There are a number of medical conditions where symptoms in the body occur because of an abnormal activity of the brain. Parkinson’s disease (PD) is one example. The loss of dopaminergic cells deep in the brain causes abnormal electrical activity in other regions. This abnormal electrical activity results in the movement symptoms of Parkinson’s disease (such as tremor, slowness, and rigidity). If this abnormal activity is stopped, movement can improve.

Deep Brain Stimulation (DBS) has been performed for over 30 years and is an established way of “turning off”, or neuromodulating, a small area of the brain. It is currently not fully understood how DBS works but it has been shown to directly impact brain activity in a controlled way. It involves placing an electrode(s) into the target brain region. Instead of destroying the area, high frequency electrical stimulation are used to stimulate the targetted area. The electrode(s) are connected by a subcutaneous wire to a neural stimulator (sometimes called a “brain pacemaker”) that sits under the skin, usually in the chest. When electrical pulses are produced by the neural stimulator and sent to the tip of the electrode(s), the brain cells in this region are disrupted, providing symptom relief for people with Parkinson’s disease.

The neurostimular can be adjusted to maximize the benefits (turning off the malfunctioning area), and minimize the side effects (turning off adjacent important areas). That is the greatest strength of DBS – it can be adjusted to maximally benefit an individual patient and if there are unwanted side effects, it can be turned down.

In summary, patients with Parkinson’s disease have areas of their brain that are overactive, and DBS electrode(s) can be placed in those areas to correct the brain activity. This may be a confusing concept for some, because everyone has been told that PD is due to a loss of the dopamine brain cell. Loss of this cell can result in abnormal activity in other brain regions, and placing electrodes in those areas can stop the abnormal activity.

When should one consider DBS?

DBS surgery is reserved for those patients who are having motor complications despite best medical management. This includes unacceptable side effects from their medications (such as dyskinesia or abnormal writhing movements), motor fluctuations (where the medication only works for a brief time before wearing off), or tremors that do not respond to medication. It is covered by insurance. If you are doing well on your medications, you may not want to have surgery.

What makes someone a good candidate for DBS?

DBS is performed on those for whom the following motor symptoms do not respond to optimal medications:

• Motor fluctuations
• Dyskinesia, or
• Tremor

What are the benefits of DBS?

The benefits of DBS are directly related to the surgical target. Targeting the thalamus can reduce tremor approximately 80-100%. Targeting the pallidum can reduce dyskinesia approximately 80-100%. Targeting the subthalamic nucleus can reduce motor fluctuations. The details are best reviewed with your neurosurgeon, and, of course, vary from patient to patient. Often, patients can expect the result to be similar to when they are in their best “on” time. If patients experience symptoms that do not respond to levodopa (for example freezing, swallowing, speech difficulty, or balance problems), these will not improve after DBS.

Does DBS improve non-motor symptoms?

DBS is not performed to improve the non-motor symptoms of PD. These include, but are not limited to, dementia, depression, loss of smell, constipation, bladder dysfunction, imbalance (this is complicated, and can be improved in some), impulse control (also complicated, and potentially improved), and REM sleep disorders. Some symptoms, such as anxiety, pain, and sleep, can improve in some people. However, this is variable and should not be expected. Many people will experience some weight gain after DBS.

What are the potential complications of DBS?

The rare but devastating complications, like with other surgeries, are stroke or death. The most common complication is infection. This can be treated with antibiotics but may require the DBS device to be removed until the infection is cleared. There can be temporary stimulation-induced side effects that can be corrected by adjusting the stimulation. These side effects can include personality and behaviour changes. As a result, operations are only done on patients who have a reliable carepartner to accompany them to the clinic after surgery, and report any changes in personality, because the patient themselves may not be aware of the changes.

Do the benefits of DBS last forever?

The electrodes in the brain stay forever but if you have a regular battery operated neurostimular it will eventually run out of power, and will need to be changed approximately every 3 years (2-7 year range). There are also options for neurostimulators that have rechargeable batteries and can last up to 15 years.

The effects of DBS continue forever, but new symptoms may develop that are not controlled by the DBS. For example, if a patient develops dementia years after their DBS surgery, the device will not be able to help this. The patient’s quality of life will then deteriorate because of the new dementia, not because the DBS stopped working. Deep brain stimulation does not slow down or prevent the disease from progressing.

Post-surgery, will follow-up appointments happen on a regular basis, and can the patient control the device themselves?

During surgery, the DBS is implanted but left turned off. Patients then return to the DBS Clinic to have the device turned on after six weeks. Initially, there are weekly appointments to find the best settings. Safe limits are set, within which the patient or carepartner can adjust the stimulation. Later, follow-ups are scheduled every 6-12 months to see how the patient is doing, and to plan for battery replacements as needed.

Who is a poor candidate for DBS?

1. Those with a diagnosis of an atypical parkinsonian syndrome (e.g. progressive supranuclear palsy, multiple system atrophy, dementia with Lewy bodies, corticobasal degeneration, or vascular parkinsonism). These people are often referred for DBS because of poor response to medical therapies, but unfortunately, typically do not respond well to the surgery.
2. People with PD whose primary goals are to improve speech, respiratory and pharyngeal control, postural instability (history of falling), and freezing. Several long-term studies have shown that these dopaminergic-resistent symptoms continue to progress despite changes in stimulation parameters and improvement of other motor symptoms, such as tremor, rigidity, and bradykinesia.
3. People with more than mild cognitive dysfunction, active psychiatric disease, dementia, or significant cognitive impairment. This is mostly due to reports of cognition in PD worsening irreversibly after DBS surgery in patients with pre-existing cognitive impairment. Most centres use detailed neuropsychological testing to screen for dementia.
4. People who are not able or do not have the ability for adequate follow-up. If the patient cannot get to the DBS clinic postoperatively, it is impossible to adjust the DBS appropriately. If a patient is in a nursing home, for example, it is very difficult for the DBS clinic to teach every single nurse how to adjust the stimulator at the beginning which increases the risk of misuse of the stimulator.

Sources

Honey, C. (2019). Deep Brain Stimulation. Retrieved from http://drhoney.org/dbs

This help sheet was produced in collaboration with Dr. Christopher Honey and Dr. Stefan Lang. Last updated: January 9, 2025