Theta Burst Stimulation (TBS) in Treatment Resistant Obsessive Compulsive Disorder.

It is a parallel group clinical trial where participants will receive bilateral TBS to either the orbital frontal cortex (OFC) or the supplementary motor area (SMA). Each treatment course will involve TBS treatment twice daily for 2 weeks (10 treatment days). Each treatment session will involve the application of 2 TBS trains, 15 minutes apart (a total of 4 trains per day and 40 trains per treatment course). Patients who do not respond to treatment will be crossed over and provided the alternate treatment one month after their initial treatment had ended. During treatment patients will be reclined in a comfortable chair and will be alert and awake. The sensation associated with treatment is usually well tolerated with most people describing it as a tapping sensation. TBS will be applied in a single 40 - second train per application. Three pulses per burst will be applied at 50 Hz and the bursts repeated at 5 Hz. The treatment intensity for both rTMS and TBS will be 120% of resting motor threshold which is measured by administering single pulse TMS to the muscle controlling area of the brain.