title: Long-latency response to transcranial magnetic stimulation in patients with hemifacial spasm.
abstract: OBJECTIVE
  We studied the long-latency response of the orbicularis oris muscle elicited with transcranial magnetic stimulation in patients with hemifacial spasm (HFS) and evaluated the excitability of the facial nucleus.
  
  
  METHODS
  We compared the thresholds on both sides in 8 normal volunteers and 7 patients with hemifacial spasm. The thresholds were determined as the lowest intensity required to produce motor evoked potentials with an amplitude of at least 50 microV in the orbicularis oris muscle. Average values were given as means +/- standard deviation. Wilcoxon's rank sum test was used for comparisons between the sides of normal subjects and of patients with HFS with respect to the threshold stimulus.
  
  
  RESULTS
  There was no significant difference between the thresholds on the two sides of the normal subjects (mean 1.88+/-5.30%, P > 0.05). In patients with HFS, there was a significant difference between the thresholds on the spasm side and the normal side (mean 20.7+/-13.0%, P < 0.05) In one patient studied after MVD, the difference between both sides disappeared.
  
  
  CONCLUSIONS
  The difference between the thresholds in patients with HFS and the normalization in threshold after MVD suggested that the mechanism of HFS was hyperexcitability of the facial nucleus.
authors.affiliation: Department of Neurosurgery, Neurophysiology, Keio University School of Medicine, Tokyo, Japan. kojima@med.keio.acjp
authors.forename: A
authors.initials: A
authors.lastname: Kojima
authors.forename: T
authors.initials: T
authors.lastname: Ohira
authors.forename: M
authors.initials: M
authors.lastname: Takase
authors.forename: T
authors.initials: T
authors.lastname: Kawase
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005154:Facial Nerve / Q000502:physiology*; D005260:Female; D019569:Hemifacial Spasm / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D050781:Transcranial Magnetic Stimulation