What is Deep Brain Stimulation for Parkinson’s disease?

DBS is electrical stimulation of the brain by using a small machine. DBS can stimulate many brain areas.

DBS is actually approved for many diseases. It is not just a “Parkinson’s surgery”. It can be used for epilepsy and other movement disorders as well.

The basic setup is the same.

The DBS battery is inserted below the chest skin. Two small wires from the battery go up to the head. The wires go through the skull. They are inserted into the desired area of the brain.

For Parkinson’s disease: This target area of the brain is usually the “Subthalamic Nucleus (STN).

In some patients, another area is chosen as the target. This other area is the Globus Pallidus interna (GPi).

How is the target chosen? Read this article [Click here]

DBS can dramatically improve Parkinson’s symptoms. There are many before-after videos available on the internet.

For example, here is a video posted on youtube by the Neuromedical Center in USA.

How does Deep Brain Stimulation (DBS) work?

No one completely understands how Deep Brain Stimulation (DBS) works.

Doctors used to cut small parts of the brain to reduce Parkinson’s symptoms. This surgery is called a “tomy”, meaning “to cut”. For example, Thalamo-tomy, Pallido-tomy.

A small electrical current is used to stop small bleeds during surgery. This is called “electrical cautery”.

While doing this current, they noticed something odd. When they passed a current into certain brain parts, the Parkinson’s tremor disappeared!

Would it be possible to continue the stimulation indefinitely? This question led to the design of the DBS electrical system around 2000. DBS was approved for widespread use in 2002.

Reference:

1. “History & Future of Deep Brain Stimulation” Schwalb 2008: Fascinating article on how Deep Brain Stimulation for Parkinson’s was discovered (lots of pictures, free to read)

Ah Yes!

So, it is one of those things where we don’t know how it works. But years of experience have shown us that it does. Like, complimenting your spouse…

Many researchers believe DBS stimulates the target. Some believe DBS actually causes the target to stop working.

The reality is complex, and as yet, out of reach.

Each of these targets (for example the STN) contain many millions of little cells arranged in very intricate circuits.

Probably, the DBS current stimulates some of these cells, while other cells stop working. Some circuits go into overdrive, while others shut down.

This varying effect also varies according to the current characteristics, especially frequency.

The net effect is, at present, impossible to calculate mathematically.

Empirically though (with our own eyes), we see that when the stimulation is given at a high frequency – Parkinson’s symptoms decrease markedly.

What is the best theory for why DBS works?

Before starting, let me note that reading this part is not critical. It is very technical.

As noted before, we don’t really understand how DBS works. But there are numerous complicated theories.

Let us look at the simplest & most promising one, in relation to DBS of the most common target. The most common target is the Subthalamic Nucleus (STN).

First, let’s see what causes Parkinson’s disease.

1. Usually, Dopamine keeps the STN in check.
2. When Dopamine decreases, the STN runs amok (becomes hyperactive).
3. This causes problems with movement – especially slowness. We recognize these as “Parkinson’s disease”.

What happens when you put a wire into the STN and pass a high-frequency current through it?

1. If you pass high-frequency electrical current into the STN, it cannot keep doing what it is doing. The fast electrical buzz causes it to go into “overload”.
2. The part being stimulated (e.g. the STN) stops working.
3. Gatekeepers in the brain (e.g. a part called the Thalamus) prevent the high-frequency electrical current from spreading to the rest of the brain. Thus, the rest of the brain keeps functioning well.

The other theories are a variation on this theme. Click here for a short table about these proposed mechanisms.

Some DBS effects cannot be explained by this theory.

Many symptoms including tremor and slowness decrease with high-frequency stimulation. But some symptoms like Freezing decrease with low-frequency electrical stimulation.

Why? We don’t know.

Therefore, there is a lot more to discover.

If the mechanism of DBS is not known, why should I consider it!?

Because it works.

Because it is quite safe.

There are many things for which we don’t understand the exact reason. For example, we are still finding out more about the myriad benefits of exercise.

For example – How does exercise improve Mood? We don’t understand that too well. But it is easy to grasp that exercise is good for you.

This what-you-see-is-true evidence is called “Empiric Evidence”.

So, Should I get DBS surgery for Parkinson’s?

“How does DBS work?” is a good question. “Should I get DBS?” is a separate question.

The success rate of DBS is quite high. If the patient is properly selected, most of them benefit from it. You can read more about DBS patient criteria here [DBS patient criteria].

In addition to the correct patient, the proper target (STN versus GPi) needs to be selected. [DBS location]

Most patients get at least 4.5 additional good hours. You can read more about DBS success rates by clicking here. [DBS success rate]

The risks of DBS surgery are low. You can read more about the risks by clicking here. [DBS risks]

One of the main barriers to DBS surgery is cost. Thankfully, it is cheaper to DBS surgery in India. You can read more about DBS cost in India and other specifics here. [DBS in India]