title: Excitability of contralateral and ipsilateral projections of corticobulbar pathways recorded as corticobulbar motor evoked potentials of the cricothyroid muscles.
abstract: OBJECTIVE
  The objective of this study was to evaluate the excitability of contralateral and ipsilateral corticobulbar pathways, using the methodologies of navigated transcranial magnetic stimulation (nTMS) and transcranial electrical stimulation (TES).
  
  
  METHODS
  In 11 healthy subjects, the primary motor cortex (M1) for laryngeal muscles was mapped with nTMS in both hemispheres and the corticobulbar motor evoked potentials (CoMEPs) were recorded from the right cricothyroid muscle. In 15 patients undergoing left craniotomy, CoMEPs were obtained from cricothyroid muscles bilaterally, using TES over C3/Cz and C4/Cz.
  
  
  RESULTS
  In five out of 11 healthy subjects, both contralateral and ipsilateral CoMEPs were recorded from the right cricothyroid muscle. In eight out of 15 patients, contralateral and ipsilateral CoMEPs were elicited with TES over C3/Cz, while in five out of 15 patients contralateral and ipsilateral CoMEPs were elicited with TES over C4/Cz. Contralateral CoMEP amplitude responses were significantly larger compared to ipsilateral CoMEP amplitudes in both groups.
  
  
  CONCLUSIONS
  We obtained significantly larger amplitude responses of contralateral CoMEPs from cricothyroid muscles compared to ipsilateral CoMEP amplitude using nTMS in healthy subjects and TES in patients. This confirms the bilateral nature of corticobulbar pathway projections for laryngeal muscles, with contralateral domination.
  
  
  CONCLUSIONS
  These findings will influence recording of CoMEPs during preoperative and intraoperative mapping of M1 for laryngeal muscle representation, and they facilitate the pathophysiologic research of motor speech disorders.
authors.affiliation: Laboratory for Human and Experimental Neurophysiology (LAHEN), Department of Neuroscience, School of Medicine, University of Split, Split, Croatia. Electronic address: maja.rogic@mefst.hr.
authors.forename: Maja
authors.initials: M
authors.lastname: Rogić Vidaković
authors.affiliation: Department of Neurosurgery, Clinical Unit for Intraoperative Neurophysiologic Monitoring, Clinical Medical Centre 'Sisters of Mercy', Zagreb, Croatia.
authors.forename: Marina Zmajević
authors.initials: MZ
authors.lastname: Schönwald
authors.affiliation: Department of Neurosurgery, Clinical Unit for Intraoperative Neurophysiologic Monitoring, Clinical Medical Centre 'Sisters of Mercy', Zagreb, Croatia.
authors.forename: Krešimir
authors.initials: K
authors.lastname: Rotim
authors.affiliation: Department of Electronics, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia.
authors.forename: Tomislav
authors.initials: T
authors.lastname: Jurić
authors.affiliation: Department of Electronics, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Vulević
authors.affiliation: Department of Ear, Nose and Throat with Head and Neck surgery, Clinical Medical Centre Split, Split, Croatia.
authors.forename: Robert
authors.initials: R
authors.lastname: Tafra
authors.affiliation: Department of Anatomy, Embryology and Histology, University of Split School of Medicine, Split, Croatia.
authors.forename: Adriana
authors.initials: A
authors.lastname: Banožić
authors.affiliation: Department of Neurosurgery, Clinical Unit for Intraoperative Neurophysiologic Monitoring, Clinical Medical Centre 'Sisters of Mercy', Zagreb, Croatia.
authors.forename: Željko
authors.initials: Ž
authors.lastname: Hamata
authors.affiliation: Laboratory for Human and Experimental Neurophysiology (LAHEN), Department of Neuroscience, School of Medicine, University of Split, Split, Croatia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Đogaš
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007821:Laryngeal Muscles / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Corticobulbar tracts; Cricothyroid muscles; Motor cortex; Motor evoked potentials; Transcranial magnetic stimulation; Transcutaneous electric stimulation