Thursday, August 25, 2011

Parkinson's Disease: Part 1

For this Part 1 on Parkinson's disease, I think it's important that we start with a very simple anatomy lesson, so you can understand where Parkinson's comes from. This is by no means the whole story, but it is the basic understanding one should have about this process.

I think we need to start with a small discussion about the basal ganglia. When you make a thought to move, the reality is that your thought to move is very coarse. It is not the refined, smooth, quick movements that help us drink our coffee, write, catch our-self if we start to stumble, negotiate walking stairs, etc. Our thought to move is more of a thought for a coarse "spurt" of movement in certain area such as the fingers or leg, etc.

That initial thought is then worked over and negotiated by many parts of the brain for the actual smooth, purposeful movements that you wish to have, and need to make throughout your day. One of the large players in negotiating that movement to make it smooth and specific is the basal ganglia.

The basal ganglia sits in the middle of the brain, deep in the brain. The basal ganglia is actually a combination of many on and off switches. These on and off switches help negotiate your movements and help them be fine instead of course and bulky.

Now to talk about how the basal ganglia helps your movements we also need to talk about dopamine. Dopamine is just one of many many types of
neurotransmitters in the human brain. Essentially what you need to know is that a neurotransmitter is just a chemical that helps your brain communicate within itself, amongst its own parts, like someone hired by a company to carry messages back and forth amongst the different departments. Dopamine is used in many parts of the human brain. Essentially your brain found that dopamine was useful and then tried to use it in as many ways as possible to conserve resources. It is actually quite an excellent design that the human brain can use one messenger, dopamine, to say so many different things in different parts of the brain.

But dopamine is one of the main messenger chemicals used in the basal ganglia.

In summary: NOT having enough DOPAMINE, for the BASAL GANGLIA to do its job, is essentially what is going wrong in Parkinson's Disease. That is the cause for the majority of clinical symptoms. That is what we try to address as physicians.

So, you don't have to understand the details of this picture, but I do want you to understand basically:
1: Where the basal ganglia is in the brain compared to other structures
2: That the basal ganglia is made up a few parts that work together

Here is what it looks like from the front. (Look mainly at the silhouette of the human head to the right to see it's basic location in our brain)

And this is what the basal ganglia looks like from the side view:

Now, if you removed it from the brain entirely and held it in your hand, the basal ganglia would look like this. In this picture, many of its parts are labeled.

Now, dopamine has to be made somewhere... and it's made in a factory inside the brain, called the substantia nigra. "Nigra" because when anatomist cut open the brain, the cells that are found in this part of the brain (that make dopamine) look black, and the Latin word for black is nigra. In fact, "substantia nigra" sounds fancy.... but literally means "black substance." In other words, you could say that your dopamine comes from a part of the brain called the black substance.

So, here it is, the substantia nigra. It does look like "black substance." This is where dopamine is made before working in the rest of the basal ganglia to make your movements as purposeful and smooth and fast as you would like them to be.

And here is a quick look at the substantia nigra,
feeding into the basal ganglia to deliver dopamine, to be utilized here.


On to Part 2...