title: A multi-center analysis evaluating factors associated with spinal cord stimulation outcome in chronic pain patients.
abstract: BACKGROUND
  In addition to its conventional use as a treatment for refractory neuropathic extremity pain, spinal cord stimulation (SCS) has recently emerged as a possible treatment for visceral and arthritic pain. But concurrent with the expansion of possible conditions amenable to SCS, other studies have questioned the long-term efficacy of SCS for traditional indications. These disparate findings argue strongly for the refinement of selection criteria. The purpose of this study is to identify correlates of outcome for SCS.
  
  
  METHODS
  Data were retrospectively collected on 244 patients who underwent a SCS trial at two academic medical centers. Success was predefined as ≥50% pain relief sustained for ≥6 months. Variables analyzed for their association with outcome included demographics, location of pain, diagnosis, presence of coexisting diseases, pain descriptors, opioid and adjuvant medication use, duration and pain relief during trial, and complications.
  
  
  RESULTS
  The presence of allodynia and/or hyperalgesia correlated with both a positive SCS trial (P = 0.01) and long-term implantation outcome (P = 0.05). History of substance abuse was associated with a negative permanent SCS outcome (P = 0.05) but bore no relationship to trial results. The variable most strongly associated with an SCS outcome was experiencing <50% pain relief during the trial, which strongly presaged a negative result (P < 0.001).
  
  
  CONCLUSIONS
  Although weak associations with outcome were noted for several clinical variables, none was strongly associated with trial and permanent implantation results. The strongest predictor of a negative SCS outcome was obtaining <50% pain relief during the trial period.
authors.affiliation: Pain Medicine Division, Department of Anesthesiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21287, USA. kwilli64@jmi.edu
authors.forename: Kayode A
authors.initials: KA
authors.lastname: Williams
authors.forename: Marlis
authors.initials: M
authors.lastname: Gonzalez-Fernandez
authors.forename: Sayeh
authors.initials: S
authors.lastname: Hamzehzadeh
authors.forename: Indy
authors.initials: I
authors.lastname: Wilkinson
authors.forename: Michael A
authors.initials: MA
authors.lastname: Erdek
authors.forename: Anthony
authors.initials: A
authors.lastname: Plunkett
authors.forename: Scott
authors.initials: S
authors.lastname: Griffith
authors.forename: Matthew
authors.initials: M
authors.lastname: Crooks
authors.forename: Thomas
authors.initials: T
authors.lastname: Larkin
authors.forename: Steven P
authors.initials: SP
authors.lastname: Cohen
mesh_terms: D000328:Adult; D059350:Chronic Pain / Q000628:therapy*; D004599:Electric Stimulation Therapy / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013116:Spinal Cord / Q000502:physiology*; D016896:Treatment Outcome