Brain stimulation therapies can play a role in treating certain mental disorders. Brain stimulation therapies involve activating or inhibiting the brain directly with electricity. The electricity can be given directly by electrodes implanted in the brain, or noninvasively through electrodes placed on the scalp. The electricity can also be induced by using magnetic fields applied to the head. While these types of therapies are less frequently used than medication and psychotherapies, they hold promise for treating certain mental disorders that do not respond to other treatments.
Electroconvulsive therapy is the best studied brain stimulation therapy and has the longest history of use. Other stimulation therapies discussed here are newer, and in some cases still experimental methods. These include:
- vagus nerve stimulation (VNS)
- repetitive transcranial magnetic stimulation (rTMS)
- magnetic seizure therapy (MST)
- deep brain stimulation (DBS)
Electroconvulsive therapy (ECT) uses an electric current to treat serious mental disorders. This type of therapy is usually considered only if a patient’s illness has not improved after other treatments (such as antidepressant medication or psychotherapy) are tried, or in cases where rapid response is needed (as in the case of suicide risk and catatonia, for example).
ECT: Why it’s done
ECT is most often used to treat severe, treatment-resistant depression, but it may also be medically indicated in other mental disorders, such as bipolar disorder or schizophrenia. It also may be used in life-threatening circumstances, such as when a patient is unable to move or respond to the outside world (e.g., catatonia), is suicidal, or is malnourished as a result of severe depression.
ECT can be effective in reducing the chances of relapse when patients undergo follow-up treatments. Two major advantages of ECT over medication are that ECT begins to work quicker, often starting within the first week, and older individuals respond especially quickly.
ECT: How it works
Before ECT is administered, a person is sedated with general anesthesia and given a medication called a muscle relaxant to prevent movement during the procedure. An anesthesiologist monitors breathing, heart rate and blood pressure during the entire procedure, which is conducted by a trained medical team, including physicians and nurses. During the procedure:
- Electrodes are placed at precise locations on the head.
- Through the electrodes, an electric current passes through the brain, causing a seizure that lasts generally less than one minute. Because the patient is under anesthesia and has taken a muscle relaxant, it is not painful and the patient cannot feel the electrical impulses.
- Five to ten minutes after the procedure ends, the patient awakens. He or she may feel groggy at first as the anesthesia wears off. But after about an hour, the patient usually is alert and can resume normal activities.
A typical course of ECT is administered about three times a week until the patient’s depression improves (usually within 6 to 12 treatments). After that, maintenance ECT treatment is sometimes needed to reduce the chances that symptoms will return. ECT maintenance treatment varies depending on the needs of the individual, and may range from one session per week to one session every few months. Frequently, a person who undergoes ECT also takes antidepressant medication or a mood stabilizing medication.
ECT Side Effects
The most common side effects associated with ECT include:
- upset stomach
- muscle aches
- memory loss
Some people may experience memory problems, especially of memories around the time of the treatment. Sometimes the memory problems are more severe, but usually they improve over the days and weeks following the end of an ECT course.
Research has found that memory problems seem to be more associated with the traditional type of ECT called bilateral ECT, in which the electrodes are placed on both sides of the head.
In unilateral ECT, the electrodes are placed on just one side of the head—typically the right side because it is opposite the brain’s learning and memory areas. Unilateral ECT has been found to be less likely to cause memory problems and therefore is preferred by many doctors, patients and families.
Vagus Nerve Stimulation
Vagus nerve stimulation (VNS) works through a device implanted under the skin that sends electrical pulses through the left vagus nerve, half of a prominent pair of nerves that run from the brainstem through the neck and down to each side of the chest and abdomen. The vagus nerves carry messages from the brain to the body’s major organs (e.g. heart, lungs and intestines) and to areas of the brain that control mood, sleep, and other functions.
VNS: Why it’s done
VNS was originally developed as a treatment for epilepsy. However, scientists noticed that it also had favorable effects on mood, especially depressive symptoms. Using brain scans, scientists found that the device affected areas of the brain that are involved in mood regulation. The pulses appeared to alter the levels of certain neurotransmitters (brain chemicals) associated with mood, including serotonin, norepinephrine, GABA and glutamate.
In 2005, the U.S. Food and Drug Administration (FDA) approved VNS for use in treating treatment-resistant depression in certain circumstances:
- If the patient is 18 years of age or over; and
- If the illness has lasted two years or more; and
- if it is severe or recurrent; and
- if the depression has not eased after trying at least four other treatments
According to the FDA, it is not intended to be a first-line treatment, even for patients with severe depression. And, despite FDA approval, VNS remains an infrequently used because results of early studies testing its effectiveness for major depression were mixed. But a newer study , which pooled together findings from only controlled clinical trials, found that 32% of depressed people responded to VSN and 14% had a full remission of symptoms after being treated for nearly 2 years.
VNS: How it works
A device called a pulse generator, about the size of a stopwatch, is surgically implanted in the upper left side of the chest. Connected to the pulse generator is an electrical lead wire, which is connected from the generator to the left vagus nerve.
Typically, 30-second electrical pulses are sent about every five minutes from the generator to the vagus nerve. The duration and frequency of the pulses may vary depending on how the generator is programmed. The vagus nerve, in turn, delivers those signals to the brain. The pulse generator, which operates continuously, is powered by a battery that lasts around 10 years, after which it must be replaced. Normally, people do not feel pain or any other sensations as the device operates.
The device also can be temporarily deactivated by placing a magnet over the chest where the pulse generator is implanted. A person may want to deactivate it if side effects become intolerable, or before engaging in strenuous activity or exercise because it may interfere with breathing. The device reactivates when the magnet is removed.
Please Note: VNS should only be prescribed and monitored by doctors who have specific training and expertise in the management of treatment-resistant depression and the use of this device.
VNS treatment is intended to reduce symptoms of depression. It may be several months before the patient notices any benefits and not all patients will respond to VNS. It is important to remember that VNS is intended to be given along with other traditional therapies, such as medications, and patients should not expect to discontinue these other treatments, even with the device in place.
VNS: Side Effects
VNS is not without risk. There may be complications such as infection from the implant surgery, or the device may come loose, move around or malfunction, which may require additional surgery to correct. Some patients have no improvement in symptoms and some actually get worse.
Other potential side effects include:
- Voice changes or hoarseness
- Cough or sore throat
- Neck pain
- Discomfort or tingling in the area where the device is implanted
- Breathing problems, especially during exercise
- Difficulty swallowing
Long-term side effects are unknown.
Repetitive Transcranial Magnetic Stimulation
Repetitive transcranial magnetic stimulation (rTMS) uses a magnet to activate the brain. First developed in 1985, rTMS has been studied as a treatment for depression, psychosis, anxiety, and other disorders.
Unlike ECT, in which electrical stimulation is more generalized, rTMS can be targeted to a specific site in the brain. Scientists believe that focusing on a specific site in the brain reduces the chance for the types of side effects associated with ECT. But opinions vary as to what site is best.
rTMS: Why it’s done
In 2008, rTMS was approved for use by the FDA as a treatment for major depression for patients who do not respond to at least one antidepressant medication in the current episode. It is also used in other countries as a treatment for depression in patients who have not responded to medications and who might otherwise be considered for ECT.
The evidence supporting rTMS for depression was mixed until the first large clinical trial , funded by NIMH, was published in 2010. The trial found that 14% achieved remission with rTMS compared to 5% with an inactive (sham) treatment. After the trial ended, patients could enter a second phase in which everyone, including those who previously received the sham treatment, was given rTMS. Remission rates during the second phase climbed to nearly 30%. A sham treatment is like a placebo, but instead of being an inactive pill, it’s an inactive procedure that mimics real rTMS.
rTMS: How it works
A typical rTMS session lasts 30 to 60 minutes and does not require anesthesia.
During the procedure:
- An electromagnetic coil is held against the forehead near an area of the brain that is thought to be involved in mood regulation.
- Then, short electromagnetic pulses are administered through the coil. The magnetic pulses easily pass through the skull, and causes small electrical currents that stimulate nerve cells in the targeted brain region.
Because this type of pulse generally does not reach further than two inches into the brain, scientists can select which parts of the brain will be affected and which will not be. The magnetic field is about the same strength as that of a magnetic resonance imaging (MRI) scan. Generally, the person feels a slight knocking or tapping on the head as the pulses are administered.
Not all scientists agree on the best way to position the magnet on the patient’s head or give the electromagnetic pulses. They also do not yet know if rTMS works best when given as a single treatment or combined with medication and/or psychotherapy. More research is underway to determine the safest and most effective uses of rTMS.
rTMS: Side Effects
Sometimes a person may have discomfort at the site on the head where the magnet is placed. The muscles of the scalp, jaw or face may contract or tingle during the procedure. Mild headaches or brief lightheadedness may result. It is also possible that the procedure could cause a seizure, although documented incidences of this are uncommon. Two large-scale studies on the safety of rTMS found that most side effects, such as headaches or scalp discomfort, were mild or moderate, and no seizures occurred. Because the treatment is relatively new, however, long-term side effects are unknown.
Magnetic Seizure Therapy
MST: How it works
Magnetic seizure therapy (MST) borrows certain aspects from both ECT and rTMS. Like rTMS, MST uses magnetic pulses instead of electricity to stimulate a precise target in the brain. However, unlike rTMS, MST aims to induce a seizure like ECT. So the pulses are given at a higher frequency than that used in rTMS. Therefore, like ECT, the patient must be anesthetized and given a muscle relaxant to prevent movement. The goal of MST is to retain the effectiveness of ECT while reducing its cognitive side effects.
MST is in the early stages of testing for mental disorders, but initial results are promising. A recent review article that examined the evidence from eight clinical studies found that MST triggered remission from major depression or bipolar disorder in 30-40% of individuals.
MST: Side Effects
Like ECT, MST carries the risk of side effects that can be caused by anesthesia exposure and the induction of a seizure. Studies in both animals and humans have found that MST produces
- fewer memory side effects
- shorter seizures
- allows for a shorter recovery time than ECT
Deep Brain Stimulation
Deep brain stimulation (DBS) was first developed as a treatment for Parkinson’s disease to reduce tremor, stiffness, walking problems and uncontrollable movements. In DBS, a pair of electrodes is implanted in the brain and controlled by a generator that is implanted in the chest. Stimulation is continuous and its frequency and level are customized to the individual.
DBS has been studied as a treatment for depression or obsessive compulsive disorder (OCD). Currently, there is a Humanitarian Device Exemption for the use of DBS to treat OCD, but its use in depression remains only on an experimental basis. A review of all 22 published studies testing DBS for depression found that only three of them were of high quality because they not only had a treatment group but also a control group which did not receive DBS. The review found that across the studies, 40-50% of people showed receiving DBS greater than 50% improvement.
DBS: How it works
DBS requires brain surgery. The head is shaved and then attached with screws to a sturdy frame that prevents the head from moving during the surgery. Scans of the head and brain using MRI are taken. The surgeon uses these images as guides during the surgery. Patients are awake during the procedure to provide the surgeon with feedback, but they feel no pain because the head is numbed with a local anesthetic and the brain itself does not register pain.
Once ready for surgery, two holes are drilled into the head. From there, the surgeon threads a slender tube down into the brain to place electrodes on each side of a specific area of the brain. In the case of depression, the first area of the brain targeted by DBS is called Area 25, or the subgenual cingulate cortex. This area has been found to be overactive in depression and other mood disorders. But later research targeted several other areas of the brain affected by depression. So DBS is now targeting several areas of the brain for treating depression. In the case of OCD, the electrodes are placed in an area of the brain (the ventral capsule/ventral striatum) believed to be associated with the disorder.
After the electrodes are implanted and the patient provides feedback about their placement, the patient is put under general anesthesia. The electrodes are then attached to wires that are run inside the body from the head down to the chest, where a pair of battery-operated generators are implanted. From here, electrical pulses are continuously delivered over the wires to the electrodes in the brain. Although it is unclear exactly how the device works to reduce depression or OCD, scientists believe that the pulses help to “reset” the area of the brain that is malfunctioning so that it works normally again.
DBS Side Effects
DBS carries risks associated with any type of brain surgery. For example, the procedure may lead to:
- Bleeding in the brain or stroke
- Disorientation or confusion
- Unwanted mood changes
- Movement disorders
- Trouble sleeping
Because the procedure is still being studied, other side effects not yet identified may be possible. Long-term benefits and side effects are unknown.