Article

Ipsilateral primary motor cortex (M1) reorganisation after unilateral lower-limb
amputation may degrade function of the amputated limb. We hypothesised unilateral
lower-limb amputees would have a bilateral increase in corticomotor excitability,
and increased excitability of ipsilateral M1 would be associated with increased
step-time variability during gait. Twenty transtibial amputees (16 male) aged
60.1 years (range 45-80 years), and 20 age- and gender-matched healthy adult
controls were recruited. Single-pulse transcranial magnetic stimulation assessed
corticomotor excitability. Two indices of corticomotor excitability were
calculated. An index of corticospinal excitability (ICE) determined relative
excitability of ipsilateral and contralateral corticomotor projections to
alpha-motoneurons innervating the quadriceps muscle (QM) of the amputated limb. A
laterality index (LI) assessed relative excitability of contralateral projections
from each hemisphere. Spatial-temporal gait analysis was performed to calculate
step-time variability. Amputees had lower ICE values, indicating relatively
greater excitability of ipsilateral corticomotor projections than controls (P =
0.04). A lower ICE value was associated with increased step-time variability for
amputated (P = 0.04) and non-amputated limbs (P = 0.02). This association
suggests corticomotor projections from ipsilateral M1 to alpha-motoneurons
innervating the amputated limb QM may interfere with gait. Cortical excitability
in amputees was not increased bilaterally, contrary to our hypothesis. There was
no difference in excitability of contralateral M1 between amputees and controls
(P = 0.10), and no difference in LI (P = 0.71). It appears both hemispheres
control one QM, with predominance of contralateral corticomotor excitability in
healthy adults. Following lower-limb amputation, putative ipsilateral
corticomotor excitability is relatively increased in some amputees and may
negatively impact on function.
CI - (c) 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Langue : ANGLAIS

Tiré à part : OUI