Font Size

Parkinson Disease Dementia (cont.)

Parkinson disease is caused by loss of neurons in a region of the brain that coordinates motor functions (movement).

These cells produce a chemical messenger (neurotransmitter) called dopamine.
Dopamine is involved in the control of motor movement in the brain.
When the level of dopamine in the brain is very low, there is loss of control of movement, one of the main features of PD.

We do not know exactly why dopaminergic neurons die.

A small number of cases of PD are hereditary (run in families), but most are not.
Research into the genetics of PD has identified several gene abnormalities that are linked with some cases of the disease.
For example, a gene known as SNCA (for alpha synuclein) is involved in PD. Some hereditary forms of PD are linked to mutations in this gene.
More recently, scientists have discovered that simply having more than 2 copies of the normal SNCA gene is also linked to PD. The form of the disease linked to this abnormality has an earlier onset than typical PD, progresses more rapidly, and is more likely to lead to dementia.

Some people with PD and dementia have changes in their brain like those in people with Alzheimer disease.

Risk factors for dementia in patients with PD are as follows:

Age 70 years or older
Score greater than 25 on the Parkinson Disease rating scale (PDRS): This is a test that doctors use to check for progress of the disease.
Depression, agitation, disorientation, or psychotic behavior when treated with the PD drug levodopa
Exposure to severe psychological stress
Cardiovascular disease
Low socioeconomic status
Low education level