This information is for people who have Parkinson's disease. It tells you about subthalamotomy, a treatment used for Parkinson's. It is based on the best and most up-to-date research.
Does it work?
We're not sure. There hasn't been enough research on subthalamotomy so we can't say whether it works. And this type of brain surgery can be dangerous. Doctors don't often do this type of surgery any more because it's too risky, and there are safer methods now.
What is it?
Subthalamotomy destroys cells in a part of your brain called the subthalamic nucleus. The aim is to reduce your symptoms of Parkinson's and the uncontrolled movements that can happen if you've been taking the drug levodopa for a long time.
Subthalamotomy is just one type of surgery for Parkinson's disease. To learn about the others, see Brain surgery .
Before the operation, your surgeon will use something called stereotactic technology to pinpoint the part of your brain that needs treatment.  Here's how it works.
A frame is fixed to your head with four pins to keep it still. You'll be given a local anaesthetic so you'll be awake but it won't hurt.
Your surgeon will then create a detailed picture (map) of your brain using one of two types of scans: magnetic resonance imaging (MRI) or computed tomography (CT).
They will then use computer software to find a path through your brain to the exact spot that needs to be treated.
After your surgeon has found the part of your brain that needs treatment, they will:
When the tip of the electrode reaches its target, your surgeon will take electrical readings to pinpoint the target exactly. They will use electrical energy to destroy some brain cells. To do this, they will heat up the electrode to about 85 degrees Celsius (185 degrees Fahrenheit) to burn the brain cells away.  Then your surgeon will remove the electrode from your brain.
The operation can take up to eight hours, and you'll need to stay in hospital for about a week. You should be able to see the effects of the operation as soon as you wake up.
A subthalamotomy is not reversible (the brain cells are killed). And this operation is rarely done because of serious risks.
Brain surgery is difficult and things can go wrong. Before you decide to have surgery, you should talk to your surgeon about problems that can happen and how likely you are to get these problems. 
How can it help?
We're not sure how having subthalamotomy might help you if you have Parkinson's disease. There hasn't been enough research on this type of surgery.