|
Need-to-know anatomy
Parkinson's disease occurs when, for unknown reasons, nerve cells that produce dopamine in the brain die. Dopamine is a "neurotransmitter," which means that it carries messages between cells. The region of the brain affected--the basal ganglia--plays a crucial role in regulating smooth motor function such as body posture, muscle tone, and muscle movements. The basal ganglia and their connections are a group of gray matter nuclei deep within the brain. Examples include the putamen, globus pallidus, subthalamic nucleus, substantia nigra, and caudate nucleus.
In Parkinson's disease, the number of dopamine-producing cells in the substantia nigra declines. The falloff in dopamine makes it difficult for an individual to control muscle movements and leads to symptoms such as slow movements, tremor, and rigidity.
On autopsy, collections of proteins inside the nerve cells, known as Lewy bodies, are seen in the midbrain of people with Parkinson's disease. These are a sign of cell death. How Lewy bodies form and the role they play in the neurodegenerative process are poorly understood, but they are a hallmark of Parkinson's disease. Lewy bodies are also linked with Lewy body dementia, a disorder whose symptoms are similar to those of Parkinson's patients (slow movements, rigidity, tremor, shuffling gait) and also Alzheimer's patients (confusion, loss of memory). Researchers do not yet understand whether Lewy body dementia is a distinct disorder or possibly a variant of Alzheimer's or Parkinson's. Hallucinations early in the course of a patient's decline are another sign supporting the diagnosis of Lewy body dementia.
|
