A Study to Assess the Safety and Efficacy of Levodopa-carbidopa Intestinal Gel (LCIG) for the Treatment of Non-motor Symptoms in Patients With Advanced Parkinson's Disease

* Subject must have a diagnosis of idiopathic Parkinson's disease (PD) according to the United Kingdom Parkinson's Disease Society (UKPDS) Brain Bank Criteria * Demonstrate persistent motor fluctuations in spite of individually optimized treatment * Subject must experience a minimum of 3 hours "Off" time

* Subject's PD diagnosis is unclear or there is a suspicion that the subject has a Parkinsonian syndrome such as secondary Parkinsonism (e.g., caused by drugs, toxins, infectious agents, vascular disease, trauma, brain neoplasm), Parkinson-plus syndrome (e.g., Multiple System Atrophy, Progressive Supranuclear Palsy, Diffuse Lewy Body Disease, Corticobasilar Degeneration), or other neurodegenerative disease that might mimic the symptoms of PD. * Subject has undergone neurosurgery for the treatment of Parkinson's disease * Subject for whom the placement of a PEG-J tube for LCIG treatment is contraindicated or is considered a high risk for the PEG-J procedure according to the gastroenterology evaluation (e.g., pathological changes of the gastric wall, inability to bring the gastric wall and abdominal wall together, blood coagulation disorders, peritonitis, acute pancreatitis, paralytic ileus).