Functional role of ipsilateral motor areas in multiple sclerosis.
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.
Zeller
Daniel
D
Department of Neurology, University of Würzburg, Würzburg, Germany.
Dang
Su-Yin
SY
Stefan
Katja
K
Biller
Armin
A
Bartsch
Andreas
A
Saur
Dorothee
D
Bendszus
Martin
M
Rieckmann
Peter
P
Toyka
Klaus V
KV
Classen
Joseph
J
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