Parkinson’s disease is a complex motor disorder that can cause unintentional or uncontrollable movements. It typically occurs due to low levels of dopamine in the brain. Dopamine is a chemical that plays an important role in movement and coordination.
Parkinson’s disease (PD) is a progressive disorder that develops due to the degeneration of nerve cells in the brain that control movement. Normally, dopamine and other neurotransmitters work together to help coordinate movement. But without sufficient dopamine, this is not possible.
In this article, we will discuss the role of dopamine in Parkinson’s disease, as well as symptoms, diagnosis, and treatment options for the condition.
Parkinson’s disease is a neurodegenerative disorder of the nervous system that affects movement and worsens over time.
The condition occurs due to damage or death of nerve cells, or neurons, in an area of the brain called the
Neurons in the substantia nigra are dopaminergic. This means they are responsible for producing dopamine. If they are unable to produce dopamine, a person will likely begin to experience movement-related problems, such as tremors, rigidity, slowness of movement, and poor balance, which are all symptoms of Parkinson’s disease.
Dopamine is the chemical messenger that transmits signals between the substantia nigra and the corpus striatum. Researchers may refer to this as the nigrostriatal pathway. Both the substantia nigra and corpus striatum form part of the
Low levels of dopamine may disrupt the nigrostriatal pathway and cause abnormal nerve firing patterns, which can result in movement problems. Evidence suggests that most people with PD lose 60–80% or more of dopamine-producing cells in the substantia nigra by the time they present symptoms.
The four main symptoms of PD include:
- Tremor: This refers to the shaking a person with PD may experience. It often begins in a hand but can start in a foot or the jaw. It features a characteristic rhythmic back-and-forth motion and is most obvious at rest or when under stress. It may also disappear during sleep.
- Rigidity: This refers to muscle stiffness or difficulty moving. Often, the muscles remain constantly tense, which may cause a person to feel stiff or achy.
- Bradykinesia: This refers to slow or difficult movement, which can make performing simple tasks difficult. This may mean that routine activities such as washing or dressing now take much longer.
- Postural instability: Changes in posture and poor balance can increase the risk of falls and potential injuries.
People may not experience PD the same way, and the progression of the condition may also differ among individuals.
Early symptoms may be subtle and occur gradually. People may experience mild tremors, start noticing difficulty moving, or realize that tasks begin to take longer to complete. Some may notice that symptoms begin on one side of the body but eventually affect both sides. Symptoms are often less severe on one side than the other.
As the condition progresses, symptoms may start to interfere more with daily tasks. People may notice that shaking makes it very difficult for them to eat, they struggle getting out of a seat, and they may speak too softly or with hesitation.
Researchers are still unsure on the precise cause of PD. At present, evidence suggests that it most likely results from a combination of genetics and exposure to environmental factors that trigger the condition.
Scientists have identified that PD occurs when neurons in the brain become impaired or die and start producing less dopamine. However, they are unclear exactly what causes this. The National Institute of Neurological Disorders and Stroke suggests the following potential causes:
- Genetics: Several genetic mutations appear to have links with PD. However, researchers do not consider the condition to be hereditary. Research suggests that genetic factors may only account for roughly 10% of cases.
- Environment: Exposure to certain toxins, such as MPTP or manganese, may result in the development of PD. There may also be many other environmental factors that may contribute to the condition in genetically susceptible individuals.
- Lewy bodies: A person with PD may have deposits of a protein called alpha-synuclein in their brain. Experts may refer to this protein clump as Lewy bodies. The accumulation of these proteins may cause the degeneration of neurons that typically results in PD.
- Mitochondria: Many people may refer to mitochondria as the powerhouses of the cell. Some research indicates that mitochondrial dysfunction may cause the neurodegeneration that results in PD.
Currently, there is no specific test for PD. A doctor may diagnose PD based on:
- a neurological exam and medical history
- blood and other laboratory tests
- brain scans
Some diagnostic tests a doctor may perform include:
- DaTscan: This is an imaging technique that determines how much dopamine is available in a person’s brain. It is a specific type of nuclear medicine called single photon emission computed tomography (SPECT).
- MRI or CT scan: These other scans can rule out a stroke or brain tumor, which may cause similar symptoms.
- Blood tests: A doctor may suggest a blood test to rule out other possible causes, such as liver damage or abnormal thyroid hormone levels.
- Levodopa test:
Levodopa (L-Dopa)is the precursor to dopamine and a drug that can boost dopamine levels. If a person displays improved symptoms after taking L-Dopa, it indicates a diagnosis of PD.
Risk factors for PD may include:
- Age: The incidence of PD increases significantly with age.
- Environment: Exposure to certain pesticides may increase the risk of PD.
- Genetics: People have an increased risk of developing PD if they have a close relative with the condition.
- Sex: PD typically affects more men than women.
Currently there is no cure for PD, however, treatments may help improve symptoms. Treatment options may include:
- Medication: Certain drugs may help to either boost dopamine levels, affect other neurotransmitters such as acetylcholine, or help manage non-motor symptoms such as depression. For example, people often take levodopa and carbidopa tablets to boost dopamine levels in the brain.
- Surgery: Surgery may be an option when drugs are no longer as effective. One surgical option is
deep brain stimulation. This involves placing electrodes in the brain that painlessly stimulate it to help reduce many of the motor symptoms of PD.
- Complimentary and supportive therapies: Many therapies may provide some relief from symptoms of PD. These can include a healthy diet, exercise, tai chi, yoga, and massage therapy.
Parkinson’s disease is a neurodegenerative disorder that affects movement. It occurs due to low levels of dopamine in the area of the brain that facilitates movement. Without sufficient dopamine, the brain is unable to transmit signals to correctly coordinate movement.
Experts are still unsure of the exact cause of Parkinson’s disease, but suspect that genetics and the environment play a role. Current treatment options include drug therapy, surgery, and complementary therapies.