One of the risk factors when using Transcranial Magnetic Stimulation is a history of severe head trauma, and it is even included by Rossi et al (2009) in their proposed screening questionnaire (A Consensus Statement from the International Workshop on “Present and Future of TMS: Safety and Ethical Guidelines”, Siena, March 7–9, 2008). However, there are many studies examining mTBIs using TMS, how can this be the case? Is it because single pulse TMS is used, as opposed to repetitive TMS?
Dear Thomas! Thank you. You raised the issue of the day.
There are specific recommendations for the purpose of instrumental diagnostic procedures. You know about this. Unfortunately, some clinicians are not aware of these recommendations. It is particularly important to comply with such recommendations in the application of modern diagnostic devices, such as transcranial magnetic stimulation. Developed specific indications for the use of the TMS with brain injury. This avoids the negative side effects.
Vladimir
Thomas
Basically, you should not use TMS in patients with history of brain injury
in your research lab if you cannot provide qualified medical assistance -
take a look at the table 7 from Rossi et al.'s guidelines. Many rTMS and
tDCS studies have been conducted even on severe TBI but they are usually
carried out in hospital settings. That is the first condition. The second
is informed consent from your patient and ethical committee agreement. The
aim of your research is a crucial issue. If the results may help find a
new treatment for individuals with brain injury the choice of a clinical
population is justified. If it is just for fun, well, you can always ask
your healthy colleagues to participate in your experiment... Anyway, you
need to assume that there is ALWAYS some risk.
Good luck
Marcin
It's also important to note that TBI is not a single entity - while the seizure risk is elevated in some subtypes of TBI, it is not significantly elevated in patients with diffuse axonal injury (the most common type of TBI).
It's also useful to note that the seizure risk from rTMS is quite low at baseline. As such, if you, your subject, and your IRB are willing to accept that risk because you think that it is outweighed by the benefit, you could certainly study it.
Just because there is a risk associated with something doesn't mean that you can't study it further.
Dear Thomas,
My lab has used single-pulse TMS on both healthy volunteers and stroke survivors, who have a one-sided lesioned hemisphere. In order to assess whether the participant is safe to use TMS, we go through a safety questionnaire that contains all of the possible contraindications of it. This includes whether the participant has had any previous adverse effects from TMS, a history of epilepsy or seizures, brain surgery, any metal implants or devices on the head or face.
With that being said, on the day of the TMS testing, we make sure that the participant is comfortable and well to go. In my experience, some participants are less sensitive to the pulse and even fall asleep during the procedure; some other participants are more sensitive to the pulse, and so we would lower the pulse to a limit that the participant is comfortable with. Other things also matter, such as whether the participant has had a good rest the night before, and has eaten a good breakfast in the morning.
Like others had answered, there's always a risk of using the TMS, and we go through to explain these risks to the participants in a consent form.
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