title: Dissociation of Structural and Functional Integrities of the Motor System in Amyotrophic Lateral Sclerosis and Behavioral-Variant Frontotemporal Dementia.
abstract: OBJECTIVE
  This study investigated the structural and functional changes in the motor system in amyotrophic lateral sclerosis (ALS; n=25) and behavioral-variant fronto-temporal dementia (bvFTD; n=17) relative to healthy controls (n=37).
  
  
  METHODS
  Structural changes were examined using a region-of-interest approach, applying voxel-based morphometry for gray-matter changes and diffusion tensor imaging for white-matter changes. Functional changes in the motor system were elucidated using threshold-tracking transcranial magnetic stimulation (TMS) measurements of upper motor-neuron excitability.
  
  
  RESULTS
  The structural analyses showed that in ALS there were more white-matter changes in the corticospinal and motor-cortex regions and more gray-matter changes in the cerebellum in comparison to controls. bvFTD showed substantial gray- and white-matter changes across virtually all motor-system regions compared to controls, although the brainstem was affected less than the other regions. Direct comparisons across patient groups showed that the gray- and white-matter motor-system changes inclusive of the motor cortex were greater in bvFTD than in ALS. By contrast, the functional integrity of the motor system was more adversely affected in ALS than in bvFTD, with both patient groups showing increased excitability of upper motor neurons compared to controls.
  
  
  CONCLUSIONS
  Cross-correlation of structural and functional data further revealed a neural dissociation of different motor-system regions and tracts covarying with the TMS excitability across both patient groups. The structural and functional motor-system integrities appear to be dissociated between ALS and bvFTD, which represents useful information for the diagnosis of motor-system changes in these two disorders.
authors.affiliation: Department of Neurology, Hallym University College of Medicine, Seoul, Korea.|Neuroscience Research Australia, Sydney, Australia.
authors.forename: Jong Seok
authors.initials: JS
authors.lastname: Bae
authors.affiliation: Neuroscience Research Australia, Sydney, Australia.|School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Michele
authors.initials: M
authors.lastname: Ferguson
authors.affiliation: Neuroscience Research Australia, Sydney, Australia.
authors.forename: Rachel
authors.initials: R
authors.lastname: Tan
authors.affiliation: Department of Psychiatry, University of Cambridge, Cambridge, UK.
authors.forename: Eneida
authors.initials: E
authors.lastname: Mioshi
authors.affiliation: Neuroscience Research Australia, Sydney, Australia.
authors.forename: Neil
authors.initials: N
authors.lastname: Simon
authors.affiliation: Neuroscience Research Australia, Sydney, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Burrell
authors.affiliation: Department of Neurology, Westmead Clinical School, University of Sydney, Westmead, Australia.
authors.forename: Steve
authors.initials: S
authors.lastname: Vucic
authors.affiliation: Neuroscience Research Australia, Sydney, Australia.|School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: John R
authors.initials: JR
authors.lastname: Hodges
authors.affiliation: Brain and Mind Institute, University of Sydney, Sydney, Australia.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Kiernan
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich, UK. m.hornberger@uea.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: Hornberger
keywords: amyotrophic lateral sclerosis; diffusion tensor imaging; frontotemporal dementia; transcranial magnetic stimulation; voxel-based morphometry