What Is Transcranial Magnetic Stimulation

Introduction

In 1985, transcranial magnetic stimulation (TMS) was first introduced as a therapeutic tool. Since then, TMS has been subject to various studies exploring its potential uses in the treatment of a range of conditions, specifically mental and neurological. 

Ultimately, the underlying therapeutic potential of TMS is that it functions to alter the activity of areas of the brain, specifically the mood areas, which is done by passing an electric current through a coil to generate a magnetic field. 

Since the introduction of TMS, the therapy has undergone several modifications, a key one being known as repetitive TMS. This involves repetitive pulses of an electric current applied in short intervals, which can be high frequency or low frequency to stimulate or inhibit the brain, respectively. 

Repetitive TMS has also been modified to develop theta burst stimulation, which can provide greater stimulation for the brain in shorter periods of time. Intermittent theta burst stimulation is used in sessions lasting three and a half minutes, and is much shorter than the sessions for repetitive TMS, which last just over half an hour. 

Although TMS has undergone several developments, the therapy’s subtypes have a shared function: using electricity and electromagnetic fields to change the activity of areas of the brain to treat mental and neurological conditions.^1,2,3,4

How transcranial magnetic stimulation works

TMS is based on a principle known as electromagnetic induction, which is when an electric current is passed through a coil to generate a magnetic field. With TMS, this leads to alterations in the activity of the brain. It is mostly used when targeting mood disorders such as depression, OCD, and Parkinson’s disease. 

Before you can start TMS, you’ll first need to have: 

• A mental health assessment
• A physical exam
• Blood tests

These will let your healthcare professional know that TMS is the right option, and undergoing TMS won’t harm you in any way. It doesn’t involve any type of anaesthesia and is generally given as an outpatient procedure.

The first appointment will generally last for an hour and is known as the mapping process. You’ll normally sit comfortably in a reclining chair while the person carrying out the treatment will identify the best magnet placement, as well as how much magnetic energy you’ll need. This placement is only done once, with further treatments using the measurements acquired from the first procedure.

Applications of transcranial magnetic stimulation

TMS is mostly used for the treatment of mental and neurological diseases, as these conditions can involve disruption to various regions of the brain that TMS can act on. Most commonly treated is depression, obsessive-compulsive disorder, Parkinson’s disease, though other conditions, such as Alzheimer’s disease, schizophrenia, and substance-use disorders, may be able to be treated with TMS too.³

Depression

Depression is a mental disorder that causes persistent feelings of sadness and a loss of interest. Accompanying this may be feelings of emptiness, irritability, and impaired cognition, which can make it much more difficult to go about typical day-to-day activities. 

• With depression, you may experience physical signs and symptoms, too, such as Appetite and weight changes.
• Sleep disturbances
• Fatigue 
• Most severely, depression can increase the risk of having suicidal thoughts and suicide.

The NHS has outlined several resources that you can reach out to if you are struggling with suicidal thoughts.⁵

Obsessive-compulsive disorder

Obsessive-compulsive disorder is a disorder characterised by obsessions and compulsions. Obsessions are:

• Intrusive
• Unwanted thoughts
• Impulses 

These obsessions can lead to compulsions, which are behaviours someone feels driven to act out, often to overcome the discomfort caused by obsessions. 

Common obsessions and compulsions include: 

• Concerns about hygiene
• Causing harm to oneself or others
• Intrusive, aggressive or sexual thoughts
• The symmetry, ordering, and organisation of things 

Most patients with obsessive-compulsive disorder are aware that they have obsessions and compulsions and have a desire to have control over them.⁶

Parkinson’s disease

Parkinson’s disease is a condition resulting from degeneration of the brain that tends to occur as one age. Specifically, the part of the brain that produces dopamine, a chemical associated with movement, cognition, and motivation. 

Signs and symptoms caused by Parkinson’s disease typically impact movement and include:

• Tremors
• Rigidity
• Slow movements

However, the condition can also impact people beyond their movement, with effects such as: 

• A loss of smell 
• Difficulty passing stools
• Depression^{7, 8}

The procedure of transcranial magnetic stimulation

TMS is performed in a treatment room where you will sit in a reclining chair and be given earplugs to wear for the duration of the session. Following this, a coil will be placed on your head and switched on and off to produce pulses. These pulses will cause you to feel a sensation of tapping on your forehead. Depending on the form of TMS being used, this session can last from a few minutes to half an hour.⁹

Risks and benefits of transcranial magnetic stimulation

TMS is a safe procedure that does not carry many risks. However, the most common complication of TMS is seizures. For patients without epilepsy, the risk of seizures is less than 0.01 per cent per session. However, for patients with epilepsy, the risk of seizures is higher, being less than three per cent per session. TMS can also result in several less serious complications:⁹

• Headaches
• Neck pain
• Buzzing or ringing in the ears
• Reduced tolerance to sound

Due to the magnets involved, TMS is not recommended for people who have metal devices in their bodies, such as:

• Hearing aids
• Pacemakers
• Stents
• Bullet fragments

Summary

Transcranial magnetic stimulation (TMS) is a treatment that can be used to treat several mental and neurological conditions, mostly depression, obsessive-compulsive disorder, and Parkinson’s disease. 

This therapy involves the passage of an electric current through a wire to alter the activity of the brain, to stimulate or inhibit it, treating conditions characterised by altered activity of the brain. 

TMS is a safe procedure and does not pose many risks. However, the most common complication of TMS, though still rare, is seizures, which are more likely to occur in patients with epilepsy. 

FAQs

What conditions can TMS treat?

TMS can treat a multitude of conditions, such as:

• Depression
• Obsessive-compulsive disorder
• Parkinson’s disease
• Alzheimer’s disease
• Schizophrenia
• Substance use disorders such as smoking

TMS continues to be researched, increasing the variety of mental and neurological conditions that can be treated with TMS.³

Is TMS a safe procedure?

TMS is a safe procedure that doesn’t pose many risks. The most serious potential complication of TMS is seizures, though these are likelier to occur in patients with epilepsy. Other possible side effects include:

• Headaches
• Neck pain
• Buzzing or ringing in the ears
• Reduced tolerance to sound⁹

How long does a typical TMS session last, and how many sessions are usually needed?

The length of a typical session of TMS varies depending on the subtype of TMS, where repetitive TMS may take half an hour per session, and theta burst stimulation may only last a few minutes per session. How many sessions are usually needed can vary depending on the condition being treated.²

How effective is TMS in treating depression and other mental disorders?

TMS can treat forms of depression that have not responded to other types of treatment, such as medication and talk therapy. TMS has also commonly been used in the treatment of obsessive-compulsive disorder. 

The potential of TMS as a treatment for other mental disorders has been demonstrated, including for post-traumatic stress disorder, generalised anxiety disorder, bipolar disorder, schizophrenia, and substance-use disorder.^{3 9}  

Are there any contraindications for undergoing TMS?

Patients with epilepsy face a higher risk of having seizures following TMS so they may be advised not to undergo TMS.⁹

Can TMS be used in combination with other treatments?

TMS can be used in combination with other treatments, including medications.⁹