Obsessive-compulsive disorder (OCD) is a severely disabling psychiatric disorder with a worldwide lifetime prevalence of 2-3% (Islam et al., 2015).Despite the efficacy of pharmacological and behavioural treatment methods for most OCD patients, roughly one third do not demonstrate significant symptom improvement, even after aggressive treatment (Foa et al, 2007). The effectiveness of neurosurgical treatment methods (including ablative surgery) for those with severely disabling treatment resistant OCD is substantiated by clinical research (Greenberg, Rauch & Haber, 2010). The brain target of this procedure is usually the area between the anterior and middle third of the anterior limb of the internal capsule.

Inclusion Criteria:

1. Obsessive compulsive disorder as the primary psychiatric diagnosis (according to DSM IV-criteria).
2. Severity: Score higher than 25 on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS).
3. Course of illness had to have been present for at least five years in a chronic or progressive form despite any treatment trials (refractory).
4. Refractory: a lack of response to drug therapy after adequate administration (defined as more than 12 weeks at the maximum tolerated dose) of at least three serotonin-reuptake inhibitors, and clomipramine. Adequate psychotherapy, defined as continuously treatment for more than six months with a certified therapist .

Exclusion Criteria:

1. Schizophrenic disorder; bipolar disorder; substance abuse or dependence (except for dependence on nicotine), as assessed with the use of the Mini-International Neuropsychiatric Interview (MINI 6.0.0);
2. Cluster A or B personality disorder according to DSM-IV criteria, as assessed with the use of the Structured Clinical Interview II.
3. A current severe major depressive episode, determined according to DSM-IV criteria (as assessed with the use of the MINI 6.0.0) and defined by HAMD-17 score of more than 20 and a risk of suicide.
4. Abnormal cognitive status (measured by MoCA)