Switching from constant voltage to constant current in deep brain stimulation: a multicenter experience of mixed implants for movement disorders.

BACKGROUND AND PURPOSE: For many years deep brain stimulation (DBS) devices relied only on voltage-controlled stimulation (CV), but recently current-controlled devices have been developed and approved for new implants as well as for replacement of CV devices after battery drain. Constant-current (CC) stimulation has been demonstrated to be effective in new implanted parkinsonian and dystonic patients, but the effect of switching to CC therapy in patients chronically stimulated with CV implantable pulse generators (IPGs) has not been assessed. This report shows the results of a consecutive retrospective data collection performed at five Italian centers before and after replacement of constant-voltage with constant-current DBS devices, in order to verify the clinical efficacy and safety of this procedure. METHODS: Nineteen patients with Parkinson's disease or dystonic syndrome underwent DBS IPG CV/CC replacement. Clinical features and therapy satisfaction were assessed before surgery, 1 week after and 3 and 6 months after replacement. Programming settings and impedances were recorded before removing the CV device and when the CC IPGs were switched on. RESULTS: The clinical outcome of CC stimulation was similar to that obtained with CV devices and remained stable at 3 and 6 months of follow-up. Impedance values recorded for CV and CC IPGs were similar. Ninety-five percent of patients and physicians were satisfied with mixed implants. No adverse events occurred after IPG replacement. CONCLUSION: Replacing CV with CC IPGs is a safe and effective procedure. Longer follow-up is necessary to better clarify the impact of CC stimulation on clinical outcome after chronic stimulation in CV mode.

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.

A survey of Italian cases of dystonia treated by deep brain stimulation.

AIM: The aim of this study was to report on Italian cases of dystonia treated by deep brain stimulation up to the end of 2005. METHODS: Retrospective survey. Presentation of data collection among all Italian neurosurgical institutions. RESULTS: Seven out of 123 Italian neurosurgical centres were enrolled. Sixty-nine patients were operated. According to different classification criteria, cases were grouped as follows: 37 primary and 32 secondary dystonia; 61 generalized and 8 focal dystonia; 16 patients aged at onset <2 years, 22 aged 3-12 years, 14 aged 13-20 years, 17 aged >20 years. Primary dystonia (DYT) mutation 1 was identified in 21% of primary generalized dystonia. Age at surgery was <15 years in 21.7% of cases (N.=15). Mean time between clinical onset and surgery was 17 years. Globus pallidus internus (GPi) was chosen for implantation in all cases. Type of anesthesia, method of target localization, lead and implanted pulse generator (IPG) model differed among centres. Surgical complications occurred in 19% of patients, but at a higher rate (33%) in the pediatric subgroup. Stimulation parameters varied among centres, but the main scheme was 90-120 micros and 130 Hz. Follow-up duration ranged from 3 to 84 months (longer than 24 months in 50% of patients). Mean Burke-Fahn-Marsden scale (BFM) improvement was 42% for both severity and disability score, ranging from 0% to 92%. Improvement of at least 50% in BFM severity score has been reached by 45% of primary and 37% of secondary dystonia. Clinical results were better in the DYT1 subgroup, with 60% of cases improving more than 50%. Among secondary dystonia, the drug-induced group had very good results too. On the contrary delayed surgery and presence of comorbidity were negatively correlated to the outcome. CONCLUSION: In this series, primary generalized dystonia has a better outcome, especially if associated to DYT1 mutation. Among secondary dystonia, the drug-induced group has very good RESULTS: Correlation analysis of time to surgery and associated comorbidity suggests that earlier surgery is advisable.

Plasmodium falciparum parasitized red blood cells modulate the production of endothelin-1 by human endothelial cells.

AIM: Plasmodium falciparum (P. falciparum) malaria is the most important parasitic infection of humans, responsible for about 2,000,000 deaths every year. Cytoadherence of P. falciparum parasitized erythrocytes (pRBC) to vascular endothelium contributes to the pathogenesis of severe malaria causing microcirculatory obstruction and subsequent tissue hypoxia. Several cytokines and vasoactive mediators are involved in this process. The aim of this paper was to investigate the production of endothelin-1 (ET-1), a potent vasoconstrictor agent, by endothelial cells from large vessels (human umbilical vein endothelial cells, HUVEC) or the microvasculature (human microvascular endothelial cells, HMEC-1), co-cultured with different strains of P. falciparum pRBC under normoxic or hypoxic conditions. METHODS: HMEC-1, immortalized by SV 40 large Tontigen, were maintained in MCDB 131 medium supplement ed with 10% fetal calf serum, 10 ng/ml of epidermal growth factor, 1 microg/ml of hydrocortisone, 2 mM glutamine, 100 U/ml of penicillin, 100 microg/ml of streptomycin and 20 mM Hepes buffer. The levels of ET-1 in the supernatants were measured by immunoenzymatic assay. RESULTS: The results indicated that IL1-beta and hypoxia were able to induce ET-1 production by both HUVEC and HMEC-1. However, the co-incubation of HUVEC or HMEC-1 with pRBC induced a dose-dependent decrease of both constitutive and IL1- or hypoxia-induced ET-1 production. The inhibition was independent from the parasite strain used and from the origin of endothelial cells. CONCLUSION: These results show that pRBC by modulating both constitutive and stimulated ET-1 release from endothelial cells can induce modifications of the vascular tone in different anatomical districts. This could be of relevance in the pathogenesis of severe malaria.