What Causes Parkinson's Disease? How does it work?

We really don’t know. It’s super frustrating, I know. So let's focus on what we DO know: how the disease works and what causes the symptoms.

Remember most symptoms are movement related- shaking (tremors), stiffness (rigidity), poor balance and a general slowness of all movement. These symptoms gradually progress as the disease does. There are other non-motor symptoms that affect a person’s mood, sleep cycle and even use of the 5 senses. The thinking process can also be affected and may sometimes result in dementia.

Now on to how the disease works. It all stems from a reduction in the amount of the neurotransmitter dopamine. Dopamine is a brain chemical that is essential for many things, among them… you guessed it, movement. In PD, a decrease in dopamine causes the movement related difficulties. The neurons that release dopamine hang out the in basal ganglia of the brain (it’s deep in the middle- check out this picture for help!)

The Basal Ganglia

A collection of small structures make up the basal ganglia but the one we care about the most is the substantia nigra. You can spot the substanta nigra because it is darker in color than the rest of brain tissue. This is because the cells there are pigmented. In a normally functioning brain the substantia nigra receives information from the rest of the body via the cerebral cortex. It processes that information and sends it back out to the cerbreal cortex (especially the motor cortex for our purposes). Once it sends the signal out, it influences the actions carried out by neurons in the motor cortex. Dopamine that is required for this signaling to be successful so as you can imagine, this is where problems arise. In Parkinson’s Disease, the cells of the substantia nigra die and they can no longer produce dopamine. This decrease produces the symptoms that contribute to a diagnosis of PD.

It’s super complicated, right? But wait, there’s more. The cells of the substantia nigra don’t just die and disappear. They actually stay in the brain and end up with these abnormal structures made of protein inside. These structures are called lewy bodies. The protein clumps together inside the neuron and this, as you can imagine, causes many problems.

Lewy bodies exist outside the substantia nigra, too. They can clump inside cells all over the brain and cause even more widespread damage. A lot of cognitive problems come along with this and the problem even has it’s own name. Lewy Body Dementia.  

Parkinson’s disease itself is not fatal. People with PD may be susceptible to other conditions that lead to premature death. Among the most common, dementia and pneumonia. It is important to remember that with proper symptom management and precautions, people with PD can live long and productive lives. The best way to help is to educate yourself and those around you!

Check out this video for a visual summary of the pathophysiology of PD!

For you information:

Easier reads:

http://www-uptodate-com.offcampus.lib.washington.edu/contents/parkinson-disease-the-basics?source=see_link

http://www-uptodate-com.offcampus.lib.washington.edu/contents/parkinson-disease-symptoms-and-diagnosis-beyond-the-basics?source=see_link

Super complex and in-depth:

http://www-uptodate-com.offcampus.lib.washington.edu/contents/etiology-and-pathogenesis-of-parkinson-disease?source=search_result&search=parkinson%27s+disease&selectedTitle=4~150

References:

Bergman, H. Deuschl, G.(2002). Pathophysiology of Parkinson's Disease: from clinical neurology to basic neuroscience and back. Movement Disorders. Vol 17 (3). 

Retrieved from

http://onlinelibrary.wiley.com.offcampus.lib.washington.edu/store/10.1002/mds.10140/asset/10140_ftp.pdf?v=1&t=i54h1xns&s=0431b8dfd982d82cfa7f4cc0cc5b7e780c584f24

Jankovic, J. (2014). Etiology and pathogenesis of Parkinson disease. UptoDate.

Retreived on from

http://www-uptodate-com.offcampus.lib.washington.edu/contents/etiology-and-pathogenesis-of-parkinson-disease?source=search_result&search=parkinson%27s+disease&selectedTitle=4~150