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Transcranial magnetic stimulation
By Mayo Clinic staffMayo Clinic Health Manager
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Definition
Transcranial magnetic stimulation is a procedure that uses magnetic fields to stimulate nerve cells in the brain to improve symptoms of depression. Transcranial magnetic stimulation is one of the newer types of brain-stimulation methods designed to treat depression when standard treatment hasn't worked.
There are different ways to perform transcranial magnetic stimulation. But in general, a large electromagnetic coil is placed against your scalp near your forehead. The electromagnet creates painless electric currents that stimulate nerve cells in the region of your brain involved in mood regulation and depression.
Why it's done
Depression is usually a treatable condition. Often, standard treatment with antidepressant medications, psychotherapy or electroconvulsive therapy can help improve even severe cases of depression.
An option when standard approaches haven't worked
Transcranial magnetic stimulation is usually used when standard depression treatments don't work. In the United States, it's not recommended as the first treatment option.
Transcranial magnetic stimulation is not widely available yet in the United States, but more physicians and medical centers are beginning to use it. In other countries where transcranial magnetic stimulation is used to treat depression, it's typically used only for people with depression that hasn't improved with standard treatments or for those who may be considering electroconvulsive therapy but want an alternative.
How it works
It's not clear precisely how transcranial magnetic stimulation may help relieve symptoms of depression. Networks of brain regions may play a role in mood regulation. Stimulating the brain in these regions may change how the brain functions and may lead to mood improvement.
During transcranial magnetic stimulation, the magnetic pulses create painless electrical currents in your brain. These currents stimulate nerve cells in the region of your brain involved in mood regulation and depression. In some types of transcranial magnetic stimulation, brain activity is suppressed. In other types, brain activity is increased.
Researchers are still trying to determine the best dosage of stimulation and the best area of the brain to stimulate. The amount of stimulation can be changed depending on your symptoms and side effects.
Risks
Transcranial magnetic stimulation is the least invasive of the brain-stimulation procedures used for depression. It requires no surgery or implantation of electrodes or nerve stimulators. While it's considered generally safe, it's not without some risks.
Common side effects
Common side effects and adverse health problems associated with transcranial magnetic stimulation include, but may not be limited to:
- Headache
- Scalp discomfort at the site of stimulation
- Tingling, spasms or twitching of facial muscles
- Lightheadedness
- Discomfort from noise during treatment
Uncommon side effects
In rare cases, transcranial magnetic stimulation may also cause more-serious side effects, including:
- Seizure
- Mania
- Hearing problems
Long-term effects unknown
Because transcranial magnetic stimulation involves changes in brain function, unknown long-term adverse health effects are possible. Some studies have shown structural changes in the brain after transcranial magnetic stimulation. The significance of these changes isn't yet known. Also, the long-term effects of exposure to the strong electromagnetic fields involved remain unknown.
How you prepare
Before having the procedure, you may need to have a medical evaluation to make sure it's safe for you and a good option in your case. You may need a full physical and psychiatric evaluation. You should:
- Tell your health provider if you're pregnant or thinking of becoming pregnant.
- Tell your doctor if you have any metal or implanted medical devices in your body. Transcranial magnetic stimulation usually isn't recommended if this is the case.
- Discuss any medications you're taking, including over-the-counter medications, herbal supplements and vitamins. Bring a list of what you're taking, including dosages and how often you take them.
- Tell your doctor if you have a history of seizures.
Transcranial magnetic stimulation isn't invasive, doesn't require anesthesia and can be performed in a doctor's office, so little other preparation is needed. You don't need to arrange for someone to drive you home after treatment.
What you can expect
During transcranial magnetic stimulation
Transcranial magnetic stimulation is usually done on an outpatient basis in a doctor's office or clinic. There are different ways to perform the procedure. Techniques may change as more is learned about the most effective ways to use transcranial magnetic stimulation.
Here's what generally will happen for your first appointment:
- Your first treatment may last about one to two hours. You'll be taken to a treatment room and asked to sit in a reclining chair. The machine makes a loud clicking sound, so you may be given earplugs to wear during the procedure.
- An electromagnetic coil is placed against your scalp on an area near your forehead, often on the left side. To produce the stimulating pulses, the electromagnetic coil is switched off and on repeatedly, sometimes up to 10 times a second. This results in a tapping or clicking sound that usually lasts for a few seconds, followed by a pause. You'll also feel a light tapping sensation on your forehead. This part of the process is called "mapping."
- Your "motor threshold" will be determined. This is the minimum amount of energy needed to make your fingers or hands twitch. The coil is adjusted until the right setting is found.
- After this, your treatment begins.
Most treatment sessions will occur like this:
- While you're sitting in a chair with the magnetic coil placed against your head, the machine is turned on and you'll hear clicking sounds and light tapping on your forehead. You should wear earplugs.
- You'll be awake and alert.
- Some people find the tapping painful, so tell the medical staff if you're uncomfortable.
- Each treatment session lasts about 40 minutes.
After the procedure
Transcranial magnetic stimulation generally requires multiple treatment sessions. Most people require five treatment sessions a week for four to six weeks. After each treatment with transcranial magnetic stimulation, you can go about your normal daily activities.
Results
When transcranial magnetic stimulation works: Symptom relief
If transcranial magnetic stimulation works for you, your depression symptoms could improve or go away completely. This improvement, if it occurs, may be gradual and take a few weeks. Improvement in your mood may last for days or weeks. Some research, however, shows a lack of dramatic improvement in depression symptoms. But as researchers learn more about different techniques, the number of stimulations required and the best sites on the brain to stimulate, the effectiveness of transcranial magnetic stimulation may improve over time.
When transcranial magnetic stimulation may be less effective
Some research suggests that transcranial magnetic stimulation is less effective in certain situations, including:
- Older age
- Presence of psychosis
- Depression that has lasted four or more years
- Failure of electroconvulsive therapy to improve depression symptoms
It's not yet known if transcranial magnetic stimulation can be used to treat depression for the long term, or whether you can have periodic maintenance treatments to prevent depression symptoms from returning.
