title: A closer look at unilateral versus bilateral deep brain stimulation: results of the National Institutes of Health COMPARE cohort.
abstract: OBJECTIVE
  In this paper, the authors' aim was to examine reasons underpinning decisions to undergo, or alternatively forgo, a second-sided deep brain stimulation (DBS) implantation in patients with Parkinson disease (PD).
  
  
  METHODS
  Fifty-two patients with Parkinson disease (PD) were randomized to receive DBS to the subthalamic nucleus or globus pallidus internus (GPi) as part of the COMPARE trial. Forty-four patients had complete data sets. All patients were offered a choice at 6 months after unilateral implantation whether to receive a contralateral DBS implant. All patients had advanced PD. The mean patient age was 59.8 years (range 43-76 years), and the mean duration of disease was 12.2 years (range 5-21 years). The mean baseline Unified Parkinson's Disease Rating Scale (UPDRS)-III motor score was 42.7. The main outcome measures used in this study were the UPDRS-III Motor Scale and the UPDRS-IV Dyskinesia Scale.
  
  
  RESULTS
  Twenty-one (48%) of the 44 patients in the cohort did not undergo bilateral implantation and have been successfully treated for an average of 3.5 years; of these, 14 (67%) had a GPi target. The most common reason for adding a second side was inadequacy to address motor symptoms. Patient satisfaction with motor outcomes after unilateral DBS implantation was the most common reason for not undergoing bilateral implantation. Those who chose a second DBS procedure had significantly higher baseline UPDRS-III motor and ipsilateral UPDRS-III scores, and a significantly lower asymmetrical index. The logistic regression analysis revealed that the odds of proceeding to bilateral DBS was 5.2 times higher for STN than for GPi DBS. For every 1% increase in asymmetry, the odds of bilateral DBS decreased [corrected] by 0.96.
  
  
  CONCLUSIONS
  Unilateral DBS is an effective treatment for a subset of patients with PD. Baseline asymmetry is an important factor in the effectiveness and decision-making process between unilateral and bilateral DBS. Patients with GPi DBS in this cohort were more likely to choose to remain with unilateral implantation.
authors.affiliation: Department of Neurology, University of Forlida Movement Disorders Center, College of Medicine, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Houtan A
authors.initials: HA
authors.lastname: Taba
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Wu
authors.forename: Kelly D
authors.initials: KD
authors.lastname: Foote
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Hass
authors.forename: Hubert H
authors.initials: HH
authors.lastname: Fernandez
authors.forename: Irene A
authors.initials: IA
authors.lastname: Malaty
authors.forename: Ramon L
authors.initials: RL
authors.lastname: Rodriguez
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Dai
authors.forename: Pamela R
authors.initials: PR
authors.lastname: Zeilman
authors.forename: Charles E
authors.initials: CE
authors.lastname: Jacobson
authors.forename: Michael S
authors.initials: MS
authors.lastname: Okun
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D046690:Deep Brain Stimulation; D006801:Humans; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D010300:Parkinson Disease / Q000628:therapy*; D014481:United States