title: Functional role of ipsilateral motor areas in multiple sclerosis.
abstract: BACKGROUND
  In patients with multiple sclerosis (MS), motor tasks are associated with increased activation of ipsilateral motor cortical areas. The authors examined the role of two ipsilateral motor areas during performance of a simple motor task in MS patients in relation to their motor impairment and CNS injury.
  
  
  METHODS
  Single pulses of transcranial magnetic stimulation (TMS) were used to interfere transiently with neuronal processing in the contralateral (M1(CONTRA)) or ipsilateral (M1(IPSI)) primary motor cortex or ipsilateral dorsal premotor cortex (PMd(IPSI)) during a simple reaction time (RT) task in 26 right-handed patients with moderately severe stable MS and matched healthy controls. Subjects responded to an auditorily presented Go signal as quickly as possible by performing isometric right-thumb abductions. TMS was applied 100 ms after the Go signal. Motor impairment was evaluated by hand function tests. CNS injury was assessed by magnetic resonance spectroscopy (normalised N-acetyl-aspartate spectra, NAA/Cr), by the total cerebral T2-weighted MRI hyperintense lesion load, and by corticomuscular latency (CML) to the abductor pollicis brevis muscle.
  
  
  RESULTS
  TMS applied to M1(CONTRA) slowed RT in patients and controls. In contrast, stimulation of M1(IPSI) or PMd(IPSI) increased RT only in MS patients. In patients, the relative RT changes following TMS over M1(IPSI) or PMd(IPSI) did not correlate with any of the motor function tests or with NAA/Cr or total cerebral lesion load. However, RT changes following TMS over M1(IPSI) correlated inversely with CML.
  
  
  CONCLUSIONS
  Recruitment of ipsilateral motor areas may be a functionally relevant, yet limited adaptive response to chronic brain injury in MS patients.
authors.affiliation: Department of Neurology, University of Würzburg, Würzburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Zeller
authors.forename: Su-Yin
authors.initials: SY
authors.lastname: Dang
authors.forename: Katja
authors.initials: K
authors.lastname: Stefan
authors.forename: Armin
authors.initials: A
authors.lastname: Biller
authors.forename: Andreas
authors.initials: A
authors.lastname: Bartsch
authors.forename: Dorothee
authors.initials: D
authors.lastname: Saur
authors.forename: Martin
authors.initials: M
authors.lastname: Bendszus
authors.forename: Peter
authors.initials: P
authors.lastname: Rieckmann
authors.forename: Klaus V
authors.initials: KV
authors.lastname: Toyka
authors.forename: Joseph
authors.initials: J
authors.lastname: Classen
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009048:Motor Skills / Q000502:physiology; D009103:Multiple Sclerosis / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult