Sky News Australia, on July 12, 2012, reported “Revolution for Parkinson’s Treatment”. The Israel Ministry of Health on July 24, 2012 approved a Brainsway trial for treatment of autism. Google News reported on July 12, 2012, a promising treatment for swallowing problems after stroke.
All these news items have one thing in common; they all report on the potential of noninvasive brain stimulation for treatment of neurological conditions.
Stimulation of the brain ‘from the outside in’ has been around for decades (think about electroconvulsive therapy (ECT) for severe depression). On review of the research on the subject, there is fairly strong evidence that use of the brain stimulation technique, transcranial magnetic stimulation (TMS), improves symptoms of severe depression for patients who do not respond to usual treatment by medication. In 2008, the FDA in the US approved TMS for this purpose. TMS is not approved for use as a therapy for other conditions and is only available as part of a clinical research trial. There are literally hundreds of research trials published and ongoing around the world. A search of PubMed using ‘transcranial stimulation’ in the title or abstract shows 8704 articles; the earliest published in 1956 but most beginning around 1987. In 1991 there were 104 articles published in the field; 314 in 2001 and 969 on 2011. This is clearly a growing area of interest.
By stimulating the neurons within the brain, the researcher can influence the ‘talk’ or connection between neurons and neighbouring neurons; neuronal networks. This activation can ‘turn on’ areas that are not working properly or are perhaps sluggish. The biggest risk of this type of treatment is that turning on groups of neurons could cause an area of overactivity and possibly seizure. There have been a few seizures documented in relation to brain stimulation but this seems to be rare. The other theory is that activation of neurons can help to release neurotrophins that are important for neuroplasticity. In a review by Rothwell in 2012 (Clinical EEG and Neuroscience), he discusses that noninvasive brain stimulation may not be as beneficial on its own but is really a way to ‘prime’ the brain for new learning. When you pair the stimulation with a learning task such as memory training or training of the paralysed hand, the brain stimulation may enhance relearning. That is where there is real potential for recovery. The stimulation is really the potter’s clay and the therapy makes the sculpture.
There are two types of noninvasive brain stimulation techniques in the research literature, transcranial magnetic stimulation and transcranial direct current stimulation. There are subcategories within these two types of stimulation. TMS can be delivered in a continuous wave of stimulation, pulsed (repetitive or rTMS), or in a burst (theta-burst TMS). The other method of stimulation uses electrical rather than magnetic stimulation and can be delivered through transcranial direct current (tDCS) or pulsed current (tPCS). Using direct or pulsed current stimulation, researchers can either activate or silence groups of neurons by choosing to use either the positive or negative electrode over the target area. In most studies, the researchers are only able to stimulate the surface of the brain to a depth of about 1.5cm however some argue that intermittent methods of stimulation may stimulate deeper brain regions.
Wikipedia does a good job of explaining TMS (http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation#FDA_actions). More research findings to follow in future posts!