title: Assessing motor function in young children with transcranial magnetic stimulation.
abstract: OBJECTIVE
  Accurate noninvasive assessment of motor function using functional MRI (fMRI) and magnetoencephalography (MEG) is a challenge in patients who are very young or who are developmentally delayed. In such cases, passive mapping of the sensorimotor cortex is performed under sedation. We examined the feasibility of using transcranial magnetic stimulation (TMS) as a motor mapping tool in awake children younger than 3 years of age.
  
  
  METHODS
  Six children underwent motor mapping with TMS while awake as well as passive sensorimotor mapping under conscious sedation with MEG during tactile stimulation (n = 5) and fMRI during passive hand movements (n = 4).
  
  
  RESULTS
  Stimulation of the motor cortex via TMS successfully elicited evoked responses in contralateral hand muscles in 5 patients. The location of primary motor cortex in the precentral gyrus identified by TMS corresponded with the postcentral location of the primary sensory cortex identified by MEG in 2 patients and to the sensorimotor cortex identified by fMRI in 3 children. In this cohort, we demonstrate that TMS can illuminate abnormalities in motor physiology including motor reorganization. We also demonstrate the feasibility of using TMS-derived contralateral silent periods to approximate the location of motor cortex in the absence of an evoked response. When compared to chronological age, performance functioning level appears to be better in predicting successful mapping outcome with TMS.
  
  
  CONCLUSIONS
  Our findings indicate that awake TMS is a safe alternative to MEG and fMRI performed under sedation to localize the motor cortex and provides additional insight into the underlying pathophysiology and motor plasticity in toddlers.
authors.affiliation: Division of Clinical Neurosciences, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee; Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee; Department of Neurobiology and Anatomy, University of Tennessee Health Science Center, Memphis, Tennessee. Electronic address: snaraya2@uthsc.edu.
authors.forename: Shalini
authors.initials: S
authors.lastname: Narayana
authors.affiliation: Division of Clinical Neurosciences, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee; Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee.
authors.forename: Roozbeh
authors.initials: R
authors.lastname: Rezaie
authors.affiliation: Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: McAfee
authors.affiliation: Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee; Department of Radiology, University of Tennessee Health Science Center, Memphis, Tennessee; Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Asim F
authors.initials: AF
authors.lastname: Choudhri
authors.affiliation: Division of Clinical Neurosciences, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee; Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee.
authors.forename: Abbas
authors.initials: A
authors.lastname: Babajani-Feremi
authors.affiliation: Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee; Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Stephen
authors.initials: S
authors.lastname: Fulton
authors.affiliation: Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee; Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Boop
authors.affiliation: Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee; Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: James W
authors.initials: JW
authors.lastname: Wheless
authors.affiliation: Division of Clinical Neurosciences, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee; Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee; Department of Neurobiology and Anatomy, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Papanicolaou
mesh_terms: D001931:Brain Mapping / Q000379:methods*; D002675:Child, Preschool; D019054:Evoked Potentials, Motor; D005240:Feasibility Studies; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D010812:Physical Stimulation; D012189:Retrospective Studies; D066191:Sensorimotor Cortex / Q000502:physiology; D055698:Touch Perception / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: MEG; TMS; functional MRI; magnetoencephalography; motor cortex; motor mapping; transcranial magnetic stimulation; young children