title: Vagus nerve stimulation after lead revision.
abstract: OBJECTIVE
  Vagus nerve stimulation (VNS) has demonstrated benefit in patients with medically intractable partial epilepsy. As in other therapies with mechanical devices, hardware failure occurs, most notably within the VNS lead, requiring replacement. However, the spiral-designed lead electrodes wrapped around the vagus nerve are often encased in dense scar tissue hampering dissection and removal. The objective in this study was to characterize VNS lead failure and lead revision surgery and to examine VNS efficacy after placement of a new electrode on the previously used segment of vagus nerve.
  
  
  METHODS
  The authors reviewed all VNS lead revisions performed between October 2001 and August 2011 at the University of Iowa Hospitals and Clinics. Twenty-four patients underwent 25 lead revisions. In all cases, the helical electrodes were removed, and a new lead was placed on the previously used segment of vagus nerve. All inpatient and outpatient records of the 25 lead revisions were retrospectively reviewed.
  
  
  RESULTS
  Four cases were second lead revisions, and 21 cases were first lead revisions. The average time to any revision was 5 years (range 1.8-11.1 years), with essentially no difference between a first and second lead revision. The most common reason for a revision was intrinsic lead failure resulting in high impedance (64%), and the most common symptom was increased seizure frequency (72%). The average duration of surgery for the initial implantation in the 15 patients whose VNS system was initially implanted at the authors' institution was much shorter (94 minutes) than the average duration of lead revision surgery (173 minutes). However, there was a significant trend toward shorter surgical times as more revision surgeries were performed. Sixteen of the 25 cases of lead revision were followed up for more than 3 months. In 15 of these 16 cases, the revision was as effective as the previous VNS lead. In most of these cases, both the severity and frequency of seizures were decreased to levels similar to those following the previous implantation procedure. Only 1 complication occurred, and there were no postoperative infections.
  
  
  CONCLUSIONS
  Lead revision surgery involving the placement of a new electrode at the previously used segment of vagus nerve is effective at decreasing the seizure burden to an extent similar to that obtained following the initial VNS implantation. Even with multiple lead revisions, patients can obtain VNS efficacy similar to that following the initial lead implantation. There is a learning curve with revision surgery, and overall the duration of surgery is longer than for the initial implantation. Note, however, that complications and infection are rare.
authors.affiliation: Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA. brian-dlouhy@uiowa.edu
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Dlouhy
authors.forename: Steven V
authors.initials: SV
authors.lastname: Viljoen
authors.forename: David K
authors.initials: DK
authors.lastname: Kung
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Vogel
authors.forename: Mark A
authors.initials: MA
authors.lastname: Granner
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Howard
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kawasaki
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004828:Epilepsies, Partial / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012086:Reoperation / Q000295:instrumentation / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014630:Vagus Nerve / Q000502:physiology*; D055536:Vagus Nerve Stimulation / Q000295:instrumentation* / Q000379:methods*; D055815:Young Adult