Clinical symptoms and time course of Parkinson’s disease progression

The development of PD is generally slow and progressive.¹ While diagnosis tends to occur with the onset of motor symptoms, this can be preceded by a long prodromal phase of 15 years or more.³ This prodromal phase is typically characterised by a range of non-motor symptoms, including sleep disorders, depression, and constipation.³ One of the most common symptoms is ‘REM sleep behaviour disorder’, in which affected individuals can become physically, even violently, active during the REM (rapid eye movement) stage of sleep.^1,3

Additional non-motor symptoms develop following clinical diagnosis and, as the disease progresses, cause increasing disability.² Some symptoms, such as postural instability, dysphagia, and dementia, tend to occur in more advanced disease.¹

After several years of levodopa therapy, complications can begin to appear.¹ These may include ‘fluctuations’, when patients alternate between periods of good symptom control and poor symptom control.¹ In fact, the occurrence of motor response complications (fluctuations and dyskinesias) is one of the main limitations of oral levodopa as a dopamine replacement therapy.¹