title: Atrophy and other potential factors affecting long term deep brain stimulation response: a case series.
abstract: OBJECTIVE
  To describe three DBS cases which presented with new side effects or loss of benefit from stimulation after long-term follow-up and to discuss the potential contributing factors.
  
  
  METHODS
  A University of Florida (UF) database (INFORM) search was performed, identifying three patients, two Parkinson's disease (PD) and one Essential Tremor (ET), with an unexpected change in long-term programming thresholds as compared to initial evaluation. Clinical follow-up, programming, imaging studies, and lead measurements were reviewed. The UF Institutional Review Board (IRB) approved this study.
  
  
  RESULTS
  A substantial increase in the 3rd ventricular width (120%), Evans index (6%), ventricular index (5%), and cella media index (17%) was uncovered. A change in thresholds across lead contacts with a decrease in current densities as well as a relative lateral change of lead location was also observed. Hardware-related complications, lead migration, and impedance variability were not identified.
  
  
  CONCLUSIONS
  Potential factors contributing to long-term side effects should be examined during a DBS troubleshooting assessment. Clinicians should be aware that in DBS therapy there is delivery of electricity to a changing brain, and atrophy may possibly affect DBS programming settings as part of long-term follow-up.
authors.affiliation: Department of Neurology, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Martinez-Ramirez
authors.affiliation: Department of Neurosurgery, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Takashi
authors.initials: T
authors.lastname: Morishita
authors.affiliation: Department of Neurology, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Pamela R
authors.initials: PR
authors.lastname: Zeilman
authors.affiliation: Department of Neurology, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Peng-Chen
authors.affiliation: Department of Neurosurgery, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Kelly D
authors.initials: KD
authors.lastname: Foote
authors.affiliation: Department of Neurology, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America; Department of Neurosurgery, University of Florida College of Medicine, Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Okun
mesh_terms: D000368:Aged; D001284:Atrophy; D001921:Brain / Q000473:pathology*; D002552:Cerebral Ventricles / Q000473:pathology; D046690:Deep Brain Stimulation; D004566:Electrodes; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome