title: Spinal cord injury affects I-wave facilitation in human motor cortex.
abstract: Transcranial magnetic stimulation (TMS) is a useful non-invasive approach for studying cortical physiology. To further clarify the mechanisms of cortical reorganization after spinal cord injury (SCI), we used a non-invasive paired TMS protocol for the investigation of the corticospinal I-waves, the so-called I-wave facilitation, in eight patients with cervical SCI. We found that the pattern of I-wave facilitation significantly differs between SCI patients with normal and abnormal central motor conduction (CMCT), and healthy controls. The group with normal CMCT showed increased I-wave facilitation, while the group with abnormal CMCT showed lower I-wave facilitation compared to a control group. The facilitatory I-wave interaction occurs at the level of the motor cortex, and the mechanisms responsible for the production of I-waves are under control of GABA-related inhibition. Therefore, the findings of our small sample preliminary study provide further physiological evidence of increased motor cortical excitability in patients with preserved corticospinal projections. This is possibly due to decreased GABAergic intracortical inhibition. The excitability of networks producing short-interval intracortical facilitation could increase after SCI as a mechanism to enhance activation of residual corticospinal tract pathways and thus compensate for the impaired ability of the motor cortex to generate appropriate voluntary movements. Finally, the I-wave facilitation technique could be used in clinical neurorehabilitation as an additional method of assessing and monitoring function in SCI.
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Department of Neurology, Franz Tappeiner Hospital, Merano, Italy; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria. Electronic address: raffaele.nardone@asbmeran-o.it.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Nardone
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Höller
authors.affiliation: Department of Mathematics, Paris Lodron University, Salzburg, Austria.
authors.forename: Arne C
authors.initials: AC
authors.lastname: Bathke
authors.affiliation: Department of Neurology, Franz Tappeiner Hospital, Merano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Orioli
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Schwenker
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Frey
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Golaszewski
authors.affiliation: Department of Neurology, Franz Tappeiner Hospital, Merano, Italy; Department of Neurological, Neuropsychological, Morphological and Movement Sciences, Section of Clinical Neurology, University of Verona, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Brigo
authors.affiliation: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Eugen
authors.initials: E
authors.lastname: Trinka
mesh_terms: D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology; D011712:Pyramidal Tracts / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation; D034941:Upper Extremity / Q000503:physiopathology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D005680:gamma-Aminobutyric Acid
keywords: Central motor conduction; Corticospinal tract; GABA; I-wave facilitation; Spinal cord injury; Transcranial magnetic stimulation