The first TMS device was invented by Dr. Anthony Barker in Sheffield, England in 1985 and it was intended solely for research purposes. It was originally used as a brain mapping tool where it has a time resolution ranging from milliseconds up to about an hour and a spatial resolution down to the level of the cell column or cerebral cell layer.
One thing that TMS is especially good at is stimulating the motor cortex, which controls voluntary movement, so a lot of the early research was focused on movement disorders. By the mid 1990s, several investigators had made the same interesting observation: patients with Parkinson's disease, who were being studied with TMS, reported significant improvement in mood.
At first the papers just trickled in. Then they began pouring in from all over the world. Before long many researchers agreed that TMS was probably an effective treatment for depression, The question was: how effective? Different researchers were using very different protocols at the time which made it hard to compare one study to another. But there was another question too: is it safe?
It seemed to be pretty safe. The only thing that anybody complained about was minor scalp irritation at the stimulus site and this usually went away after a few treatments. But every once in a while, somebody had a seizure. It didn't happen very often, but the fact that it happened at all was bad news, and clearly there were still some questions to be answered.
- How strong should the magnetic pulses be?
- How rapidly should they be delivered?
- For how long?
- And to what part of the brain?
Eventually all of these questions were answered. Guidelines were published in 1998 and since then the risk of having a seizure from TMS has been reduced even further.
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