One of the most challenging goals for a surgeon implanting a deep brain stimulation device is to safely implant the electrode in the precise target location within the brain. Because not everyone's brain is shaped the same, the task of locating and accessing a specific brain structure without disturbing the surrounding structures requires the use of special tools and techniques.
One standard tool that is used for most delicate brain surgeries is a stereotactic frame. This device is basically a metal structure that holds the patient's head very still and gives the doctors a stable starting point to make their measurements. The surgeon will also rely on sophisticated imaging techniques to help pinpoint the location of specific structures within the brain. For example, the surgeon may rely on magnetic resonance imaging (MRI) or computerized tomography (CT scan) imaging, which can both be loosely thought of as three-dimensional X-ray scans.
The best way for the surgeon to be sure that the electrode is in the right place is to turn on the device and observe its effects on the patient's symptoms. For this reason, the patient is usually kept awake for the electrode implantation portion of the surgery. Because the brain itself has no pain receptors, the patient won't feel any pain. Only local anesthesia is required to numb the location where a small hole is made in the skull. The patient will also be required to discontinue the use of all medications prior to the surgery. This requirement is so that the effects of the electrical stimulation alone on the disease symptoms can be observed.
After the electrode is firmly in place, the pulse generator is implanted elsewhere in the patient's body where there's more space. Usually, this is in a location within the patient's chest. Since there's no longer any need for the patient to be awake, the patient is placed under general anesthesia for this part of the surgery. One other step involved in the surgery is to tunnel a wire under the skin from the pulse generator to the electrode in the brain.
Several days after the surgery, the doctors switch on the deep brain stimulation device and program it to suit the individual needs of the patient. Different aspects of the electrical stimulation pattern, such as its pulse strength, shape and frequency, can be adjusted as necessary. The patient is also required to come in every few months so that doctors can adjust this pattern to ensure optimal performance of the device.