Abstract
Background
Peripheral
changes to muscle and motor nerves occur following stroke, which may
further impair functional capacity. We investigated whether a year-long
use of an implanted peroneal FES system reverses stroke-related changes
in muscles and motor nerves in people with foot drop in the chronic
phase after supratentorial stroke.
Methods
Thirteen
persons with a chronic stroke (mean age 56.1 years, median Fugl-Meyer
Assessment leg score 71%) were included and received an implanted
peroneal FES system (ActiGait®). Quantitative muscle ultrasound (QMUS)
images were obtained bilaterally from three leg muscles (i.e. tibialis
anterior, rectus femoris, gastrocnemius). Echogenicity (muscle
ultrasound gray value) and muscle thickness were assessed over a
one-year follow-up and compared to age-, sex-, height- and
weight-corrected reference values. Compound motor action potentials
(CMAPs) and motor evoked potentials (MEPs) were obtained from the
tibialis anterior muscle. Generalized estimated equation modeling was
used to assess changes in QMUS, CMAPs and MEPs outcomes over the
follow-up period.
Results
Echogenicity
of the tibialis anterior decreased significantly during the follow-up
on the paretic side. Z-scores changed from 0.88 at baseline to − 0.15
after 52 weeks. This was accompanied by a significant increase in muscle
thickness on the paretic side, where z-scores changed from − 0.32 at
baseline to 0.48 after 52 weeks. Echogenicity of the rectus femoris
normalized on both the paretic and non-paretic side (z-scores changed
from − 1.09 and − 1.51 to 0.14 and − 0.49, respectively). Amplitudes of
CMAP and MEP (normalized to CMAP) were reduced during follow-up,
particularly on the paretic side (ΔCMAP = 20% and ΔMEP = 14%).
Conclusions
We
show that the structural changes to muscles following stroke are
reversible with FES and that these changes might not be limited to
electrically stimulated muscles. No evidence for improvement of the
motor nerves was found.
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