Transcranial magnetic stimulation (TMS) is a form of non-invasive brain stimulation. It is administered through a plastic-coated metallic coil that is capable of generating brief but powerful magnetic pulses. When these pulses are delivered to the scalp, they create small amount of electricity in the brain that stimulates nerve cells or “neurons.”
When multiple sessions are administered, TMS is capable of producing lasting changes in the brain. TMS is an approved intervention for a range of conditions, including major depressive disorder (depression), and we have previously found that TMS can benefit social aspects of ASD.
What does TMS feel like?
When undergoing TMS you are awake, alert, and aware of what is happening at all times. A TMS coil is placed against the head (see below), through which TMS is administered. This is connected to a machine that sends an electrical current through the coil. The current produces a magnetic field that is very focused and is able to stimulate electrical activity in nerves below the coil. These are usually nerve cells in the outer layers of the brain.
The sensations associated with rTMS are mild, and most people describe it as a “tapping” sensation on their head. During a rTMS procedure you will hear clicking sounds as the current passes through the coil.
In the current study TMS is administered for around three minutes each weekday for four weeks (20 sessions in total). After TMS you are able to go about your normal daily activities, including driving.
Who can have TMS?
Most people are able to undergo TMS, but there are some instances in which people must not receive TMS. You will not be able to undergo TMS if you have any of the following:
- Metal in your head (except the mouth)
- History of seizure or epilepsy, or evidence of significant seizure activity as assessed by EEG
- History of serious head injury
- Implanted medical device (e.g., cardiac pacemaker, medication pumps)
- Serious heart disease (as there is an increased risk of serious injury in the event of a seizure)
- Unstable medical condition
- Unstable medication regime
- Certain medications
- Substance use disorder
- Employment as a professional driver or machine operator (as the event of a seizure may affect employment)
- Pregnancy or breastfeeding
Is TMS safe?
TMS is generally considered a very safe technique.
The main concern associated with TMS is its potential to induce a fit or seizure. This risk is extremely low, but is increased for those with a history of seizure activity (where a seizure resulting from rTMS affects about 2% or 2 in 100 such individuals). If participants have ever experienced a seizure, or if their EEG shows evidence of epileptiform activity, they will not be able to take part in this study. Investigators using TMS have developed safety guidelines to minimise the risk of seizure. The TMS we provide in the current study is well within what is considered to be safe.
The clicking noise made by the coil may be uncomfortable, but participants wear earplugs during TMS to minimise any discomfort.
A headache can occur during TMS and is thought to affect approximately 3% or 3 in 100 participants. It is thought to be caused by stimulation of nerves in the scalp. If participants experience such a headache from TMS, it will respond quickly to simple pain medication such as aspirin, ibuprofen, or paracetamol.
During TMS, participants might feel a tapping or twitching sensation on their scalp as the magnetic pulse stimulates muscles in their scalp as it passes into the brain. This sensation varies between people from very soft to quite strong. If participants find it uncomfortable, we will use a lower stimulation intensity and only increase it as they find it tolerable.