Repetitive Transcranial Magnetic Stimulation (rTMS)
INTRO ECT MST VNS DBS NEUROSURGERY
Repetitive TMS [1] was approved in the USA in 2008 to treat moderate to severe Difficult-to-Treat -Depression (DTD) and depression with anxiety. It is used in research and is now recommended in NICE guidelines to be introduced into NHS services; but is not widely available. It can be carried out as an outpatient as no general anaesthetic is required. It should be avoided in psychotic or suicidal patients unless they are inpatients on a ward. TMS uses a magnet to activate the brain. Consent is needed from the patient. The treatment is carried out in a clinical setting whilst the patient is awake and alert. The patient wears earplugs to protect them from the clicking sounds the device makes. A magnetic coil is held against the scalp. A magnetic field induces an electric current in a small area of the brain. TMS, unlike ECT, targets a specific area of the brain (involved in mood regulation). Not all scientists agree on the best way to position the magnet or give the electromagnetic pulses. Studies recently have involved using MRI scans of the patient's brain to help determine the positioning of the magnetic coil. The treatment is non-invasive and given by a trained technician. The first treatment is the longest as the technician determines the best site to position the magnets (if an MRI scan hasn’t been taken) and what dose of magnetic energy to use. The level of this varies from patient to patient. Currently, the device is first placed on the scalp above the brain region involved in hand movements and it is noted when the hand starts to twitch (to establish the threshold at which the person’s nerve cells will be stimulated). This should not be painful. The magnet is then placed at the region of the brain involved in depression. No Jewellery should be worn.
Side effects can include mild scalp discomfort and headaches, but these are usually short-lived. The risk of a seizure is very small (less than 1 in 1000); however, the patient may feel faint or dizzy. It is performed in a clinical setting. It has no negative effect on cognitive function/memory. A typical treatment lasts 20-45 mins and is given 5 days a week for 3-6 weeks.
The exact mechanisms of TMS therapy are unclear. There is an increase of blood flow to the brain. The electric current induced in the brain activates cells which release neurotransmitters such as serotonin and dopamine. The current stimulates the inactive or disrupted area of the brain or suppresses the overactive area- reducing the symptoms of depression. It may result in an increase in the production of brain cells (neurones) and it is believed the TMS can stimulate new connections between existing neurones –something called neuroplasticity.
TMS has been shown to be effective in the treatment of depression[1-4]. It is perhaps of most use for patients with more mild depression than those for whom ECT may be used and for patients that cannot take medication. It is not as effective as ECT when treating depression. It may be used to enhance antidepressant medication or psychotherapy. Patients whose depression is less difficult to treat respond better to TMS than depression which has not responded to many different treatments.
In the UK TMS is currently an experimental procedure used in the context of research, though there are an increasing number of NHS clinics being set up. Newcastle is developing a TMS service now for routine clinical use. A study where an MRI scan is taken first to help in discovering each individual patient’s optimum position of the coil has recently been conducted at sites in the UK. See BRIGhTMIND study for more information (please note that recruitment for this study has stopped). These sites include Newcastle. Results are awaited.