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Friday, September 28, 2007

8 Effects of TMS on Brain Function but how does TMS work?


Dr Shock is skeptical about the possibilities of Transcranial Magnetic Stimulation (TMS) influencing the neural networks involved with depression. TMS can influence the cortex on the surface and probably a few centimeters beyond. In research TMS has been used to disrupt neural activity experimentally in studies of human cognition but relatively little is known about how TMS works.

Effects of TMS on brain functions:

1.Single burst TMS instead of repetitive TMS applied to the visual cortex interferes with visual imaging (repeated stimulation=rTMS has a longer lasting effect than a sinle burst)

2. Stimulation of the right spot in the motor cortex causes the tumb to twitch (intensity calibration of the TMS stimulus, this is used before repetitive stimulation to other parts of the scalp (rTMS))

3. Low frequency stimulation (1-5 pulses per second) depress brain activity, higher frequency stimulation (25 or more pulses per second) increases excitability.

4. Stimulation of the left prefrontal cortex with rTMS relieves depression in some patients who haven't responded to other antidepressant treatments

5. Low frequency rTMS to the temporoparietal cortex (above the ear) reduces auditory hallucinations in Schizophrenia

6. rTMS treatment on speech areas of the brain can make people name picture at a faster rate

7. rTMS applied to motor regions of the brain facilitates lightening fast movements

8. rTMS applied to the prefrontal cortex compared to sham rTMS enhances solving of analogy puzzles, rTMS might facilitate thinking. (Try rTMS before an exam). rTMS may raise baseline level of neural activity just enough so that neurons don't have to work hard to retrieve memory or problem solving strategies.

What is TMS?
rTMS influences neurons indirectly. It is a non invasive technique to stimulate brain tissue. Anesthesia is not required. Repeated pulses of electric current are sent through a metal wire, which is usually round or figure eight shaped. This electric current generates a perpendicular magnetic field. This magnetic field in return, generates another electric current in nearby material, in this case the current runs through brain tissue just below where the coil is placed on the scalp

How is it applied in Depression?
A depressed patients receives rTMS over the left prefrontal cortex for 20-30 minutes once a day for 2-4 weeks. It is unknowm if this is the right and effective combination of stimulation frequency, intensity, timing, and location.

In a recent article in Science: TMS elicits coupled neural and hemodynamic consequences, a more detailed look on how TMS might affect the neurons is presented.

TMS was applied to the cat visual cortex and the neural and hemodynamic consequences were evaluated.
Short TMS pulse train elicited initial activation (to 1 minute) and prolonged suppression (5-10 minutes). Oxygen concentration and hemoglobin levels were tracked simultaneously with the stimulation and the recordings. Oxygen consumption and hemoglobin are metabolic markers. Both mirrored the pattern of increase in firing (about 1 minute) by the neurons followed by a decrease in firing for several minutes after a stimulation by a TMS pulse train of a few seconds.

Neural activity elicited by flashes of white and black bars on a computer screen which can influence even anesthetized animals, had an altering effect on neural activation by TMS. Neural firing dipped sharply after TMS on the visual cortex and remained suppressed for several minutes during this challenge.
These findings can have important implications for the use of TMS in depressed patients:

The findings have implications for designing TMS therapies, says George. For depression therapy, for example, "we may need people to become sad in the chair while stimulating [them]," George says (Mark George, a psychiatrist at the Medical University of South Carolina in Charleston). "Alternatively, we might have them engage in formal cognitive therapy, thinking positive thoughts." Such considerations are important, he adds, as the Food and Drug Administration is considering approval for daily TMS of the prefrontal cortex to treat depression.

The new findings also suggest why the effects of TMS often vary, says Alvaro Pascual-Leone, a neurologist at Harvard Medical School in Boston. Pascual-Leone suggests that TMS results could be made more consistent by monitoring the physiological state of the brain using electroencephalography or functional magnetic resonance imaging.



Picture used:
The picture at the top of this article is from a website about neurostimulation in all it's forms
Articles used:
Boosting Brain Activity From the Outside In
Laura Helmuth
Science 18 May 2001:
Vol. 292. no. 5520, pp. 1284 - 1286
DOI: 10.1126/science.292.5520.1284

Uncovering the Magic in Magnetic Brain Stimulation
Greg Miller
Science 28 September 2007:
Vol. 317. no. 5846, p. 1846
DOI: 10.1126/science.317.5846.1846a


Transcranial Magnetic Stimulation Elicits Coupled Neural and Hemodynamic Consequences
Elena A. Allen,* Brian N. Pasley,* Thang Duong, Ralph D. Freeman
Science 28 September 2007:
Vol. 317. no. 5846, pp. 1918 - 1921
DOI: 10.1126/science.1146426



6 comments:

Aqua said...

I am so glad I found your website. I've had ECT for my Treatment Resistant Depression. It seemed to help somewhat, but for a short period. I'm thinking of it again, but am a bit concerned after reading this study: http://www.cma.ca/multimedia/staticContent/HTML/N0/l2/jpn/vol-32/issue-4/pdf/pg241.pdf Are you familiar with it? Any comments about it?

I have been diagnosed by my psychiatrist, Chronic MDD and anxiety disorder, but told there is a "bipolarity" to my depression. When I had ECT the inpatient psychiatrist said I had bipolar II. Thus my concern.

I have thought about rTMS, but I am very skeptical as well. It would be nice to know if:

.."For depression therapy, for example, "we may need people to become sad in the chair while stimulating [them]," George says [or] "Alternatively, we might have them engage in formal cognitive therapy, thinking positive thoughts."

...kind of scary to try rTMS with the little info available on the outcomes and such dichotomous ideas about how it should be performed. I'd hate to come out of it more depressed because I thought unhappy thoughts, or vice versa.

Dr. Shock said...

I am familiar with the article you mentioned. The important question is whether patients with bipolar disorder are more at risk for cognitive side-effects of ECT compared to patients with unipolar disorder.But it is unlikely that these findings even if confirmed would change the risk benefit ratio for this effective treatment. That is something to be discussed with your psychiatrist. Let him know your concerns, let him explain why ECT is an option, ask whether there are other options.

As for rTMS I haven't heard or read about patients getting worse from this treatment but negative results do tend to get lost in scientific papers and I've no experience myself with treating depressed patients with rTMS.


I think reading, thinking and discussing these treatments as you do takes courage and perseverance which I greatly admire, regards,

Dr Shock

Herb said...

I am personally aware of several patients who partook of rTMS. As with other treatment options there is no guarantee of an efficacious outcome but unlike ECT from my readings and research the potential side-effects of diminished cognition and memory appear to be absent this therapy.

The several patients I am familiar with did not have any positive outcome from rTMS but then again they also experienced no serious side-effects.

There were several patients who testified at the FDA device panel meeting of experts who testified the rTMS therapy did benefit them. Apparently the evidence supporting any benefits were weak at that time that the panel made no formal decision based upon the evidence presented other than to indicate the evidence was weak.

http://www.vnsdepression.com/pp10-926-articles_10-19-06-FDA-Delays-Meeting-on-Depression-Device.htm

I am very much in agreement with Dr. Shock’s suggestion of discussing additional treatments with one’s attending physician although from my personal years of experiences and research and that which I know today, I would withhold and/or avoid the use of ECT unless a serious mood state was evident such as uncontrolled suicidal ideations.

Hopefully through other aggressive treatment options and/or participation in research studies for some of the newer neuro-modulation therapies such as rTMS the decline into a serious depressive mood state could be alleviated and the need for ECT avoided.

Warmly,
Herb
VNSdepression.com

Anonymous said...

I have spoken with someone who says that TMS literally saved her life-- she was going to kill herself after she lost a child, and TMS helped her to live her life again.

After speaking with her, I believe TMS should definitely be approved by the FDA as a treatment for depression. It may not work in some people, but if it is safe and helps save lives (many of these people are at the point where they may kill themselves due to having no other hope), it is wonderful and should be approved. I thought your write-up on TMS was pretty negative overall-- there are many cases in which people have been saved from their depression by it.

Dr. Shock said...

Your comment does put the use of TMS in perspective. As a scientist I thought that the article was written rather enthusiastic.
As a clinician I think that if all the common treatment options for depression failed every opportunity should be tried to treat depression.
We should keep on searching for the treatments that are the most efficacious for depressed patients, suicidal or not.
TMS is such an option and research will proof it's place in treatment for depression in the future mean while I agree with you that before that no option is to be excluded.
Regards,

Dr Shock

Anonymous said...

Whereas TMS is still an experimental treatment another form of neuromodulation CES [Cranial electrotherapy Stimulation] has an extensive research base with more that 126 human studies [35 double-blind] summarised By Dr. Kirsch in 2002. It is a simple procedure which patients use at home for daily treatments of 20-60 minutes. I have around 50 patients using their own devices at home to treat anxiety, depression,insomnia and pain. Around 80% who test CES find benefit with an average improvement of around 50% - many have treatment-resistant conditions. Research information is available at www.alpha-stim.com Based on my experience I would suggest that this should be the first treatment tried before contemplating more expensive and invasive procedures - its no miracle cure but it helps a lot of people and the side effect burden is low - most of my patients rent a unit for a month and then decide whether to purchase it outright..

Cheers - Steve