title: Effect of botulinum neurotoxin treatment in the lateral spread monitoring of microvascular decompression for hemifacial spasm.
abstract: BACKGROUND
  Botulinum neurotoxin (BtNtx) treatment for hemifacial spasm (HFS) prior to microvascular decompression (MVD) is hypothesized to be a factor in the variability of intraoperative neurophysiological monitoring (IONM) during this procedure.
  
  
  METHODS
  We analyzed 282 MVDs performed at the University of Pittsburgh Medical Center between January 1, 2000 and December 31, 2007. We retrospectively compared the lateral spread response (LSR) in the mentalis muscle when stimulus-triggered electromyography (EMG) was elicited from the facial nerve. Previous BtNtx treatment was the grouping factor.
  
  
  RESULTS
  Baseline LSR amplitudes during MVD (prior BtNtx: mean = 341.47 μV; no BtNtx: mean = 241.81 μV) were significantly different between groups (df = 1,281; t = -2.463; P = 0.014). Comparisons of latency and current threshold at baseline, as well as HFS disappearance or LSR persistence after the procedure, did not achieve statistical significance.
  
  
  CONCLUSIONS
  HFS patients treated with BtNtx prior to MVD demonstrated higher LSR baseline amplitudes during IONM. This could be related to muscle poly-reinnervation after recovery from repeated BtNtx use.
authors.affiliation: Center for Clinical Neurophysiology Department Neurological Surgery, University of Pittsburgh, UPMC Presbyterian, Pittsburgh, Pennsylvania 15213, USA. habeychme@upmc.edu
authors.forename: Miguel E
authors.initials: ME
authors.lastname: Habeych
authors.forename: Aalap C
authors.initials: AC
authors.lastname: Shah
authors.forename: Tara N
authors.initials: TN
authors.lastname: Nikonow
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Balzer
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Crammond
authors.forename: Parthasarathy D
authors.initials: PD
authors.lastname: Thirumala
authors.forename: Amin
authors.initials: A
authors.lastname: Kassam
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000328:Adult; D018726:Anti-Dyskinesia Agents / Q000627:therapeutic use*; D001905:Botulinum Toxins / Q000627:therapeutic use*; D019299:Decompression, Surgical / Q000379:methods; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography; D005260:Female; D019569:Hemifacial Spasm / Q000188:drug therapy* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D018482:Muscle, Skeletal / Q000503:physiopathology; D011930:Reaction Time; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D018726:Anti-Dyskinesia Agents; D001905:Botulinum Toxins