title: A pilot study: Microlesion effects and tremor outcome in the ventrointermediate deep brain stimulation (VIM-DBS).
abstract: OBJECTIVE
  To perform a pilot study to investigate the relationship between the microlesion effect (MLE) seen in deep brain stimulation (DBS) of the ventralis intermedius nucleus (VIM) and subsequent tremor response and DBS parameter settings.
  
  
  METHODS
  Nineteen thalami in 12 patients (11 essential tremor and 1 Parkinson's disease), who underwent unilateral (n=5) and bilateral VIM-DBS (n=7) were assessed at pre- and 24-h post-operation, at their initial DBS activation, and at 6-month follow-up. The severity of tremor was rated (from 0 to 4) for each activity including hand at rest, outstretched, wing beating, finger-nose-finger, dot approximation and spiral drawing (total score ranging from 0 to 24). The difference of total tremor score before and 24-h after electrode implants (MLE) was segregated into 3 groups based on immediate (24h) post-operative tremor improvement: (1) minimal (none or mild, 0-2), (2) moderate (>2-4), and (3) marked (>4). At the initial activation (23.4+/-3.7 days post-operation), the mean OFF tremor scores were still marginally better in marked than the minimal and moderate MLE groups.
  
  
  RESULTS
  At 6 months, 14 of 19 thalami (74%) were eligible for follow-up analysis. The "OFF" stimulation MLE disappeared in all groups. There was no significant difference of mean ON tremor scores among the groups; however, DBS parameter settings, including amplitude and pulse width, trended to be mildly lower in those with a marked MLE.
  
  
  CONCLUSIONS
  MLE has minimal long term clinical effect except for possibly allowing for lower DBS settings.
authors.affiliation: Parkinson's Disease Center and Movement Disorders Clinic, Department of Neurology, Baylor College of Medicine, Houston, TX, USA. info@bumrungrad.com
authors.forename: Oraporn
authors.initials: O
authors.lastname: Sitburana
authors.forename: Michael
authors.initials: M
authors.lastname: Almaguer
authors.forename: William G
authors.initials: WG
authors.lastname: Ondo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D046690:Deep Brain Stimulation / Q000009:adverse effects* / Q000379:methods; D020329:Essential Tremor / Q000503:physiopathology / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*; D010865:Pilot Projects; D013788:Thalamus / Q000473:pathology; D014202:Tremor / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D055815:Young Adult