title: Different patterns of medication change after subthalamic or pallidal stimulation for Parkinson's disease: target related effect or selection bias?
abstract: BACKGROUND
  Bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) is favoured over bilateral globus pallidus internus (Gpi) DBS for symptomatic treatment of advanced Parkinson's disease (PD) due to the possibility of reducing medication, despite lack of definitive comparative evidence.
  
  
  OBJECTIVE
  To analyse outcomes after one year of bilateral Gpi or STN DBS, with consideration of influence of selection bias on the pattern of postsurgical medication change.
  
  
  METHODS
  The first patients to undergo bilateral Gpi (n = 10) or STN (n = 10) DBS at our centre were studied. They were assessed presurgically and one year after surgery (CAPIT protocol).
  
  
  RESULTS
  Before surgery the Gpi DBS group had more dyskinesias and received lower doses of medication. At one year, mean reduction in UPDRS off medication score was 35% and 39% in the Gpi and STN groups, respectively (non-significant difference). Dyskinesias reduced in proportion to presurgical severity. The levodopa equivalent dose was significantly reduced only in the STN group (24%). This study high-lights the absence of significant differences between the groups in clinical scales and medication dose at one year. In the multivariate analysis of predictive factors for off-state motor improvement, the presurgical levodopa equivalent dose showed a direct relation in the STN and an inverse relation in the Gpi group.
  
  
  CONCLUSIONS
  Differences in the patterns of medication change after Gpi and STN DBS may be partly due to a patient selection bias. Both procedures may be equally useful for different subgroups of patients with advanced PD, Gpi DBS especially for patients with lower threshold for dyskinesia.
authors.affiliation: Servicio de Neurología, Hospital Virgen de las Nieves, CRT 3 planta, Carretera de Jaén s/n, 18013 Granada, Spain. aminguezc@meditex.es
authors.forename: A
authors.initials: A
authors.lastname: Minguez-Castellanos
authors.forename: F
authors.initials: F
authors.lastname: Escamilla-Sevilla
authors.forename: M J
authors.initials: MJ
authors.lastname: Katati
authors.forename: J M
authors.initials: JM
authors.lastname: Martin-Linares
authors.forename: M
authors.initials: M
authors.lastname: Meersmans
authors.forename: A
authors.initials: A
authors.lastname: Ortega-Moreno
authors.forename: V
authors.initials: V
authors.lastname: Arjona
mesh_terms: D000368:Aged; D000978:Antiparkinson Agents / Q000008:administration & dosage*; D046690:Deep Brain Stimulation; D005260:Female; D005500:Follow-Up Studies; D005917:Globus Pallidus; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000628:therapy*; D012189:Retrospective Studies; D015983:Selection Bias; D020531:Subthalamic Nucleus
chemical_list: D000978:Antiparkinson Agents