Since November 2021, rebates for repetitive Transcranial Magnetic Stimulations (rTMS) have become available for the prescription and delivery of up to 35 sessions (initial treatment course) and for the prescription and delivery of a retreatment course for patients experiencing improved symptoms during initial treatment course but with subsequent relapse in illness of up to 15 sessions.
It is rebated for patients over the age of 18 with major depressive disorder, who have tried at least two classes of antidepressants and remain unwell, and who have not received rTMS therapy previously.
The history of rTMS dates back to the 1790s in a number of bioelectricity experiments. Galvani and Volta, considered the forefathers of electrophysiology, discovered that nerves can carry electrical energy deep within the nervous system. In the 1830s, Michael Faraday was influential in introducing the idea of electromagnetic fields, and this idea expanded 50 years later to showing that low-intensity electrical stimulation to the brain revealed that the cortex held a specific map for motor functions.
In the 1960s, magnetic fields were being used by scientists to stimulate human muscles, and, in 1985, Dr Anthony Barker created the first transcranial magnetic stimulation device.
He proved the ability of magnetic stimulation to influence the motor cortex by using a magnetic field to alter the brain’s electrical signals in this area and producing localised activation of the first dorsal interosseous muscle of the hand. This was done by applying TMS to the brain’s motor cortex in the opposite hemisphere, which controls the movements of that particular muscle. This is still how the resting motor threshold is obtained today.
In the 1990s, studies indicated that TMS was a safe and effective treatment for depressive symptoms. The first Australian randomised controlled trials indicating efficacy were conducted in 1997. TMS therapy for depression was approved in Canada in 2003 and by the FDA in 2008.
TMS represents a painless and non-invasive treatment with minimal effects on a person’s daily routine.
The patient sits in a chair with a magnetic coil placed adjacent to their dorsolateral prefrontal cortex. The coil creates a magnetic field inducing tiny electrical currents in targeted regions of the brain. These electrical currents (also known as eddy currents) are then able to enhance the activity and signalling in the prefrontal cortex, which strengthens its ability to communicate and function with other areas of the brain that regulate mood.
There are several major contraindications when considering patients for rTMS – a history of a seizure disorder, the presence of ferrous metal in the skull or brain, or the patient having a magnetically programmable medical device such as a pacemaker.
Side effects of treatment are generally mild and improve shortly after an individual session and, if present, decrease in incidence over the course of treatments. They include headache, mild scalp discomfort at the site of stimulation, tingling, spasms or twitching of facial muscles (during the stimulation), and light-headedness. Serious side effects are rare and include seizures and mania (particularly in people with bipolar disorder). The referral process for rTMS should involve pre-screening to exclude these contraindications.
Electroconvulsive therapy (ECT) is another form of neurostimulation treatment that is well known and has proven efficacy for the management of depression particularly for severe depressive symptoms. While ECT is a safe and effective treatment for depressive symptoms, rTMS is less invasive and has a distinctly favourable side effect profile in comparison (including the patient being able to return to their daily activities immediately following a treatment).
Most rTMS devices use a coil shaped like a figure-eight to deliver a shallow magnetic field that affects more superficial neurons in the brain. The H-coil allows more widespread activation and a deeper magnetic penetration to structures such as the insula and is used in disorders such as obsessive compulsive disorder (studies are underway examining efficacy in disorders such as Anorexia Nervosa).
At present, the RANZCP guidelines endorse the use of rTMS for major depressive disorder, schizophrenia (for auditory hallucinations), and obsessive compulsive disorder. TMS has also shown potential in other presentations including post-traumatic stress disorders, autism spectrum disorder, substance dependence, tinnitus and chronic pain disorders.
Key messages
- rTMS is an effective, non-invasive treatment option for depression with a favourable side-effect profile in those suitably pre-screened
- Contraindications for rTMS include a history of seizure disorder, intracranial ferromagnetic items, or magnetically programmed devices
- Further indications for the use of rTMS are currently being examined.
Author competing interests – nil