Add-on HD-tDCS for obsessive-compulsive disorder with comorbid bipolar affective disorder: A case series.

Obsessive-compulsive disorder (OCD) with comorbid bipolar affective disorder (BPAD) is often faced with a therapeutic challenge. Pharmacological treatment strategy engaged towards alleviating symptoms in OCD has the propensity to precipitate a manic switch in patients with comorbid BPAD. Advanced non-invasive brain stimulation techniques like high definition transcranial direct current stimulation (HD-tDCS) may target the symptoms of OCD while preventing a probable manic switch in a vulnerable population. In this case series, we targeted OC symptoms in three patients by giving 2 mA of anodal HD-tDCS at their pre-SMA (localized using 10/10 EEG system) with 4 surrounding return electrodes of opposite polarity for 20 min of two sessions having an intersession gap of 20 min receiving a maximum of 20 sessions. We found that the patients showed significant improvement (more than 25%) in their OC symptoms while having no affective side effects and this effect was replicated in one of the two patients in repeating the treatment for relapse. This case series highlights the efficacy and durability of the effect of HD-tDCS as an add-on treatment modality in three patients who were treated for OC symptoms in the context of a comorbid bipolar disorder, two of them receiving repeat courses on relapse.