TMS involves the application of a dynamic magnetic field to the scalp in order to induce electrical activity in the underlying cortex of the brain. A coil of wire, encased in plastic, is held to the head. A rapidly changing current flows in its windings. This produces a magnetic field. The magnetic field passes through the skin and skull. This induces current in the brain. The current induced in the structure of the brain activates nearby nerve cells in much the same way as currents applied directly to the cortical surface.
Some studies support the potential of TMS as a treatment for severe depression, whilst others have found little or no benefit. Although the National Institute for Health and Clinical Excellence (NICE) guidelines (2007) were uncertain about the effectiveness of TMS, they recommended that further research is undertaken to identify the patient selection criteria, the best use of the procedure, and the duration of treatment effect.
The aim of this study was to examine the effectiveness of TMS for patients suffering from severe depression.
In 2003, the 5 Boroughs Partnership NHS Trust established the first UK clinical TMS service. Patients meeting the referral criteria received at least 120% of the motor threshold. The Motor Threshold is the minimum dosage of stimuli required to stimulate the motor cortex.
All the clinical symptoms of depression and anxiety were measured, using established rating scales, before treatment and after every five treatments. A cognitive examination was carried out before the study began and again at the end of treatment.
In total there were 135 referrals to the TMS service. Assessments were completed on 115 of them. 17 referrals were declined, as they were inappropriate.
Of the remaining 98 patients, 76 received full treatment and 22 could not complete the course of treatment. 49 patients (50%) showed a 50% reduction in symptoms of depression. Of those who responded to TMS, 66% were female and 33% male.
The researchers conclude that TMS is effective in treating severe depression. Many technical details, such as the site of stimulation, stimulus frequency, the total number of stimuli and the duration of the treatment, need to be further refined.
Further studies should be undertaken to validate the treatment effect and duration and the durability of the results, and also to further define the best stimulation parameters.
Repetitive TMS clearly has physiological effects on the brain, an observation that is remarkable in itself. It may well be that the technology has potential therapeutic effects in a range of psychiatric disorders that involve brain neurons.
It is important, say the researchers, that the challenges of this technology are overcome, in order to pursue the potential clinical benefits of TMS for patients with mental health problems.
Source: Royal College of Psychiatrists (Press Release)
References:
Royal College of Psychiatrists’ Annual Meeting, Imperial College, London, 1 - 4 July 2008
