Memory Loss & the Brain

Parkinson's disease is a progressive neurological disease involving deterioration of neurons in a region of the brain called the substantia nigra. It affects approximately a million Americans, most of them over the age of 60, although sometimes the disease can appear in people as young as 35 or 40. The causes of Parkinson's disease are unknown. It is named after James Parkinson (1755-1824), an English neurologist who studied the disease.

Parkinson's disease is characterized by motor symptoms, including tremor in muscles that are at rest, rigidity, slowness of movement, difficulty initiating movement, and problems maintaining posture. The onset of these symptoms is usually gradual, and patients may go for a long time without appreciable worsening. Symptoms are usually intermittent in the early stages of the disease, but may become continual late in the course of the disease. In late stages of Parkinson's disease, the face becomes expressionless, eye blinking is infrequent, speech is slow, and the patient may find it difficult to stand upright without falling.

In addition to the motor symptoms in Parkinson's disease, there are also cognitive symptoms which may be evident even in the early stages of the disease. These may include deficits in executive function (especially planning and attention), set-shifting (ability to alternate between two or more tasks), and memory. Approximately 25%-30% of Parkinson's patients develop dementia. It is not yet known whether dementia is actually a symptom of Parkinson's disease or whether patients with Parkinson's disease are for some reason also at higher risk for dementia. A large number of Parkinson's patients also experience psychiatric disorders such as depression, anxiety, or sleep disorders.

Because Parkinson's disease damages neurons in the substantia nigra which produce dopamine, treatment usually involves drugs which work to counteract this shortage of dopamine. For example, levodopa (L-dopa, for short) may be used to help boost brain production of dopamine; L-dopa is a component of the widely-used Parkinson's drug Sinemet. Other medications such as selegiline (also known as deprenyl or Eldepryl) work to increase the efficacy of existing dopamine in the brain. Parkinson's patients may benefit from treatment with several kinds of drugs simultaneously. These drugs can often combat the motor symptoms for a long time, but as the disease progresses and the substantia nigra continues to degrade, the drugs eventually become less effective.

Some patients whose motor symptoms cannot be controlled by medication undergo brain surgery to destroy portions of the brain regions responsible for some of the motor symptoms in Parkinson's disease, or benefit from deep brain stimulation (DBS) -- using thin wires to stimulate electrical activity in the brain. There has also been controversial research involving implantation of cells from aborted fetuses into the brains of Parkinson's patients in an attempt to regrow neurons in the substantia nigra; more recently, scientists are exploring the possibility of using stem cells isolated from healthy adults or grown in the laboratory. As yet, this work is still highly experimental.