Deep brain stimulation of the subthalamic nucleus to improve symptoms and cognitive functions in patients with refractory obsessive-compulsive disorder: a longitudinal study

There are conflicting results regarding the effect of deep brain stimulation (DBS) of different regions on the cognitive functions of patients with severe refractory obsessive-compulsive disorder (OCD). Moreover, it is not yet clear whether the rate of improvement in obsession-compulsion symptoms and cognitive functions following DBS is interrelated. We investigated the effect of the subthalamic nucleus (STN)-DBS on both the severity of symptoms and cognitive functions of patients and also investigated the possible interrelationship between the two. Twelve patients (10 males and two females; 56.17 +/- 4.52 years old) were assessed before and 1 month and 3 months after the DBS surgery using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), the N-Back, the selective and divided attention (SDA), the Tower of London (TOL), and the Wisconsin Card Sorting (WCS) tests. We found that the severity of symptoms and cognitive functions improved significantly after DBS and this effect lasted at least up to 3 months. Furthermore, it was revealed that the severity of symptoms and cognitive profiles of patients were significantly correlated. Compulsion severity had the highest correlation with perseveration errors, while obsession severity was most correlated with the number of n-back errors. Based on our findings, it seems that the STN acts at least to some extent as a common functional/anatomical ground for the severity of symptoms and cognitive functions of patients with severe refractory OCD, and it can probably be considered as the region of interest for DBS in this group of patients.