obsessive - compulsive disorder ( ocd ) is a highly disablitating psychiatric disorder characterized by obsessions and compulsions .
obsessions are egodystonic , unwanted thoughts , images , or impulses that repeatedly enter one s mind .
compulsions are repetitive , time - consuming behaviors or mental acts often performed to neutralize the anxiety provoked by obsessions .
the prevalence of ocd in the general population is estimated at 1% to 3% , and the disorder is associated with impaired functioning and decreased quality of life [ 2 , 3 ] . the general treatment of ocd is a serotonin reuptake inhibitor at an adequate dose , cognitive - behavioral therapy , or a combination of the two .
however , up to 40% of patients fail to respond satisfactorily to these generally adequate treatment options , and 10% can not be helped at all [ 1 , 4 ] . with use of repetitive transcranial magnetic stimulation ( rtms ) ,
it has become possible to modulate local neural activity by inducing a depolarizing magnetic field pulse . because ocd may be related to increased neural activity in prefrontal subcortical circuits , the inhibitory effect of rtms was hypothesized to be beneficial in ocd treatment . in 1997 , greenberg et al .  
earlier , rtms had been shown to have a positive effect on mood disorders with stimulation of the prefrontal cortex .
greenberg et al .   hypothesized that inhibition of the prefrontal activity with rtms might reduce obsessive - compulsive symptoms .
they applied rtms ( 80% motor threshold , 20  hz for 2  s / min ) for 20  min to 12 patients with ocd and found significantly decreased compulsive urges for 8  h after stimulation .
since then , rtms has been investigated in ocd , targeting several brain areas within the corticostriatal network . in this article , the mechanism of action is discussed first , then the efficacy and side effects of rtms at various brain targets , and finally implications for the future .
in the early-1980s , the transcranial magnetic stimulation ( tms ) device was developed by barker and colleagues .
it uses a strong pulse of electrical current that is sent through a coil to induce a magnetic field pulse in the area under the coil .
this pulse has the capacity to depolarize superficial local neurons . to create a longer lasting effect of the depolarized neurons , application of rtms
is needed . the magnitude and direction of rtms - induced neuronal modulation depend on extrinsic factors such as motor threshold , frequency , and total number of stimuli , and intrinsic factors such as the functional state of the cortex .
for example , it appears that low - frequency rtms ( 05  hz ) results in decreased neural excitability and regional cerebral blood flow , as opposed to high - frequency rtms ( 520  hz ) , which increases both .
because knowledge of involvement of specific brain circuits in ocd is advancing , rtms has been applied to several brain targets ( table  1 ) .
the rationale for the first rtms studies in ocd was based on functional neuroimaging studies of ocd that demonstrated abnormalities in the orbitofrontal subcortical circuits , especially in the orbital frontal gyri and medial caudate nuclei .
this circuitry may be manipulated with rtms by 1 ) stimulation of the dorsolateral prefrontal cortex ( dlpfc ) , 2 ) inhibition of the orbitofrontal cortex ( ofc ) directly , or 3 ) inhibition of the supplementary motor area ( sma ) .
the sma was chosen as a useful target for rtms because it has extensive connections with regions implicated in cognitive processes and motor control [ 14 , 15 ] . 

table  1summary of studies of repetitive transcranial magnetic stimulation in treatment of obsessive - compulsive disorderstudy ( year)targetndiagnosismedication continuationinterventiontimemean score ( sd ) on y - bocs pre - rtmsmean score ( sd ) on y - bocs post - rtmsmean score on mood scale pre - rtmsmean score on mood scale post - rtmsinterventiongreenberg et al .  
treatment)20 hz/2 s / min ( 80% of motor threshold)1 session of 20 min ; measurement after 8 h  compulsions decreased right pfc ( p  =  0.02 ) ( left pfc p  =  0.05)no significant mood improvementcontrolmidoccipital12ocd20 hz/2 s / min ( 80% of motor threshold)1 session of 20 min ; measurement after 8 h  compulsions decreased ( midoccipital p  =  0.07)no significant mood improvementinterventionsachdev et al .  
( 2001)right pfc6treatment - resistant ocdyes , n  =  10 ( stable sri , benzodiazepine , neuroleptic treatment)10 hz ( 110% motor threshold)10 sessions of 2.5 min in 2 week ; measurement 4 week after last session27.2 ( 9.0)12.0 ( 3.9)23.2 ( 12.5 ) on bdi11.6 ( 14.6 ) on bdicontrolleft pfc6treatment - resistant ocd10 hz ( 110% motor threshold)10 sessions of 2.5 min in 2 week ; measurement 4 week after last session22.5 ( 6.3)16.5 ( 8.3)19.7 ( 12.5 ) on bdi10.8 ( 7.9 ) on bdiinterventionalonso et al .  
( 2001)right dlpfc10ocdyes , n  =  7 ( stable sri , tca treatment)1 hz ( 110% of motor threshold)18 sessions of 20 min in 10 week ; measurement after 10 week24.0 ( 5.3)20.6 ( 9.1)11.1 ( 5.1 ) on ham - d10.8 ( 4.8 ) on ham - dcontrolright dlpfc8ocdyes , n  =  6 ( stable sri , tca treatment)sham condition18 sessions of 20 min in 10 week ; measurement after 10 week25.6 ( 6.1)25.3 ( 8.3)11.7 ( 2.7 ) on ham - d12.0 ( 3.0 ) on ham - dinterventionmantovani et al .   ( 2006)sma10ocd / tsyes , n  =  10 ( stable sri , benzodiazepine , neuroleptic treatment)1 hz ( 100% of motor threshold)10 sessions of 20 min in 2 week ; measurement 2 week after last stimulation36.4 ( 7.5)26.0 ( 10.5)20.7 ( 11.4 ) on ham - d10.8 ( 10.7 ) on ham - dcontrolinterventionprasko et al .  
( 2006)left dlpfc15sri - resistant ocdyes , n  =  15 ( stable sri treatment)1 hz ( 110% of motor threshold)10 sessions of 30 min in 2 week ; measurement 2 week after last stimulation29.8 ( 5.8)21.4 ( 9.2)controlleft dlpfc15sri - resistant ocdyes , n  =  15 ( stable sri treatment)sham condition10 sessions of 30 min in 2 week ; measurement 2 week after last stimulation23.4 ( 5.0)16.9 ( 5.9)interventionsachdev et al .  
( 2007)left dlpfc10ocdyes , n  =  9 ( unknown treatment)10 hz ( 110% of motor threshold)10 sessions of 2.5 min in 2 week ; measurement directly after last stimulation26.020.0symptoms improved over time but no difference between groupscontrolleft dlpfc8ocdyes , n  =  4 ( unknown treatment)sham condition10 sessions of 2.5 min in 2 week ; measurement directly after last stimulation24.019.0symptoms improved over time but no difference between groupsinterventionruffini et al .  
( 2009)left ofc16drug - resistant ocdyes , n  =  23 ( stable sri , neuroleptic , antiepileptic , benzodiazepine treatment)1 hz ( 80% of motor threshold)15 sessions of 10 min in 3 week ; measurement 12 week after last session32.1 ( 6.0)27.3 ( 9.4)no mood improvement over timecontrolleft ofc7drug - resistant ocdsham condition15 sessions of 10 min in 3 week ; measurement 12 week after last session31.4 ( 6.9)29.6 ( 6.7)no mood improvement over timeinterventionkang et al .
[ 17 ] ( 2009)right dlpfc and sma10treatment - resistant ocdyes , n  =  10 ( stable sri , benzodiazepine treatment)1 hz ( 110% of motor threshold)14 sessions of 10 min in 2 week ; measurement 2 week after last session26.5 ( 5.6)23.6 ( 7.4)18.1 ( 6.6 ) on bdi17.2 ( 10.9 ) on bdicontrolright dlpfc and sma10treatment - resistant ocdyes , n  =  10 ( stable sri , benzodiazepine treatment)sham condition14 sessions of 10 min in 2 week ; measurement 2 week after last session26.3 ( 4.1)22.9 ( 6.2)16.7 ( 10.0 ) on bdi15.8 ( 14.4 ) on bdiinterventionmantovani et al .
[ 18 ] ( 2010)sma9ocdyes , n  =  13 ( stable sri treatment)1 hz ( 100% of motor threshold)20 sessions of 20 min in 4 week ; measurement directly after last stimulation26.0 ( 5.4)19.4 ( 5.6)15.3 ( 10.6 ) on ham - d12.1 ( 11.4 ) on ham - dcontrolsma9ocdsham condition20 sessions of 20 min in 4 week ; measurement directly after last stimulation26.7 ( 5.5)23.5 ( 9.0)14.8 ( 6.9 ) on ham - d14.1 ( 8.8 ) on ham - dinterventionsarkhel et al .  
( 2010)right dlpfc21ocdyes , n  =  21 ( tca , sri treatment)10 hz ( 110% of motor threshold)10 sessions in 2 week ; measurement 2 week after last session25.7 ( 3.9)change in score , 5.0 ( 2.3)12.5 ( 2.2 ) on ham - dchange in score , 3.8 ( 1.6 ) on ham - dcontrolright dlpfc21ocdyes , n  =  21 ( tca , sri treatment)sham condition10 sessions in 2 week ; measurement 2 week after last session23.6 ( 3.7)change in score , 4.2 ( 1.8)12.1 ( 2.7 ) on ham - dchange in score , 3.2 ( 1.0 ) on ham - dsame 12 individuals as investigated in the intervention groupbdi beck depression inventory , dlpfc dorsolateral prefrontal cortex , ham - d hamilton depression rating scale , ocd obsessive - compulsive disorder , ofc orbitofrontal cortex , pfc prefrontal cortex , rtms repetitive transcranial magnetic stimulation , sma supplementary motor area , sri serotonin reuptake inhibitor , tca tricyclic antidepressant , ts tourette s syndrome , y - bocs yale - brown obsessive compulsive scale summary of studies of repetitive transcranial magnetic stimulation in treatment of obsessive - compulsive disorder same 12 individuals as investigated in the intervention group bdi beck depression inventory , dlpfc dorsolateral prefrontal cortex , ham - d hamilton depression rating scale , ocd obsessive - compulsive disorder , ofc orbitofrontal cortex , pfc prefrontal cortex , rtms repetitive transcranial magnetic stimulation , sma supplementary motor area , sri serotonin reuptake inhibitor , tca tricyclic antidepressant , ts tourette s syndrome , y - bocs yale - brown obsessive compulsive scale
a total of 110 ocd patients in 10 studies have been treated with rtms , targeting the dlpfc , the ofc , or the sma .
four studies investigated the efficacy of rtms in ocd in a double - blind , randomized , sham - controlled design [ 12 , 16 , 18 , 19 ] ; three studies in a sham - controlled design , although not double - blind [ 13 , 17 , 20 ] ; and three case studies in an open fashion [ 7 , 14 , 21 ] .
the dlpfc has been the most investigated target for rtms in ocd . in 1997 , greenberg et al .  
treated 12 ocd patients with rtms to the right dlpfc , the left dlpfc , and lastly the midoccipital cortex as a control condition .
rtms was randomly applied to these targets in an open fashion on separate days , at 80% threshold , 20  hz for 2  s / min for 20  min .
compulsions , as measured by the yale - brown obsessive compulsive scale ( y - bocs ) , decreased significantly with 34.8% immediately after right dlpfc stimulation ( p  <  0.01 ) and remained significant 8  h afterward ( p  <  0.02 ) , whereas obsessions did not decrease significantly .
depressive symptoms decreased significantly as well , although the effect did not last longer than 8  h. compulsions decreased instantly with 26.8% ( p  < 
0.03 ) following left dlpfc stimulation , but similar to depressive symptoms , they returned after 8  h. midoccipital stimulation increased compulsions , as measured by the y - bocs ( nonsignificantly ) ( p  =  0.07 ) . in 2001 , sachdev et al .   tried to replicate this study in 12 patients with treatment - resistant ocd .
( n  =  6 ) and left ( n  =  6 ) dlpfc stimulation was applied in an open fashion at 10  hz , 100% motor threshold for 10 sessions of 2.5  min . at 4  weeks of follow - up , rtms led to a mean decrease on the y - bocs of 57% for right dlpfc and 27% for left dlpfc .
all 12 individuals were analyzed together , as there were no differences on any of the parameters measured , and showed a significant decrease of 42% on the y - bocs at 1-month follow - up ( p  =  0.003 ) .
however , after corrections for depression scores on the montgomery - asberg depression rating scale , the significance disappeared ( p  =  0.06 ) . in the same year , the first randomized , sham - controlled , double - blind rtms ocd trial was completed .
alonso et al .   randomly assigned 18 patients with ocd to real rtms ( n  =  10 ) or sham rtms ( n  =  8) at the right dlpfc .
the rtms lasted 20  min at 1  hz for both conditions , but the motor threshold was 110% for real rtms and 20% for sham rtms .
this study failed to find significant improvement on the y - bocs or hamilton depression rating scale ( ham - d ) after 18 sessions . in 2006 , this randomized , sham - controlled , double - blind design was repeated stimulating the left instead of the right dlpfc in 30 treatment - resistant ocd patients .
patients were given 10 daily sessions of sham or real rtms ( 1  hz , 110% motor threshold ) in addition to ongoing serotonin reuptake inhibitor treatment .
after 2  weeks of follow - up , obsessive - compulsive symptoms improved , with mean y - bocs reductions of 28% , but no differences between sham and real rtms were observed .
the authors concluded that rtms did not result in an effect on ocd by stimulating the left dlpfc .
similarly , in a study by sachdev et al . , high - frequency ( 10  hz , 110% motor threshold ) rtms of the left dlpfc yielded significant y - bocs decreases ( 6.0 points , 23.1% ) over 2  weeks in 10 ocd patients , but the effects were similar after sham rtms in 8 patients ( 5.0 points , 20.4% ) . finally , in an indian sham - controlled study , active rtms at 10  hz , 110% motor threshold ( n  =  21 ) and sham rtms ( n  =  21 ) of the right dlpfc elicited similar improvement in obsessions and compulsions 2  weeks after the 10th session . the y - bocs reduction for active rtms was 5.0 points ( 19.5% ) , and 4.2 points ( 17.7% ) for sham rtms .
interestingly , depressive scores , as measured by the ham - d , were reduced significantly over time in the real rtms group compared with the sham rtms group ( p  >  0.04 ) .
a total of 76.2% of those receiving real rtms were partial responders ( 25% reduction in ham - d scores from baseline ) , compared with 66.7% in the sham group .
the authors concluded that right dlpfc rtms has no effect on ocd but is modestly effective in the treatment of comorbid depressive symptoms . in conclusion , in open - label studies , high - frequency rtms of the right and/or left dlpfc appears to be effective in reducing obsessive - compulsive symptoms .
however , this could not be replicated in double - blind , sham - controlled studies . in those studies , neither low nor high rtms and neither rtms to the left nor to
ruffini and colleagues   examined the ofc as a new target for rtms in drug - resistant ocd patients .
the participants received 10  min of 1-hz rtms at 80% motor threshold for 15 sessions to the left ofc ; however , the coil was placed parallel ( active , n  =  16 ) or perpendicular ( sham , n  =  7 ) to the scalp .
they found significant reduction of y - bocs scores comparing active versus sham treatment for 10  weeks after the end of rtms ( p  <  0.02 ) , with loss of significance after 12  weeks ( p  <  0.06 ) .
y - bocs reduction was 19.7% immediately after rtms and 14.7% after 12  weeks of follow - up , but only 6.7% and 5.7% , respectively , for the sham condition .
there was also a benefit in terms of depressive and anxiety symptoms , but not at a significant level in the two groups .
similar to findings for dlpfc rtms , this study suggests that low - frequency rtms of the ofc may only acutely improve obsessive - compulsive symptoms .
two groups investigated the efficacy of low rtms to the sma in addition to ongoing pharmacotherapy . in 2006 , mantovani et al .  
conducted an open - label study of 10 patients with ocd , tourette s syndrome , or both .
individuals were treated with active rtms to the sma for 10 daily sessions at 1  hz , 100% motor threshold .
after 2  weeks of daily rtms , the y - bocs reduction ( 28.6% ) and ham - d reduction ( 47.8% ) were both significant , and they remained stable after 3  months follow - up in the ocd as well as in the ocd / tourette s syndrome group . in 2010 ,
the same group examined rtms ( at 1  hz and 100% motor threshold ) to the sma bilaterally in a randomized , sham - controlled , double - blind design . after 4  weeks of stimulation , the y - bocs decreased significantly ( p  <  0.001 ) in the active group ( 6 points , 25.4% ) and the sham group ( 3.2 points , 12.0% ) without significant differences between the two treatment conditions .
finally , an open , sham - controlled study investigated the possible therapeutic effects and safety of sequentially combined low - frequency ( 1  hz , 110% threshold ) rtms to the right dlpfc and the sma in 10 patients with treatment - resistant ocd .
similar improvements in obsessive - compulsive and depressive symptoms were observed for sham and real rtms at 2  weeks after the last of 14 sessions .
the y - bocs reductions were 2.9 points ( 10.9% ) and 3.4 points ( 12.9% ) for real and sham rtms , respectively .
rtms was a safe method , and there was no significant change in cognitive functioning after stimulation .
similar to dlpfc and ofc stimulation , rtms to the sma was a safe method to immediately improve obsessive - compulsive symptoms ; however , improvement did not linger on over time . in conclusion ,
efficacy of low- and high - frequency rtms to the left or right dlpfc , the ofc , or the sma has been investigated in a total of 110 obsessive - compulsive patients over the past decade .
although open studies have initially demonstrated beneficial effects of rtms on obsessive - compulsive and depressive symptoms during the first hours after stimulation , these effects disappeared during follow - up and , more importantly , rtms did not show any advantages over sham stimulation in double - blind , sham - controlled studies .
the dlpfc has been the most investigated target for rtms in ocd . in 1997 , greenberg et al .  
treated 12 ocd patients with rtms to the right dlpfc , the left dlpfc , and lastly the midoccipital cortex as a control condition .
rtms was randomly applied to these targets in an open fashion on separate days , at 80% threshold , 20  hz for 2  s / min for 20  min .
compulsions , as measured by the yale - brown obsessive compulsive scale ( y - bocs ) , decreased significantly with 34.8% immediately after right dlpfc stimulation ( p  <  0.01 ) and remained significant 8  h afterward ( p  <  0.02 ) , whereas obsessions did not decrease significantly .
depressive symptoms decreased significantly as well , although the effect did not last longer than 8  h. compulsions decreased instantly with 26.8% ( p  < 
0.03 ) following left dlpfc stimulation , but similar to depressive symptoms , they returned after 8  h. midoccipital stimulation increased compulsions , as measured by the y - bocs ( nonsignificantly ) ( p  =  0.07 ) . in 2001 , sachdev et al .   tried to replicate this study in 12 patients with treatment - resistant ocd
( n  =  6 ) and left ( n  =  6 ) dlpfc stimulation was applied in an open fashion at 10  hz , 100% motor threshold for 10 sessions of 2.5  min . at 4  weeks of follow - up
, rtms led to a mean decrease on the y - bocs of 57% for right dlpfc and 27% for left dlpfc .
all 12 individuals were analyzed together , as there were no differences on any of the parameters measured , and showed a significant decrease of 42% on the y - bocs at 1-month follow - up ( p  =  0.003 ) . however , after corrections for depression scores on the montgomery - asberg depression rating scale , the significance disappeared ( p  =  0.06 ) . in the same year , the first randomized , sham - controlled , double - blind rtms ocd trial was completed .
alonso et al .   randomly assigned 18 patients with ocd to real rtms ( n  =  10 ) or sham rtms ( n  =  8) at the right dlpfc .
the rtms lasted 20  min at 1  hz for both conditions , but the motor threshold was 110% for real rtms and 20% for sham rtms .
this study failed to find significant improvement on the y - bocs or hamilton depression rating scale ( ham - d ) after 18 sessions . in 2006 , this randomized , sham - controlled , double - blind design was repeated stimulating the left instead of the right dlpfc in 30 treatment - resistant ocd patients .
patients were given 10 daily sessions of sham or real rtms ( 1  hz , 110% motor threshold ) in addition to ongoing serotonin reuptake inhibitor treatment .
after 2  weeks of follow - up , obsessive - compulsive symptoms improved , with mean y - bocs reductions of 28% , but no differences between sham and real rtms were observed .
the authors concluded that rtms did not result in an effect on ocd by stimulating the left dlpfc .
similarly , in a study by sachdev et al . , high - frequency ( 10  hz , 110% motor threshold ) rtms of the left dlpfc yielded significant y - bocs decreases ( 6.0 points , 23.1% ) over 2  weeks in 10 ocd patients , but the effects were similar after sham rtms in 8 patients ( 5.0 points , 20.4% ) . finally , in an indian sham - controlled study , active rtms at 10  hz , 110% motor threshold ( n  =  21 ) and sham rtms ( n  =  21 ) of the right dlpfc elicited similar improvement in obsessions and compulsions 2  weeks after the 10th session . the y - bocs reduction for active rtms was 5.0 points ( 19.5% ) , and 4.2 points ( 17.7% ) for sham rtms .
interestingly , depressive scores , as measured by the ham - d , were reduced significantly over time in the real rtms group compared with the sham rtms group ( p  >  0.04 ) .
a total of 76.2% of those receiving real rtms were partial responders ( 25% reduction in ham - d scores from baseline ) , compared with 66.7% in the sham group .
the authors concluded that right dlpfc rtms has no effect on ocd but is modestly effective in the treatment of comorbid depressive symptoms . in conclusion , in open - label studies , high - frequency rtms of the right and/or left dlpfc appears to be effective in reducing obsessive - compulsive symptoms .
however , this could not be replicated in double - blind , sham - controlled studies . in those studies , neither low nor high rtms and
neither rtms to the left nor to the right dlpfc appeared to be more effective than sham rtms .
in 2009 , ruffini and colleagues   examined the ofc as a new target for rtms in drug - resistant ocd patients .
the participants received 10  min of 1-hz rtms at 80% motor threshold for 15 sessions to the left ofc ; however , the coil was placed parallel ( active , n  =  16 ) or perpendicular ( sham , n  =  7 ) to the scalp .
they found significant reduction of y - bocs scores comparing active versus sham treatment for 10  weeks after the end of rtms ( p  <  0.02 ) , with loss of significance after 12  weeks ( p  <  0.06 ) .
y - bocs reduction was 19.7% immediately after rtms and 14.7% after 12  weeks of follow - up , but only 6.7% and 5.7% , respectively , for the sham condition .
there was also a benefit in terms of depressive and anxiety symptoms , but not at a significant level in the two groups .
similar to findings for dlpfc rtms , this study suggests that low - frequency rtms of the ofc may only acutely improve obsessive - compulsive symptoms .
two groups investigated the efficacy of low rtms to the sma in addition to ongoing pharmacotherapy . in 2006 , mantovani et al .  
conducted an open - label study of 10 patients with ocd , tourette s syndrome , or both .
individuals were treated with active rtms to the sma for 10 daily sessions at 1  hz , 100% motor threshold .
after 2  weeks of daily rtms , the y - bocs reduction ( 28.6% ) and ham - d reduction ( 47.8% ) were both significant , and they remained stable after 3  months follow - up in the ocd as well as in the ocd / tourette s syndrome group . in 2010 ,
the same group examined rtms ( at 1  hz and 100% motor threshold ) to the sma bilaterally in a randomized , sham - controlled , double - blind design .
after 4  weeks of stimulation , the y - bocs decreased significantly ( p  <  0.001 ) in the active group ( 6 points , 25.4% ) and the sham group ( 3.2 points , 12.0% ) without significant differences between the two treatment conditions .
finally , an open , sham - controlled study investigated the possible therapeutic effects and safety of sequentially combined low - frequency ( 1  hz , 110% threshold ) rtms to the right dlpfc and the sma in 10 patients with treatment - resistant ocd .
similar improvements in obsessive - compulsive and depressive symptoms were observed for sham and real rtms at 2  weeks after the last of 14 sessions .
the y - bocs reductions were 2.9 points ( 10.9% ) and 3.4 points ( 12.9% ) for real and sham rtms , respectively .
rtms was a safe method , and there was no significant change in cognitive functioning after stimulation .
similar to dlpfc and ofc stimulation , rtms to the sma was a safe method to immediately improve obsessive - compulsive symptoms ; however , improvement did not linger on over time . in conclusion ,
efficacy of low- and high - frequency rtms to the left or right dlpfc , the ofc , or the sma has been investigated in a total of 110 obsessive - compulsive patients over the past decade .
although open studies have initially demonstrated beneficial effects of rtms on obsessive - compulsive and depressive symptoms during the first hours after stimulation , these effects disappeared during follow - up and , more importantly , rtms did not show any advantages over sham stimulation in double - blind , sham - controlled studies .
although extremely rare , the most severe acute adverse effect related to rtms is the induction of epileptic seizures .
the chance of getting a seizure during high - frequency rtms is greater than during low - frequency rtms .
other side effects that have been reported are induction of hypomania , local pain , headache , paresthesia , hearing changes , and thyroid - stimulating hormone and blood lactate level changes .
the two latter have only been reported in high rtms . in the studies of rtms in ocd patients ,
low - frequency rtms study patients occasionally reported headache or localized scalp pain [ 14 , 16 , 17 ] , whereas in the high - frequency rtms patients , side effects were more often noted .
the most common complaint in those studies was headache , followed by localized scalp pain , facial nerve stimulation , fainting , and weepiness [ 12 , 20 , 21 ] .
none of the side effects held on longer than 4  weeks after stimulation , and neither serious adverse events such as seizures and memory problems nor cognition problems were disclosed .
since 1997 , rtms has been applied as an experimental treatment in cases of refractory ocd .
local induction of a depolarizing magnetic field pulse may decrease obsessive - compulsive symptoms by normalizing hypermetabolism in orbitofrontal - striatal circuits .
the technique is noninvasive and yields no side effects or mild side effects , of which headache is the most common . because of the lack of studies with comparable stimulation or treatment parameters and with reliable designs , it is difficult to draw clear conclusions ; this corresponds with a cochrane review from 2003 about tms treatment in ocd .
explorations of rtms to the dlpfc , ofc , or sma in a total of 10 studies have demonstrated only acute efficacy for obsessive - compulsive symptoms of rtms and no differences with sham treatment . to generalize the results of these studies ,
careful consideration of target regions and stimulation parameters , longer follow - up , and the use of a double - blind , sham - controlled design may allow us to draw founded conclusions in the future .
besides , as the efficacy of rtms is often time limited , the necessity of a second rtms after several weeks should be investigated .
moreover , functional mri studies of rtms in ocd are needed to clarify the specific stimulation region of rtms . nevertheless , rtms may play an important role in research settings .
for example , rtms could be used to modulate obsessive - compulsive symptoms and brain activity in functional mri and receptor - binding studies . otherwise , as the improvement of symptoms
is often noted in sham settings , it would be interesting to investigate the neural underpinnings of the placebo effect caused by sham rtms . finally , a novel stimulation paradigm was recently designed : theta - burst stimulation , a low - intensity burst of rtms at 50  hz as a safer , more consistent , and longer lasting rtms .
the results of the first case study with this paradigm in ocd and depression are promising and warrant further exploration [ 25 ] .
 obsessive - compulsive disorder ( ocd ) is a chronic , disabling disorder . 
 ten percent of patients remain treatment refractory despite several treatments . for these severe 
 , treatment - refractory patients , repetitive transcranial magnetic stimulation ( rtms ) has been suggested as a treatment option . since 1997 , in published trials , a total of 110 ocd patients have been treated with rtms . 
 this review aims to provide an update on rtms treatment in patients with ocd . 
 first , the mechanism of action is discussed , followed by the efficacy and side effects of rtms at various brain targets , and finally implications for the future . due to the lack of studies with comparable stimulation or treatment parameters and with reliable designs , 
 it is difficult to draw clear conclusions . in general 
 , rtms appears to be effective in open - label studies ; however , this has not yet been replicated in randomized , sham - controlled trials . 
Introduction
Mechanism of Action
Efficacy of Repetitive Transcranial Magnetic Stimulation in Obsessive-Compulsive Disorder
Dorsolateral Prefrontal Cortex
Orbitofrontal Cortex
Supplementary Motor Area
Side Effects and Safety
Conclusions and Future Directions