Parkinson's Disease 101

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Follow along with me: Parkinson’s Disease 101 will be a four-part series!

For the next two months I’ll be writing about Parkinson’s disease in an effort to raise awareness and money for this devastating neurodegenerative disease. I’ll be walking in this year’s Parkinson’s Foundation Moving Day fundraiser. Please support me by clicking the button below to donate!

The Goal

Last year I published a scientific paper that I am incredibly proud of: Genetic analysis and natural history of Parkinson’s disease due to the LRRK2 G2019S variant.¹ What started out as a “bite sized” project for my postdoctoral fellowship turned into a collaborative and amazing learning experience. I learned so much during this process, and I want to impart some of this knowledge onto you! Scientific papers can be so full of jargon and technical terminology, making them a little intimidating to read. Therefore, my goal is to break down this paper into digestible short posts to take away the most important information.

If you are feeling brave, you can read the original article: link here. Otherwise, let’s start with some background on Parkinson’s disease.

Parkinson’s Disease

Parkinson’s disease (PD) is a slowly progressing neurodegenerative condition characterized by the classic motor symptom of shaking or tremor. However, there are many other motor symptoms such as slowness of movement, the arms may swing less while walking, and instability of posture may result in imbalance and falls.

The term “neurodegenerative” refers to cells in the brain that degenerate, or die off, leading to the symptoms we see in PD. There are several different types of cells in the brain, but the main type of cells that are impacted in PD are called neurons. Neurons are the communication cells of the brain, and act like wires that connect different areas of the brain to each other.² Neurons serve a whole host of functions, including everything from vision to the planning of future actions, like your next vacation.

In PD, the neurons in a specific region start to degenerate. This region, called the substantia nigra (Latin for “black substance” due to its dark pigment), is deep in the middle of the brain. The neurons in the substantia nigra produce a molecule called dopamine. Dopamine is a molecule that is sent between neurons that are involved in coordinating muscle movements, often referred to as the motor system.³ Given its role in communication in the brain between neurons, its given the fancy title “neurotransmitter”.

The loss of these dopamine producing and transmitting neurons in the substantia nigra are associated with the motor symptoms we see in PD. But to say that PD is limited to motor symptoms would be seeing just the tip of the iceberg.

When I first started researching PD a few years ago, I was absolutely shocked to discover a whole host of underlying non-motor symptoms. These include, but are not limited to:

• hyposmia - loss of smell

• REM sleep behavior disorder - acting out your dreams while sleeping

• orthostatic hypotension - lightheadedness/ dizziness and fainting upon standing

• constipation

• urinary dysfunction (frequency, urgency)

• cognitive impairment (attention and memory difficulties)

• anxiety/depression

• hallucinations

Often, many of these symptoms can begin to appear years or even decades before motor symptoms of PD. These signs and symptoms that precede the formal development of PD are called “prodromal symptoms”.

But why do those neurons in the substantia nigra degenerate? This, my reader, is the big unanswered question. In short, the answer is a complex interplay between one’s environment, genetics, processes that occur within the cells of the body and brain, lifestyle, and probably many more things that we have yet to understand.

Scientists like myself at try to attack this problem from focused areas, as it is difficult to address all of these angles at once. The scientific paper that serves as the centerpiece of this series examines how two key areas impact symptoms and risk of developing PD:

• genetics

• lifestyle/environment

Great! Now that you have some background on PD and the areas we are focusing on, you are better prepared for the next post that will dive a little deeper on how genetics, lifestyle, and the environment can increase our understanding of Parkinson’s Disease.

Summary

Parkinson’s disease is caused by the degeneration of dopamine producing neurons in the substantia nigra, and is characterized by several motor and non-motor symptoms. Some non-motor symptoms, like loss of smell and acting out your dreams while asleep, can precede a diagnosis of Parkinson’s by many years and even decades. The exact reason why these neurons degenerate is unknown, but researchers use a variety of methods, like genetics and examination of symptoms, to better answer this question.

For the next two months I’ll be writing about Parkinson’s disease in an effort to raise awareness and money for this devastating neurodegenerative disease.
I’ll be walking in this year’s Parkinson’s Foundation Moving Day fundraiser. Please support me by clicking the button below to donate!

1. Kmiecik, M. J., Micheletti, S., Coker, D., Heilbron, K., Shi, J., Stagaman, K., Filshtein Sonmez, T., Fontanillas, P., Shringarpure, S., Wetzel, M., Rowbotham, H. M., Cannon, P., Shelton, J., Hinds, D. A., Tung, J. Y., 23andMe Research Team, Holmes, M. V., Aslibekyan, S., Norcliffe-Kaufmann, L. (2024). Genetic analysis and natural history of Parkinson’s disease due to the LRRK2 G2019S variant. Brain, 147(6), 1996–2008. https://doi.org/10.1093/brain/awae073

2. How many of these wires (i.e., neurons) are there in the brain? Research estimates tens of billions (somewhere between 61–99 billion), but it is difficult to produce a precise estimate (see https://doi.org/10.1093/brain/awae390).

3. Dopamine is also involved in other systems, including the reward system and cognitive functions, such as attention, learning, and memory.