Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation
Published with the kind permission of Professor Vincent Walsh

Transcranial Magnetic Stimulation (TMS) is a method of stimulating neurons in the brain using weak electrical currents. Rapidly changing magnetic fields produce ‘eddy currents’ that trigger brain activity. This allows researchers to map the functioning areas of the brain and the connections between them. Transcranial magnetic stimulation is primarily used to measure brain activity and help diagnose problems. However, there have been recent moves to use TMS therapy as a treatment for a range of neurological conditions. The therapy usesRepetitive Transcranial Magnetic Stimulation (rTMS). This is because repeating the magnetic pulses creates longer-lasting changes in brain function.

During the treatment, the researcher places electrical coils on the head. In general, there is little or no sensation. In most cases, the patient does not notice anything unusual, except the changes in his or her behaviour the researchers are creating. For example, the researcher can choose to shut down your ability to speak or to perform a task. The only pain associated with TMS therapy seems to be an occasional irritation of the scalp from the coils.

Transcranial magnetic stimulation is improving all the time. Experts have recently introduced ‘deep TMS’, which means they are no longer limited to the areas of the brain nearest the skull.

 

transcranial magnetic 2

Direct Current Stimulation Published with the kind permission of Professor Vincent Walsh

 

 

 

 

 

 

  • Possible benefits of Transcranial Magnetic Stimulation for stroke

    A number of studies have used rTMS to improve hand movement and function in adult and child stroke survivors.1 Most of these studies show measurable benefits and lasting improvements in mobility after the treatment. One study concluded that people who have suffered a severe stroke can make new mental connections that help them to learn more effectively through repetitive exercises:

    ‘High-frequency rTMS of the affected motor cortex can facilitate practice-dependent plasticity and improve the motor learning performance in chronic stroke victims.’ 2

    These findings are supported by other trials. For example, in 2008, 10 children with stroke were treated with TMS. After the treatment, the children’s hand function had improved. 3 Again in 2008, researchers examined 12 adults who had suffered a stroke four to five years previously. All had moderate to severe difficulties with hand and arm movement. The participants were given a single session of rTMS, which lasted 20 minutes. Researchers found the treatment to be safe and ‘modest improvements were seen, for example, in grip strength, range of motion, and pegboard performance, up to 1 week after rTMS.’ 4

    A recent study combined Theta Burst Stimulation (a particular pattern of rTSM) with training after subcortical stroke. For the study, 10 patients with chronic subcortical stroke and upper-limb impairment were recruited. The patients were given either genuine rTMS or sham rTMS. The sham rTMS was delivered with a sham coil. It found that the real treatment was beneficial for gripping and lifting movements with the affected hand:

    ‘Training after real TBS improved paretic-hand grip-lift kinetics, whereas training after sham TBS resulted in deterioration of grip-lift. […] Generally, TBS and training led to task-specific improvements in grip-lift.‘5

    Another study used Transcranial Direct Current Stimulation (tDCS) to decrease the amount of activity in the unaffected side of the brain of a stroke patient. This caused the damaged side of the brain to improve. As a result, the patient had increased movement (motor function).6 There is also evidence that it can help to improve learning and memory function, both in healthy people and in those with brain injury.7

    In 2008, Anwen Evans concluded his review of TMS and stroke with these words:

    ‘Transcranial Magnetic Stimulation has an important role to play in the fight against Stroke and its consequences, whether as a prognostic technique, or as a rehabilitative method. Further research is needed to decide in which area TMS may be best utilised, but the research undertaken so far is very encouraging.’8

    Many of the problems stroke survivors experience are due to broken connections between neurons. This can cause symptoms such as paralysis, aphasia and shaking. Repetitive Transcranial Magnetic Stimulation (rTMS) can stimulate two neurons at the same time in order to re-build a connection. This treatment can also prevent (inhibit) activity in one area of the brain in order to stimulate activity in a different area.

  • Arguments against using Transcranial Magnetic Stimulation for stroke

    One argument against accepting the results of TMS studies is the fact that, in general, they cannot use a placebocontrol group. In most research, at least two groups of people are studied: one is given the real treatment and the other is given a dummy treatment. This allows researchers to see if the treatment is really working, or if the patient’s belief or wish to get better is influencing the results. In TMS, the patient is aware when the equipment is on. This makes it difficult to measure results accurately because researchers cannot rule out the effect of the patient’s belief that the treatment is working.

    One risk associated with TMS and rTMS is the danger that using electrical currents could produce a seizure. The risk increases if the patient suffers from epilepsy.9

    There have not been many large-scale, high-quality trials of this treatment. Many of the studies we have discussed concluded with a call for more extensive clinical trials.

  • Case histories

    This short article describes how TMS helped a group of stroke survivors to improve by up to 50% in some areas.  ‘Magnetic stimulation may improve stroke recovery‘ by Robin Thompson. Source: EurekAlert

  • Notes and references
    1. ‘Therapeutic trial of repetitive transcranial magnetic stimulation after acute ischemic stroke’ by Khedr EM, Ahmed MA, Fathy N, Rothwell JC. In Neurology, 2005 Aug 9;65(3):353-4.
    2. ‘Repetitive transcranial magnetic stimulation-induced corticomotor excitability and associated motor skill acquisition in chronic stroke’ by Kim YH, You SH, Ko MH, et al. In Department of Physical Therapy, Graduate School of Rehabilitation Therapy, Yonsei University, Wonju City, Kangwon-do, Republic of Korea.
    3. Contralesional repetitive transcranial magnetic stimulation for chronic hemiparesis in subcortical paediatric stroke: a randomised trial’ by Adam Kirton, Robert Chen MBBChir, et al. In The Lancet Neurology, Volume 7, Issue 6, pp 507 – 513, June 2008
    4. Safety and behavioural effects of high-frequency repetitive transcranial magnetic stimulation in stroke’ by Yozbatiran N, Alonso-Alonso M, See J, Demirtas-Tatlidede A, Luu D, Motiwala RR, Pascual-Leone A, Cramer SC. In Stroke, 2009 Jan;40(1):309-12. Epub 2008 Oct 9.
    5. Ackerley SJ, Stinear CM, Barber PA, Byblow WD, ‘Combining Theta Burst Stimulation With Training After Subcortical Stroke’. In Stroke 41(7), 2010, pp 1568-1572, p. 1568
    6. ‘Transcranial direct current stimulation of the unaffected hemisphere in stroke patients’ by Fregni, Felipe, Boggio, Paulo S., Mansur, et al. In Neuroreport. 16(14):1551-1555, September 28, 2005.
    7. ‘Consensus: Can tDCS and TMS enhance motor learning and memory formation?’ by Janine Reis, Edwin Robertson, et al. In Brain Stimulation. 2008 October; 1(4): 363–369.
    8. ‘Transcranial Magnetic Stimulation and Stroke: A Review’ by Anwen Evans. In NeuroImage, 30 (3):857-870, 2006
    9. This article states:’Repetitive transcranial magnetic stimulation (rTMS) is emerging as a new therapeutic tool in epilepsy, where it can be used to suppress seizures or treat comorbid conditions such as mood disorder. However, as rTMS  carries a risk of inducing seizures among other adverse events, its safety and tolerability in the population with epilepsy warrant distinct consideration, as this group is especially seizure-prone.’In Epilepsy Behav. 2007 Jun;10(4):521-8. Epub  2007 May 9.’Safety and tolerability of repetitive transcranial magnetic stimulation in patients with epilepsy: a review of the literature.’ Bea EH, Schrader LM et al., Department of Neurology, Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA.

Aviva Cohen is the author and CEO of Neuro Hero