title: Changes in cortical plasticity after mild traumatic brain injury.
abstract: OBJECTIVE
  Even after a mild traumatic brain injury (TBI) symptoms may be long lasting and never resolve completely. The neurophysiologic substrate for such lasting deficits remains unclear. There is a lack of objective measures of early brain abnormalities following mild TBI, which could shed light on the genesis of these lasting impairments.
  
  
  METHODS
  Here we report findings in a previously healthy man tested 2 and 6 weeks after a well-documented concussion. Findings were compared with 12 control subjects. All subjects underwent brain magnetic resonance imaging (MRI) and diffusion-tensor imaging (DTI). Testing included neuropsychological evaluation and physiological assessment with TMS and EEG, excitatory/inhibitory balance and brain plasticity.
  
  
  RESULTS
  While the MRI, DTI and neuropsychological evaluations showed no abnormalities, neurophysiologic tests revealed subclinical abnormalities in our patient: (1) Significantly higher intracortical facilitation than the control group at both time points; (2) Intracortical inhibition presumably mediated by GABAB receptors was absent at week 2, but returned to normal value at week 6; (3) Abnormal mechanisms of plasticity at week 2, that normalize at week 6.
  
  
  CONCLUSIONS
  These findings demonstrate a transient alteration of brain cortical physiology following concussion independent of anatomical findings and neuropsychological function. This case study suggests that TMS measures may serve as sensitive biomarkers of physiologic brain abnormalities after concussion.
authors.affiliation: Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Shahid
authors.initials: S
authors.lastname: Bashir
authors.forename: Marine
authors.initials: M
authors.lastname: Vernet
authors.forename: Woo-Kyoung
authors.initials: WK
authors.lastname: Yoo
authors.forename: Ilan
authors.initials: I
authors.lastname: Mizrahi
authors.forename: Hugo
authors.initials: H
authors.lastname: Theoret
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
mesh_terms: D000328:Adult; D001924:Brain Concussion / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D003072:Cognition Disorders / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D056324:Diffusion Tensor Imaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D009483:Neuropsychological Tests