Smile and laughter induction and intraoperative predictors of response to deep brain stimulation for...

We recently treated six patients for OCD utilizing deep brain stimulation (DBS) of the anterior limb of the internal capsule and the nucleus accumbens region (ALIC-NA). We individually tested leads via a scripted intraoperative protocol designed to determine DBS-induced side effects and mood changes. We previously published qualitative data regarding our observations of induced emotional behaviors in our first five subjects. We have now studied these same behaviors in the full cohort of six patients over 2 years of follow-up and have examined the relationship of these behaviors to intraoperative mood changes and postoperative clinical outcomes. Five patients experienced at least one smile response during testing. At higher voltages of stimulation, some of these smiles progressed to natural laughter. Smiles and laughter were associated with mood elevation. At stimulation locations at which smiles were observed, voltage and mood were significantly correlated (p=0.0004 for right brain and p<0.0001 for left brain). In contrast, at contacts where smiles were not observed, mood was negatively correlated with voltage (p=0.0591 for right brain and p=0.0086 for left). Smile and laughter-inducing sites were located relatively medial, posterior, and deep in the ALIC-NA. The presence of stimulation induced laughter predicted improvement in OCD symptoms at 2 years. The higher the percentage of laugh conditions experienced in an individual patient, the greater the reduction in YBOCS (24 months, p=0.034). Other correlations between clinical outcomes and percent of smile/laugh conditions were not significant. These stimulation-induced behaviors were less frequently observed with 1 and 2-month postoperative test stimulation and were not observed at subsequent test stimulation sessions. Intraoperative stimulation-induced laughter may predict long-term OCD response to DBS. Identifying other potential response predictors for OCD will become increasingly important as more patients are implanted with DBS devices. A larger study is needed to better delineate the relationship between induced intraoperative and postoperative emotional behavior and clinical outcome in patients treated with DBS therapy.