Evaluating Unilateral Deep Brain Stimulation in Patients With Obsessive Compulsive Disorder

Evaluating Unilateral Deep Brain Stimulation (DBS) of the Bed Nucleus of the Stria Terminalis (BNST) in Patients With Obsessive Compulsive Disorder (OCD)

The investigators previously showed that deep brain stimulation (DBS) in the bed nucleus of the stria terminalis (BNST) reduces symptoms in patients with severe obsessive-compulsive disorder (OCD). Although most patients now receive bilateral stimulation, multiple studies suggest that stimulation of the left BNST might be equally effective. In this study, the investigators will evaluate the effect of unilateral stimulation in OCD patients who currently receive bilateral BNST stimulation to treat their symptoms. We hypothesize that unilateral stimulation of the left BNST will reduce anxious and depressive symptoms, compared to no stimulation. The study entails a double-blinded, randomized cross-over design during which every patient undergoes four stimulation conditions: stimulation of the left, right or bilateral BNST, or no stimulation. During every condition, which takes about fifteen minutes, the patient is exposed to an individually determined stimulus that normally elicits OCD-related symptoms. The patients are then asked to fill out a short questionnaire to evaluate the severity of their symptoms during the four conditions. At the end of the cross-over phase, the stimulation parameters of each patient are restored.

We will evaluate the effect of unilateral and bilateral stimulation of the BNST. Four conditions will be evaluated: left BNST stimulation, right BNST stimulation, bilateral BNST stimulation or no stimulation (OFF). Note that the order of these conditions is stratified beforehand (www.random.org). Each condition takes around 15 minutes.

Both the patient and the psychiatrist are blinded during the cross-over phase, until the end of the study. The investigator who will evaluate behavior from the videorecordings, will also be blinded. Unblinded are: the principal investigator (who has access to all data) and the technical staff in charge of stimulation settings.

For every question on the VAS, there will be a line of 10 centimeters as an outcome measure. The patient will place a mark on this line, in correspondence to their symptoms. The minimum is 0%, which corresponds to no symptoms at all. The maximum is 100% (marker at the end of the 10 centimeter line), and indicates the most severe symptoms. Every millimiter that the mark is removed from the left boundary of the line, is considered as 1%. Measurements of mood and anxiety/stress will be scored using 2 VAS scales. We will only look at sub score, not total scores. A higher score corresponds to more severe symptoms. By using a continuous line as an outcome rather than fixed numbers (1-2-3-...), our rating is far more sensitive to small deviations in how symptoms are experienced.

VAS ratings of obsessive thoughts, urge to perform compulsive behavior, avoidance and global wellbeing

For every question on the VAS, there will be a line of 10 centimeters as an outcome measure. The patient will place a mark on this line, in correspondence to their symptoms. The minimum is 0%, which corresponds to no symptoms at all. The maximum is 100% (marker at the end of the 10 centimeter line), and indicates the most severe symptoms. For global wellbeing, a higher score corresponds to better therapeutic effects. Every millimiter that the mark is removed from the left boundary of the line, is considered as 1%. Obsessive thoughts, urge to perform compulsions, avoidance and global wellbeing will be measured using four separate VAS scales. We will only look at sub score, not total scores. By using a continuous line as an outcome rather than fixed numbers (1-2-3-...), our rating is far more sensitive to small deviations in how symptoms are experienced. For obsessive thoughts, urge to perform compulsions and avoidance, a higher score indicates more severe symptoms.

Inclusion criteria: Clinical diagnosis of obsessive-compulsive disorder Implanted with DBS system in the bilateral BST (or max. 4mm removed from the BST outline) At least three months of chronic BST stimulation Compulsive behavior can be provoked within a clinical setting Exclusion criteria: Personality changes evoked by chronic DBS Cognitive impairment