When the going gets tough: how to select patients with Parkinson's disease for advanced therapies.

Levodopa-induced motor complications of Parkinson's disease, including motor fluctuations and dyskinesias, become increasingly frequent as the disease progresses, and are often disabling. Oral and transdermal therapies have limited efficacy in controlling these problems. Advanced device-aided therapies, including continuous infusion of apomorphine, deep brain stimulation and levodopa-carbidopa intestinal gel can all ameliorate these complications. This review summarises the principles of each of these therapies, their modes of action, efficacy and adverse effects, and gives advice on timely identification of suitable patients and how to decide on the most appropriate therapy for a given patient.