N-of-1 trial following deep brain stimulation in a patient with obsessive–compulsive disorder

N-of-1 trials are an effective evidence-based approach in individual patient management. It has been suggested that deep brain stimulation (DBS) of the ventral capsule/ventral striatum (VC/VS) is effective in the treatment of refractory obsessive–compulsive disorder (OCD). However, it has not been documented in the literature whether a perioperative acute stimulation test can provide substantial information for chronic stimulation. A 21-year-old man with a 6-year history of medication-refractory OCD underwent bilateral DBS on the VC/VS. Two weeks after surgery, an acute stimulation test was performed in an N-of-1 trial. Olfactory hallucinations, laughter, and euphoria were observed during the acute stimulation test. At follow-up after 17 months, the patient's scores improved from 34 at baseline to 14 on the Yale–Brown Obsessive Compulsive Scale, from 34 to 20 (41.2% improvement) on the Hamilton Anxiety Rating scale, and from 41 to 71 (75% improvement) on the Global Assessment of Functioning scale. According to our N-of-1 trial, olfactory hallucinations, in addition to laughter, induced by a perioperative acute stimulation test may be an indicator of good outcome in OCDDBS during chronic stimulation.