This study aims to evaluate the therapeutic effect of low frequency rTMS over the right DLPFC, versus right OFC versus Sham group of obsessive-compulsive disorder (OCD) patients. Sixty patients will be recruited from the out-patient psychiatric clinic of a university hospital, and randomized into three equal groups. The 1st group will receive 10 sessions of low frequency rTMS targeting right DLPFC by means of a butterfly coil, 120% RMT, 1 Hz, 3 trains, each of 500 pulses with a 40 seconds inter-train interval allowing the coil to cool. The 2nd group will receive 10 sessions of low-frequency rTMS over the right orbitofrontal cortex (OFC), the international 10-20 EEG system will be used to position the coil over the right OFC, at the right frontopolar 2 (Fp2) electrode site, using the following parameters: 120% motor threshold, 1 Hz, 3 trains, each of 500 pulses with a 40 seconds inter-train interval allowing the coil to cool. The 3rd group will receive sham stimulations with the same pulse delivery as the other groups but with the coil placed perpendicular to the scalp.

The resting motor threshold (RMT) and cortical silent period (CSP) at different intensities from 110 % to 150 % will be measured before and after the end of sessions. All assessments like (Y-BOCS), (HAM-A), Beck Depression Inventory, (CGI-S), (MoCA) will be performed before and after end of the sessions and 3 months later.

This study aims to evaluate the therapeutic effect of low frequency rTMS over the right DLPFC, versus right OFC versus Sham group of OCD patients. Sixty patients will be recruited from the out-patient psychiatric clinic of a university hospital, the patients will be randomized into three groups (20 patients for each group) using closed envelopes.

The first group (20 patients) will receive 10 sessions of low frequency rTMS targeting right DLPFC by means of a Butterfly coil, The DLPFC stimulation site was defined as the region 5 cm dorsolateral in the same sagittal plane as the optimal site for MT production in the first dorsal interosseous, using the following parameters: 120% RMT, 1 Hz, 3 trains, each of 500 pulses with a 40 seconds inter-train interval allowing the coil to cool.

The second group (20 patients) will receive 10 sessions of low-frequency rTMS over the right orbitofrontal cortex (OFC) by means of a butterfly coil, the international 10-20 EEG system will be used to position the coil over the right OFC, at the right frontopolar 2 (Fp2) electrode site, using the following parameters: 120% motor threshold, 1 Hz, 3 trains, each of 500 pulses with a 40 seconds inter-train interval allowing the coil to cool.

The third group (the sham condition) (20 patients) group will receive sham stimulations with the same pulse delivery as the other groups but with the coil placed perpendicular to the scalp.

The resting motor threshold (RMT) and cortical silent period (CSP) at different intensities from 110 % to 150 % will be measured before and after the end of sessions. All assessments like (Y-BOCS), (HAM-A), Beck Depression Inventory, (CGI-S), (MoCA) will be performed before and after end of the sessions and 3 months later.

Inclusion Criteria:

• being 18 or over
• being assigned a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) or DSM-V diagnosis of OCD by the referring psychiatrist

Exclusion Criteria:

• (1) presenting established cognitive or communication problems which makes it challenging to understand the questionnaires and take part in the therapeutic encounters
• (2) suffering from other severe psychiatric disorders, metabolic, or neurological disorders .
• (3) Patients with pacemaker, or metallic devices