largely nonpharmacological, although more effective management of dysphagia may also reduce saliva accumulation. Anticholinergic drugs are best avoided. Dysphagia develops in 50% or more of individuals with Parkinson's disease and may be due to oral, pharyngeal or oesophageal factors. Behavioural techniques taught by a speech/swallowing therapist may be useful, but optimum employment of dopaminergic medications may also provide significant improvement in 30 to 40% of patients. Surgical approaches, such as cricopharyngeal myotomy, may be appropriate in selected individuals. Impaired gastric emptying may occur in Parkinson's disease and interfere with levodopa absorption in addition to producing bloating and other symptoms. Prokinetic agents, such as cisapride and domperidone, have been successfully utilised for this problem. Bowel dysfunction in Parkinson's disease has been separated into constipation, due to slowed colon transit, and defecatory dysfunction, due to discoordinated anorectal muscular function, but the two conditions often coexist. Fibre, fluid and prokinetic agents may improve constipation; unproven modalities, such as apomorphine and botulinum toxin injections, may hold the best promise for ameliorating defecatory dysfunction.