The
most ambitious form of treatment for AMN patients
to date is the quantification of movement impairments.
The
purpose of this study is to measure the time course
of sensory loss and weakness and evaluate treatments
in people with AMN. This is being done through
the development of tests that are sensitive enough
to detect defecits and track small changes in
sensation and strength over 6 months to a year.
Secondly, the further aim is to determine the
relative contributions of sensory loss and weakness
to balance and walking. Previously, doocumentation
of AMN progression relied upon clinical observations
and subjective rating scales that required 4 to
5 years to show change. This has made it difficult
to evaluate small changes in sensation and strength,
and has delayed assessment of therapeutic interventions.
In
this study 15 men with AMN, and four heterozygote
carriers (women) were evaluated; a subset has
had repeat tests six months later. All patients
were studies using quantitative balance, walking,
sensory, and strength tests. Standing balance
(sway) was measured using force plate recordings
and 3-D tracking of trunk and leg joint movements
(Pototrak, Northern Digital). Walking was assessed
using a quantitative gait analysis (3-D tracking
of trunk and leg joints) and a Timed 25-Foot Walk
test. Sensation of the hands and feet was quantified
using the Vibration II and lower extremity strength
was measured using a hand-held dynamometer.
Our
results show that all patients were impaired on
these tests relative to established control values;
we can easily distinguish mild to severe deficits
across patients. Sensation was severely impaired
in the feet, not the hands, and is correlated
with deficits in balance. Multiple regression
showed that hip weakness is the most significant
predictor of walking speed; measures of sensation
or balance were not strongly related. Analyses
of walking show that patients walk maintaining
their knees and hips in a flexed posture (active
range of motion of the legs are decreased compared
to controls), and lean at the trunk to compensate
for leg weakness (trunk motion is increased compared
to controls is increased compared to controls).
Preliminary data from the 6-month testing session
show significant changes in balance (sway scores
doubled), and smaller changes in sensation and
strength measures.
From
these results we can distinguish mild to severe
defecits in sensation ans strength in AMN patients
relative to established control values. We also
show that loss of sensation in the feet correlates
with balance impairments. However, weakness
(not sensory loss) is the best predictor for
walking impairments. Preliminary longitudinal
data suggest that our quantitative tests are
sensitive enough to detect small changes in
performance that are not visible clinically
over 6 months to a year.
Back to Trials
To
participate in this or other motion related studies
regarding AMN, please contact Kim Hollandsworth
at The Kennedy Krieger Institute by calling:
(443) 923-2772.
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