What is Parkinson's Disease (PD)?
Parkinson’s disease is a neurodegenerative brain disorder that progresses slowly in most people. What this means is that individuals with PD will be living with PD for 20 years or more from the time of diagnosis. However, having PD does not mean you cannot have a good quality of life. Because there is no cure, your doctors will be focused on finding treatments that help control the symptoms of PD and enable you to manage the disease.
Normally, there are brain cells (neurons) that produce dopamine. These neurons concentrate in a particular area of the brain called the substantia nigra. Dopamine is a chemical that relays messages between the substantia nigra and other parts of the brain to control movements of the human body. Dopamine helps humans to have smooth coordinated muscle movements. When approximately 60 to 80% of the dopamine-producing cells are damaged and stop producing enough dopamine, the motor symptoms of Parkinson’s disease appear. This process of impairment of brain cells is called neurodegeneration.
The current theory (so-called Braak’s hypothesis) is that the earliest signs of Parkinson’s are found in the enteric nervous system, the medulla and in particular, the olfactory bulb, which controls your sense of smell. Under this theory, Parkinson’s only progresses to the substantia nigra and cortex over the years. This theory is increasingly borne out by evidence that non-motor symptoms, such as a loss of sense of smell, sleep disorders, and constipation may precede the motor features of the disease by several years. For this reason, researchers are increasingly focused on these “non-motor” symptoms to both detect PD as early as possible and to look for ways to stop its progression.