rtms introduction

1. TRANSCRANIAL
MAGNETIC STIMULATION
Faten Alzaben PGY5 RESIDENT

2. What is it?
 TMS is a non-invasive method of brain
stimulation in which magnetic fields are used
to induce electric currents in the cerebral
cortex, thereby depolarizing neurons.

3. Early Attempts!

4. Modern Application

5. Even More Modern

6. History
 the idea of using TMS goes back to the early
1900s.
 1985 tony barker and colleagues .
 1984 David Cohen, 1988 Shoogo Ueno :
the idea and realization of the figure-of-eight
coil .

7. Mechanism of action of TMS
 Electrical energy is converted to magnetic
fields ,which are then converted back into
electrical currents in the brain.
 TMS is sometimes called”electrodeless
electrical stimulation”

8. Applications of TMS
 A research tool to study aspects of the human
brain physiology
 Therapeutic application:
 Neurological disorders
 Psychiatric disorders

9. TMS as a research tool
 A research tool to study aspects of the human
brain physiology including motor
function,vision,language and the
pathophysiology of brain disorders
 TMS can excite or inhibit the brain allowing
functional mapping of cortical regions and
creation of transient functional lesions.

10. Examples:
 rTMS over the occipital lobe impaired
detection of visual stimuli
 rTMS delivered to discrete areas in the
language-dominant hemisphere can disrupt
speech.

11. Therapeutic Application in
Neurological Disorders

12. Movement disorders:
 Therapeutic applications of TMS in movement disorders are
preliminary.
 Fast rTMS of the motor cortex has been reported to
improve performance on several motor measures in
Parkinson disease.
 a recent meta-analysis included 12 studies and
concludes that the overall literature does show a positive
effect of r TMS on Parkinson motor function.
 Slow rTMS has been reported to improve dystonia.
George, linsbey ,and sackiem
Fregni et al. 2005

13. Neuro-rehabilitation
 TMS to evaluate the functional properties of
the motor cortex after lesions like stroke is of
special interest in the field of
neurorehabilitation.
 Brain stimulation have been proposed to
enhance motor function when combined with
conventional neurorehabilitative interventions
after stroke

14. Chronic Pain
(rTMS) of the cortex induces analgesic effects in
focal chronic pain syndromes.

15. Therapeutic Application in
Psychiatric Disorders

16. Mood Disorders
 Several studies demonstrated that repetitive
transcranial magnetic stimulation (rTMS) is an
efficacious treatment for treatment-resistant
major depression.
 its efficacy has often been shown to be
modest, compared with sham stimulation.

17. Mechanisms of rTMS-Induced
Antidepressant Response
 evidence suggests that MDD is most
commonly associated with hypoexcitability over
the left prefrontal cortex and hyperexcitability
over the right prefrontal cortex

18. Evidence in support left prefrontal
hypoexcitablity in depression:
 Brain injury:
 patients with left-sided strokes (hypoexcitability)
experience depression
 Patients with right-sided strokes experience manic
symptoms
 Imaging studies demonstrated that MDD
may involve lower activity in the left DPLFC
and higher activity in the right DPLFC.

19.  rTMS treatment in MDD has often been
shown to be associated with a normalization
of hypoexcitability over the left prefrontal
cortex and normalization of hyperexcitability
over the right hemisphere.

20.  Studies have demonstrated that when 10 Hz
rTMS is applied to the right DLPFC ,
dysphoric symptoms occur.

21. Review of Studies of rTMS in
Depression
 Studies in the review were summarized into 5 broad categories:
 1- first-generation studies that have evaluated the efficacy of 10
rTMS sessions (that is, 2 weeks) for TRD.
 2-second-generation studies that have evaluated the efficacy of
rTMS for more than 10 rTMS sessions.
 3-third-generation studies that evaluate the efficacy of rTMS using
several novel treatment approaches (for example, bilateral rTMS).
 4- metaanalytic studies of rTMS for TRD.
 5-future studies proposing novel methods to optimize the efficacy of
rTMS for TRD.
The Canadian Journal of Psychiatry, Vol 53, No 9, September 2008

22. First-Generation Studies
 rTMS studies applied at high frequencies (10 to
20 Hz) over the left prefrontal cortex have
demonstrated efficacy in the treatment of
depression.
 Other studies also demonstrated right low-
frequency rTMS to be useful in depression.
 Other first-generation studies were equivocal or
showed lack of efficacy.
 Other studies have also reported negligible
results.

23.  Explanations :
1- most patients included in these studies were
treatment resistant.
2- stimulation parameters including frequency,
intensity, and duration vary from study to study.
3- concomitant use of medications .
4- no consistent method for precisely localizing the
prefrontal cortex.

24. Second-Generation Studies
 20 or more treatments.
 The results demonstrate that both HFL- and
LFR-rTMS have substantial therapeutic
efficacy.

25. Third-Generation Studies
 bilateral rTMS.
 The studies showed no difference between
the groups.
 Limitations of these studies:
 First, bilateral rTMS was not compared with
unilateraland sham rTMS in a sufficiently large
sample of subject.
 none of the studies were conducted for longer
than 10 days .
 none used more than 300 LFR-rTMS pulses.

26. Metaanalyses of rTMS in MDD
 There have been at least 8 meta -analyses
evaluating the anti-depressant effects of left
DLPFC rTMS. All but one have shown greater
antidepressant effects at 2 weeks of HFL-
rTMS, compared with sham.

27. Limitations of Current rTMS
Trials in MDD
Factors underlie the relative modest therapeutic
efficacy of rTMS studies conducted in MDD:
1- most of these studies involved left-sided
treatment alone to the DLPFC.
2- suboptimal methods were used to target the
DLPFC .
3-treatment durations were typically short (that is, 2
to 4 weeks).
4- stimulation intensity might have been
insufficient by
not taking into consideration coil-to-cortex
distance

28. Anxiety Disorders
 obsessive-compulsive disorder
 posttraumatic stress disorder
 panic disorder

29. Schizophrenia
 reduced auditory hallucinations
 reduced anxiety

30. Difference Between TMS and
ECT
 TMS:
 does not require general anaesthesia
 easy to administer in alert and wake subjects
under medical supervision
 no cognitive deficits reported at this point.
 Does not involve induction of seizures

31. Adverse Effects of rTMS
 Risk of inducing seizures (in patients with a hx
or family hx of seizures).current safety
protocols adjust the amount of stimulation in
relation to the motor threshold of the individual.
 Muscle tension headache .
 Short term changes in hearing threshold
related to the noise generated.
 Cognitive changes only during stimulation

32. Thank You !