Article

Understanding the mechanisms of neurophysiological alterations with
chronic ankle instability (CAI) may be essential in the development of the
most-effective intervention programs to treat neuromuscular dysfunction in
patients with CAI. Specifically, the presence of CAI may be associated with an
altered supraspinal mechanism within the central nervous system to inhibit neural
drive to the undamaged soleus surrounding the injured ankle joint. OBJECTIVE: To
investigate the influence of CAI on corticospinal excitability and inhibition of
the soleus. DESIGN: A single-blinded, case-control study. SETTING: Research
laboratory. PARTICIPANTS: Sixteen participants with self-reported CAI and 17
healthy control participants volunteered. METHODS: Transcranial magnetic
stimulation was used to assess corticospinal excitability and inhibition of the
soleus muscle. Active motor threshold (AMT), defined as the lowest stimulator
intensity required to elicit a peak-to-peak motor-evoked potential (MEP)
amplitude >/=100 muV in at least four of 8 trials, was found to assess
corticospinal excitability of the soleus. Eight stimuli were delivered at 120% of
AMT, and peak-to-peak MEP amplitudes were recorded for each trial. The amplitude
of 8 MEPs at 120% of AMP were averaged and normalized to the maximum M-response.
Cortical silent period (CSP) was measured as the distance from the end of the MEP
to a return of the mean electromyographic signal plus 2 times the standard
deviation of the baseline (prestimulus) electromyographic signal. The ratio of
the CSP to the MEP at 120% AMT (CSP:MEP120) were calculated to assess
corticospinal inhibition. RESULTS: The CAI group had a greater CSP:MEP120 ratio
compared with the control group (P = .02). No significant differences between
groups were observed for AMT (P = .67) and normalized MEP at 120% of AMT (P =
.42). CONCLUSIONS: The greater CSP:MEP120 ratio in participants with CAI suggests
an altered balance in corticospinal inhibition and excitability to the soleus of
the CAI cohort. Future research is needed to determine the role of corticospinal
inhibition in physical and self-reported function in patients with CAI. LEVEL OF
EVIDENCE: IV.
CI - Copyright (c) 2016 American Academy of Physical Medicine and Rehabilitation.
Published by Elsevier Inc. All rights reserved.

Langue : ANGLAIS