Deep brain stimulation of the subthalamic nucleus and the temporal discounting of primary and secondary rewards.

Although deep brain stimulation of the subthalamic nucleus is an effective surgical treatment for Parkinson's disease, it may expose patients to non-motor side effects such as increased impulsivity and changes in decision-making behavior. Even if several studies have shown that stimulation of the subthalamic nucleus increases the incentive salience of food rewards in both humans and animals, temporal discounting for food rewards has never been investigated in patients who underwent STN-DBS. In this study, we measured inter-temporal choice after STN-DBS, using both primary and secondary rewards. In particular, PD patients who underwent STN-DBS (in ON medication/ON stimulation), PD patients without STN-DBS (in ON medication) and healthy matched controls (C) performed three temporal discounting tasks with food (primary reward), money and discount vouchers (secondary rewards). Participants performed also neuropsychological tests assessing memory and executive functions. Our results show that STN-DBS patients and PD without DBS behave as healthy controls. Even PD patients who after DBS experienced weight gain and/or eating alterations did not show an increased temporal discounting for food rewards. Interestingly, patients taking a higher dosage of dopaminergic medications, fewer years from DBS surgery and, unexpectedly, with better episodic memory were also those who discounted rewards more. In conclusion, this study shows that STN-DBS does not affect temporal discounting of primary and secondary rewards. Furthermore, by revealing interesting correlations between clinical measures and temporal discounting, it also shed light on the clinical outcomes that follow STN-DBS in patients with PD.

Clinical outcome of deep brain stimulation for dystonia: constant-current or constant-voltage stimulation? A non-randomized study.

BACKGROUND AND PURPOSE: Bilateral globus pallidus deep brain stimulation (GPi-DBS) represents an effective and relatively safe therapy for different forms of refractory dystonia. The aim of this study was to assess, retrospectively, the effect of two different stimulation settings during GPi-DBS in 22 patients affected by primary generalized or multi-segmental dystonia. METHODS: Thirteen patients were stimulated using a voltage-controlled setting whilst in the other nine patients a current-controlled setting was used. Clinical features were evaluated for each patient at baseline, 6 months and 12 months after surgery by means of the Burke-Fahn-Marsden Dystonia Rating Scale. RESULTS: Globus pallidus deep brain stimulation was effective in all patients. However, comparing constant-current and constant-voltage stimulation, a better outcome was found in the current-controlled group during the last 6 months of follow-up. CONCLUSIONS: Current-controlled stimulation is effective during GPi-DBS for primary dystonia and it could be a better choice than voltage-controlled stimulation over long-term follow-up.

Sleep disorders and extrapyramidal diseases: an historical review.

BACKGROUND AND PURPOSE: Sleep disorders have been mentioned since the first descriptions of extrapyramidal diseases in James Parkinson's Essay on the Shaking Palsy, but only recently they have become the subject of attention, thanks to new acquisitions in clinical knowledge and electroencephalographic technology. In the late 1960s, the introduction of L-dopa permitted comparison of sleep patterns in drug-naive patients before and after therapy in conditions very similar to experimental ones. Historically, we can recognise two major lines of study, one dealing with descriptions of sleep behaviours modified by drugs and the other with polysomnographic sleep research carried out before and after treatment. PATIENTS AND METHODS: The data obtained from the first polysomnographic studies led to the definition of sleep macro- and microstructure in patients suffering from Parkinson's disease, but the interpretation of drug-induced changes was not unequivocal. RESULTS: According to some authors, the improvement in sleep architecture was due mainly to improvement of nocturnal motor impairment. Other researchers suggested a primary sleep dysfunction caused by specific neurodegenerative processes in the brain structures regulating the sleep-wake cycle. CONCLUSIONS: The latter hypothesis has recently been supported by the observation that distinct sleep disorders, such as REM behaviour disorder or restless legs syndrome, often herald extrapyramidal diseases or are a frequent adjunctive complaint for these patients.