Postural instability and gait disorders after subthalamic nucleus deep brain stimulation in Parkinson's disease: a PET study.

INTRODUCTION: Patients with Parkinson's disease sometimes report postural instability and gait disorders (PIGD) after subthalamic nucleus deep brain stimulation (STN-DBS). Whether this is the direct consequence of DBS or the result of natural disease progression is still subject to debate. OBJECTIVE: To compare changes in brain metabolism during STN-DBS between patients with and without PIGD after surgery. METHODS: We extracted consecutive patients from a database where all Rennes Hospital patients undergoing STN-DBS are registered, with regular prospective updates of their clinical data. Patients were divided into two groups (PIGD and No PIGD) according to changes after surgery, as measured with a composite score based on the selected Unified Parkinson's Disease Rating Scale items. All patients underwent positron emission tomography with 18[F]-fluorodeoxyglucose 3 months before and after surgery. We ran an ANOVA with two factors (group: PIGD vs. No PIGD; and phase: preoperative vs. postoperative) on SPM8 to compare changes in brain metabolism between the two groups. RESULTS: Participants were 56 patients, including 10 in the PIGD group. The two groups had similar baseline (i.e., before surgery) characteristics. We found two clusters of increased metabolism in the PIGD group relative to the No PIGD group: dorsal midbrain/pons, including locomotor mesencephalic region and reticular pontine formation, and right motor cerebellum. CONCLUSION: We found different metabolic changes during DBS-STN among patients with PIGD, concerning brain regions that are already known to be involved in gait disorders in Parkinson's disease, suggesting that DBS is responsible for the appearance of PIGD.

Subthalamic deep brain stimulation influences complex emotional musical experience in Parkinson's disease.

Subthalamic deep brain stimulation (STN DBS) is an effective treatment for reducing the motor symptoms of patients with Parkinson's disease (PD), but several side effects have been reported, concerning the processing of emotions. Music has been shown to evoke powerful emotional experiences - not only basic emotions, but also complex, so-called aesthetic experiences. The goal of the present study was therefore to investigate how STN DBS influences the experience of both basic and more complex musical emotions in patients with PD. In a three-group between-participants design, we compared healthy controls (HC), patients receiving STN DBS (PD-DBS), and patients who were candidates for STN DBS and receiving medication only (PD-MO) on their assessments of subjectively experienced musical emotions. Results showed that in general, the experience of musical emotions differed only marginally between the PD-MO, PD-DBS, and HC groups. Nonetheless, we were able to discern subtle but distinct effects of PD and STN DBS in the emotional responses. Happy music, for instance, seemed to induce a heightened experience of negative emotions (tension) in PD-MO patients. STN DBS appeared to normalize this particular effect, but increased nostalgic feelings - a rather complex affective experience - in response to the same emotional stimuli. This should not be taken as indicating a bias for nostalgia in the PD-DBS subgroup, as these patients found music inducing melancholy to be less nostalgic and more joyful than HC did. In conclusion, our study showed that music elicits slightly altered emotional experiences in patients with and without STN DBS. In particular, STN DBS seems to induce less distinct emotional responses, blurring the boundaries between complex musical emotions.