Parkinson’s Disease (PD) belongs to a group of conditions called motor system disorders which result from the loss of dopamine-producing brain cells.
In the brain, dopamine functions as a neurotransmitter – a chemical released by nerve cells to send signals to other nerve cells. Several important diseases of the nervous system are associated with dysfunctions of the dopamine system, including Parkinson’s disease.
Dopamine is available as an intravenous medication that acts on the sympathetic nervous system (activates the “fight or flight” response), but because dopamine cannot cross the blood–brain barrier, dopamine given as a drug does not directly affect the central nervous system. To increase the amount of dopamine in the brains of patients with diseases such as Parkinson’s, L-DOPA (the precursor of dopamine in drug form) is often given because it crosses the blood-brain barrier relatively easily.
The four primary symptoms of PD are:
- Tremor, or trembling in hands, arms, legs, jaw and face
- Rigidity, or stiffness of the limbs and trunk
- Bradykinesia, or slowness of movement
- Postural instability, or impaired balance and coordination
As these symptoms become more pronounced, patients may have difficulty walking, talking or completing other simple tasks. PD usually affects people over the age of 50. Early symptoms of PD are subtle and occur gradually, although in some people the disease may progress relatively quickly. As the disease progresses, the tremor which affects the majority of PD patients may begin to interfere with daily activities. Other symptoms may include depression and emotional changes, difficulty in swallowing, chewing and speaking, urinary problems or constipation, skin problems and sleep disruptions. There are currently no blood or laboratory tests that have been proven to help diagnose PD. Accurate diagnosis is based on medical history and neurological examination and can be difficult.
There is no cure for PD, although developing cell therapies hold promise. PD is both chronic and progressive, meaning its symptoms grow worse over time. While some patients may experience only minor motor disruptions, some people become severely disabled. Tremor is the major symptom for many patients, but the presence of other symptoms may be more troublesome or debilitating. Individual symptoms are unpredictable and the intensity of symptoms vary from person to person.