Transcranial magnetic stimulation or TMS is a non-invasive, diagnostic and therapeutic technique that uses small magnetic fields to stimulate or inhibit regions of the brain by electromagnetic induction through a small generator coil (Figure-8 or H-coil), placed over the patient's head. It can be used for the treatment of conditions such as depression and obsessive-compulsive disorder (OCD).
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TMS delivers magnetic pulses to certain brain regions, producing changes in the activity of the brain cells. The frequency of pulse delivery influences whether brain activity is increased or decreased in the affected cells. This means that the effects of TMS treatment can be long lasting because it changes the patterns by which nerve cells and brain networks connect and communicate with each other.
Every patient is different. Most large TMS research studies provided treatment five days a week for 4-6wks up to 36 sessions for a figure of 8 coil treatment. H-coil treatments have been studied for 5 days a week of treatment followed by 12 weeks of treatment 2 times a week for a total of 44 sessions. There is no demonstrated toxicity from treatment beyond this amount of sessions and, in some situations, it may be reasonable to continue treatments beyond this number. Some people may require a schedule of maintenance treatments to maintain their treatment results.
Both TMS and ECT are forms of neuromodulation used to treat depression. Electro-convulsive therapy (ECT) involves passing an electric current through the brain. This causes a generalized (grand mal) seizure. It therefore requires a general anesthetic. While having ECT, patients may require inpatient care or require someone to drive them to and from ECT treatments. ECT can cause short term memory loss for the period before and after each treatment session. Patients usually have 6-12 treatment sessions over three to six weeks and few patients have memory loss for this whole time period.
TMS uses an electromagnetic coil to create an alternating magnetic field over the scalp and this magnetic field induces small currents in the brain.
TMS is an outpatient procedure that does not require an anesthetic and patients can resume their normal life activity after the session.
Both TMS and ECT can lead to a rapid improvement in symptoms. Up to 70% of depressed patients who fail to respond to antidepressants respond to ECT and about 60% of patients who fail to respond to antidepressants respond to TMS.
Some patients who fail to respond to ECT will respond to TMS and some patients who fail to respond to TMS will respond to ECT. ECT is still considered the best treatment for some patients with very severe depression, psychotic depression or catatonia. Your doctor will advise you about which is the best treatment for you.
Antidepressants work by modifying the actions of neurotransmitters (brain chemicals) or modifying neurotransmitter receptors. TMS induces small electrical currents in the brain which improve the connections between brain cells and increase the growth of brain cells. Treatment with antidepressants involves taking medications which are absorbed through the mouth, stomach and small intestine with possible side effects throughout the body. They can cause adverse effects such as gastrointestinal side effects weight gain and can have an effect on sexual function (reduced sex drive and delayed ejaculation). Patients can also be allergic to antidepressants or other chemicals contained in the medication.
TMS does not involve the ingestion of chemicals, therefore, there are no systemic adverse effects. There is no impact on the digestive system, on sexual function, cognition and there are no allergic responses. The only side effect with TMS that is greater than 5% is transient site pain, headache which abates typically within the first week as patients desensitize to the treatment.
Antidepressants modify brain chemicals and receptors via an effect on protein synthesis, they can take between three to six weeks to work, while TMS has a faster onset of action. Studies show that in patients who have not responded to two or three antidepressants the response rate the next antidepressant is 10-15%. If such patients are given TMS, the response rate is about 60%.
Your doctor will discuss with you the best way to administer TMS. The session lasts between three and 37 minutes depending on the protocol used.
TMS can be very effective in the treatment of depression. For over 20 years it has demonstrated the ability to improve depression symptoms in patients in research studies as well as under more real-world conditions. In one of the largest studies of patients treated with TMS for depression, around 60% of participants reduced their symptoms by at least 50% (responded) and around 30% of participants no longer met criteria for depression (remitted). This study did include some participants who have been treated with ECT to manage their symptoms and they had equal chances to achieve improvement compared to people who had not had ECT in the past. TMS is effective in the treatment of obsessive-compulsive disorder (OCD) as well. Around 40% of participants in the landmark study for FDA (Food and Drug Administration) clearance achieved remission and around 60% of participants responded to treatment. This is just a sample of some of the illnesses that TMS has been demonstrated to effectively treat but there are other illnesses that are under investigation or approved in countries outside of the United States including PTSD, stroke rehabilitation, and chronic pain.
TMS has been tried as a treatment for different mental health and neurological conditions such as, depression, obsessive compulsive disorder (OCD), post traumatic stress disorder (PTSD), anxiety, addiction, eating disorders, dementia, autism, migraine, neuropathic pain, fibromyalgia, post stroke conditions … etc. However, the current evidence to support the use of TMS in treating different conditions vary significantly. At the present time there is very strong evidence to support the use of TMS as a treatment for depression. This led to TMS being used in the treatment of depression in many countries around the world. For example, in 2008 the FDA approved the first TMS machine for the treatment of depression and in 2015 NICE (National Institute for Health and Care Excellence) in the UK recommended TMS as a treatment for depression. The FDA also approved some TMS devices to be used for the treatment of OCD and Migraine. The evidence supporting the use of TMS as a treatment for different mental health and neurological conditions is growing very quickly. Therefore, we advise you to check with your treating doctor if TMS could be a possible treatment option for your condition. You can find a TMS clinician in your local area by checking find a provider page on our website.
The most common side effects of TMS are discomfort at the site of treatment during the treatment sessions and a mild headache for a few hours following the sessions. Occasionally patients experience discomfort in the eye, teeth or jaw and typically alleviated with over the counter analgesics.
Some patients may experience increased anxiety and sleep difficulties. All of these usually decrease following the first week of treatment.
TMS is a loud treatment, wearing appropriate ear plugs during sessions protects hearing. There is a very small risk that some patients will develop seizures during treatment sessions. The probability of a patient without a history of epilepsy developing seizures is 1 per 60,000 treatment sessions. This is less than the risk of seizures developing in patients who take antidepressants.
It is advisable that you have regular follow-ups with your treating clinician after you respond to TMS. This should help to consolidate your recovery and in order to agree on a treatment plan if you start having depressive symptoms again. A lot of patients who respond to TMS maintain their improvement without having additional treatments for at least a year. However, there is a group of patients who might re-experience depressive symptoms after responding to TMS. For this group of patients, the treating clinician might decide to reintroduce TMS. These are sometimes called booster or rescue TMS and if you responded to your initial course of TMS it is highly likely you will respond to TMS again. In addition, if TMS is reintroduced sooner in the onset of depression, typically patients require fewer TMS booster sessions to stabilize their mood. Some patients might need to have what we call maintenance TMS sessions. This involves the patient having regularly scheduled TMS sessions once every few weeks in order to maintain mood stability. The frequency of these maintenance TMS sessions is usually decided after a discussion between the patient and their treating clinician while taking different factors into account. Your treating clinician might also suggest prescribing you medication (such as an antidepressant) to consolidate your recovery, deal with recurrence of symptoms or to protect you against relapsing.
In summary, a good proportion of patients who respond to TMS maintain their improvement without further interventions and for patients who re-experience depressive symptoms TMS can still help them to overcome these symptoms.
Around 60% of people treated with TMS respond to treatment. If people do not respond to TMS they should be evaluated by their treating psychiatrist and other treatments should be considered. This should include medication review, ECT and psychotherapy. Some patients will improve using different TMS sequences or treatment locations.
TMS is a well-tolerated treatment, the vast majority of patients can have TMS. People with non-removable metallic, ferromagnetic objects which is less than 30 cm from the treatment coil might not be suitable for TMS and should consult with their TMS prescriber if they have any of these items:
- implanted electrodes
- aneurysm clips or coils
- cochlear implants
- stents in the head
- metal fragments
TMS can still be given to people with certain types of stents and implants. People with implanted cardiac defibrillators cannot have TMS. Dental work including fillings/implants and piercings are not a contraindication for TMS.
The time needed for a patient to start seeing positive results differs from one patient to the other and it is quite difficult to predict. Assuming that patients have daily sessions for five days every week the majority of patients who respond to TMS start seeing positive results after a few weeks of receiving the treatment. However, some patients report positive results sooner than this and other patients can have a delayed response that at times happens towards the end of the 6th week of TMS treatment.