An OCD patient is deemed treatment-resistant if his symptoms failed to improve after two trials of SRIs. The term “treatment-refractory” is only reserved for patients who failed several trials of SRIs, augmentation with other drugs and behavioral therapy. Such patients may be candidates for more novel treatments like transcranial magnetic stimulation (TMS).
TMS is the least invasive of all physical treatment of OCD. Three areas of the brain are the more common targets of TMS in treating OCD: the dorsolateral prefrontal cortex, which is the most investigated target, the orbitofrontal cortex and the supplemental motor area, which has connections to regions that govern thought and motor processes. These specific brain targets were elucidated after functional imaging of the brains of OCD patients.
In the latest update of the use of repetitive TMS in the treatment of OCD from Blom et al published in 2011, a total of 110 OCD patients have received TMS to one of the three areas. Regardless of the site, all the studies have reported a brief alleviation of obsessive-compulsive and depressive symptoms lasting only for a few hours. Furthermore, in studies where the efficacy of TMS was compared to sham stimulation, there was no statistically significant different between the two groups.
However, Blom et al suggested that further research is still
necessary before TMS is completely taken off the list of treatment
options for OCD. New target regions and stimulation parameters should be
considered. Unlike in cases of depression where one target site has
already been established, TMS studies on OCD do not agree on which site
should be stimulated. With the short-lived benefits of TMS on OCD
patients, the role of a second TMS session after several weeks and
longer follow-up must also be investigated. It should be noted that TMS
is tolerated quite well with headache and localized scalp pain being the
most common side effect.
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