Article

Early unilateral brain lesions can lead to a persistence of ipsilateral
corticospinal projections from the contralesional hemisphere, which can enable
the contralesional hemisphere to exert motor control over the paretic hand. In
contrast to the primary motor representation (M1), the primary somatosensory
representation (S1) of the paretic hand always remains in the lesioned
hemisphere. Here, we report on differences in exercise-induced neuroplasticity
between individuals with such ipsilateral motor projections (ipsi) and
individuals with early unilateral lesions but 'healthy' contralateral motor
projections (contra). METHOD: Sixteen children and young adults with congenital
hemiparesis participated in the study (contralateral [Contra] group: n=7, four
females, three males; age range 10-30y, median age 16y; ipsilateral [Ipsi] group:
n=9, four females, five males; age range 11-31y, median age 12y; Manual Ability
Classification System levels I to II in all individuals in both groups). The
participants underwent a 12-day intervention of constraint-induced movement
therapy (CIMT), consisting of individual training (2h/d) and group training
(8h/d). Before and after CIMT, hand function was tested using the Wolf Motor
Function Test (WMFT) and diverging neuroplastic effects were observed by
transcranial magnetic stimulation (TMS), functional magnetic resonance imaging
(fMRI), and magnetoencephalography (MEG). Statistical analysis of TMS data was
performed using the non-parametric Wilcoxon signed-rank test for pair-wise
comparison; for fMRI standard statistical parametric and non-parametric mapping
(SPM5, SnPM3) procedures (first level/second level) were carried out. Statistical
analyses of MEG data involved analyses of variance (ANOVA) and t-tests. RESULTS:
While MEG demonstrated a significant increase in S1 activation in both groups
(p=0.012), TMS showed a decrease in M1 excitability in the Ipsi group (p=0.036),
but an increase in M1 excitability in the Contra group (p=0.043). Similarly, fMRI
showed a decrease in M1 activation in the Ipsi group, but an increase in
activation in the M1-S1 region in the Contra group (for both groups p<0.001
[SnPM3] within the search volume). INTERPRETATION: Different patterns of
sensorimotor (re)organization in individuals with early unilateral lesions show,
on a cortical level, different patterns of exercise-induced neuroplasticity. The
findings help to improve the understanding of the general principles of
sensorimotor learning and will help to develop more specific therapies for
different pathologies in congenital hemiparesis.
CI - (c) 2013 Mac Keith Press.

Langue : ANGLAIS