title: Evolution of brain impedance in dystonic patients treated by GPI electrical stimulation.
abstract: Deep Brain Stimulation is an effective treatment of generalized dystonia. Optimal stimulation parameters vary between patients. This article investigates the influence of electrical brain impedance and delivered current on the brain response to stimulation. Twenty-four patients were bilaterally stimulated in the globus pallidus internus through two implanted four-contact electrodes. The variation of brain impedance and current measurements was correlated with stimulation parameters, time course, and clinical outcome. When a contact was activated, a statistically significant and reversible decrease of brain impedance was found. Impedance and current values and their variations with time significantly differed between patients. The absolute impedance did not significantly correlate with the final outcome. We conclude that the reversible decrease of impedance reflects an adaptive long-term mechanism, which could be due to a plasticity phenomenon, but has no prognostic value. Impedance and current measurements give new complementary information for parameter adjustment and trouble shooting and should therefore be included in all patients' follow-up.
authors.affiliation: Departments of Pediatric Neurosurgery (Research Group on Movement Disorders) and Nuclear Medicine, University Hospital, Montpellier; Laboratory of Mathematical and Theoretical Physics, University of Science, Montpellier II; Laboratory of Industrial Physics and Information Processing, University of Montpellier I, France.
authors.forename: Simone
authors.initials: S
authors.lastname: Hemm
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vayssiere
authors.forename: Gérard
authors.initials: G
authors.lastname: Mennessier
authors.forename: Laura
authors.initials: L
authors.lastname: Cif
authors.forename: Michel
authors.initials: M
authors.lastname: Zanca
authors.forename: Patrice
authors.initials: P
authors.lastname: Ravel
authors.forename: Philippe
authors.initials: P
authors.lastname: Frerebeau
authors.forename: Philippe
authors.initials: P
authors.lastname: Coubes