A non-negligible part of patients with obsessive-compulsive disorder (OCD) experiences inadequate response to pharmacological and cognitive therapies. Therefore, new approaches are required to overcome this problem. The present pilot study estimates the capacity of theta burst stimulation (TBS) in reducing OCD symptoms, also focusing on the neurophysiological basis of TBS aftereffects. Ten patients with OCD who were unsatisfactorily responsive to the pharmacological and neuropsychological treatment, participated to the present randomized crossover pilot study, in which they were subjected to a real or sham intermittent TBS (iTBS) paradigm over the left dorsolateral prefrontal cortex (L-DLPFC) as add-on treatment. They were randomly assigned to a real or sham iTBS in a 1:1 allocation ratio. Patients received the TBS treatment every morning, 5 days a week for 1 month, and were clinically and electrophysiologically evaluated (EEG phase synchronization and coherence) before, immediately after (T0), and one (T1), three (T3) and six (T6) months after the end of the TBS treatment. Then, each patient was subjected to the alternative treatment (that was not practiced before), and followed up to 6 months. We found that all the patients improved in OCD symptomatology up to T1, while four among them improved up to T3. These patients were those showing a more extensive reshape of frontal areas phase synchronization and frontoparietal coherence compared to the other participants. Our pilot study suggests that iTBS over L-DLPFC may represent a feasible approach to improve OCD symptoms. The efficacy of iTBS seems to depend on the extent of frontal and frontoparietal connectivity modulation.
Keywords: Coherence; Connectivity; Cortico-striato-thalamo-cortical network; Dorsolateral-prefrontal cortex; Obsessive–compulsive disorder; Theta burst stimulation.