title: Intracranial supramaximal facial nerve stimulation: a murine model.
abstract: OBJECTIVE
  Supramaximal facial nerve stimulation is an applied current sufficient to evoke a maximal electromyographic response of facial musculature. It is used during cerebellopontine angle surgery for prognostication of postoperative nerve function. We utilized a rat model to examine safe parameters for intracranial electrical stimulation.
  
  
  METHODS
  Intracranial facial nerve stimulation with electromyographic monitoring of 14 rats was performed. Supramaximal current level was determined and 50 additional pulses of supramaximal (4 rats), 3 times supramaximal (4), 10 times supramaximal (3), or zero (3) current were applied. To monitor progression of facial nerve injury, video recordings of vibrissae movements and eye closure were captured at 1, 3 and 28 days after surgery; animals were sacrificed on day 28, when nerve morphometry was performed.
  
  
  RESULTS
  One rat in the supramaximal stimulation group (of 4), and one rat in the 10 times supramaximal stimulation group (of 3) demonstrated persistent impairment of facial nerve function as evidenced by decreased amplitude of vibrissae sweeping and eye closure impairment. The remainder of rats in all experimental groups demonstrated symmetric and normal facial nerve function at all time points.
  
  
  CONCLUSIONS
  A novel animal model for supramaximal stimulation of the rat intracranial facial nerve is described. A small proportion of animals demonstrated functional evidence of nerve injury postoperatively. Function was preserved in some animals after stimulation with current order of magnitude higher than supramaximal levels. Further study with this model is necessary to definitively isolate the effects of surgical trauma from those of supramaximal electrical stimulation.
authors: Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA. Electronic address: breen.joseph@mayo.edu.
authors: Joseph T
authors: JT
authors: Breen
authors: Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA.
authors: Matthew L
authors: ML
authors: Carlson
authors: Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA.
authors: Stephen G
authors: SG
authors: Voss
authors: Department of Neurologic Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA.
authors: Michael J
authors: MJ
authors: Link
authors: Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA; Department of Neurologic Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA.
authors: Colin L
authors: CL
authors: Driscoll
authors: Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA.
authors: Brian A
authors: BA
authors: Neff
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000379:methods*; D004576:Electromyography; D005152:Facial Muscles / Q000294:innervation / Q000503:physiopathology*; D005154:Facial Nerve / Q000503:physiopathology*; D020220:Facial Nerve Injuries / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D009119:Muscle Contraction; D051381:Rats; D017207:Rats, Sprague-Dawley