Can motor evoked potentials be an objective parameter to assess extremity function at the acute or subacute stroke stage?
OBJECTIVE
To investigate whether motor evoked potential (MEP) amplitude ratio measurements are sufficiently objective to assess functional activities of the extremities. We also delineated the distribution between the presence or absence of MEPs and the Medical Research Council (MRC) scale for muscle strength of the extremities.


METHODS
We enrolled 183 patients with first-ever unilateral hemiplegia after stroke. The MEP parameters were amplitude ratio (amplitude of affected side/amplitude of unaffected side) recorded at the first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. We performed frequency analyses using the MRC scale for muscle strength and the presence or absence of evoked MEPs. Change on the MRC scale, hand function tests (HFTs), and the Modified Barthel Index (MBI) subscore were compared between the evoked MEP and absent MEP groups using the independent t-test. Receiver operating characteristic curves were used to determine the optimal cutoff scores for the MEP amplitude ratio using the HFT results and MBI subscores. Correlations between the MEP amplitude ratio and the MRC scale, HFTs, and MBI subscore were analyzed.


RESULTS
About 10% of patients with MRC scale grades 0-2 showed evoked MEPs at the FDI muscle, and 4% of patients with MRC scale grades 3-5 did not show MEPs. About 18% of patients with MRC scale grades 0-2 showed evoked MEPs at the TA muscle, and 4% of patients with MRC scale grades 3-5 did not show MEPs. MEP amplitude increased with increasing MRC scale grade. The evoked MEP group had more significant changes on the MRC scale, HFT, and the climbing stair score on the MBI than those in the group without MEPs. Larger MEP amplitude ratios were observed in patients who had more difficulty with the HFTs and ambulation. The MEP amplitude ratio was significantly correlated with the MRC scale, HFT, and MBI subscore.


CONCLUSIONS
We conclude that the MEP amplitude ratio may be useful to predict functional status of the extremities in patients who suffered stroke.
Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea.
Gi-Wook
GW
Kim
Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea. ; Research Institute of Clinical Medicine of Chonbuk National University and Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea.
Yu Hui
YH
Won
Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea. ; Research Institute of Clinical Medicine of Chonbuk National University and Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea.
Sung-Hee
SH
Park
Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea. ; Research Institute of Clinical Medicine of Chonbuk National University and Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea.
Jeong-Hwan
JH
Seo
Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea. ; Research Institute of Clinical Medicine of Chonbuk National University and Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea.
Myoung-Hwan
MH
Ko
Activities of daily living; Motor evoked potentials; Motor skills; Muscle strength; Stroke