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Multipoint incremental motor unit number estimation as an outcome measure in ALS
J M Shefner1, M L Watson, L Simionescu
1Department of Neurology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA. shefnerj@upstate.edu
Neurology
|June 17, 2011
Summary
This study shows that a modified Motor Unit Number Estimation (MUNE) method is a reliable outcome measure for amyotrophic lateral sclerosis (ALS) clinical trials. The new MUNE technique demonstrated good repeatability and significant motor unit loss over time in ALS patients.
Area of Science:
- Neurology
- Clinical Electrophysiology
- Biomedical Engineering
Background:
- Amyotrophic lateral sclerosis (ALS) clinical trials require improved outcome measures to increase statistical power.
- Motor Unit Number Estimation (MUNE) is a promising tool, but previous methods suffered from high variability and artifacts in multicenter settings.
- A modified MUNE approach was investigated to address these limitations.
Purpose of the Study:
- To assess the efficacy of a modified incremental Motor Unit Number Estimation (MUNE) technique.
- To evaluate MUNE as a reliable outcome measure in a multicenter natural history study of amyotrophic lateral sclerosis (ALS).
Main Methods:
- A modified multipoint incremental MUNE was applied to 50 healthy subjects and 71 ALS patients over 500 days.
- Nerves were stimulated at three locations with three increments each.
- Motor Unit Number Estimation (MUNE) was calculated using average single motor unit action potential (SMUP) amplitude and maximum compound muscle action potential (CMAP) amplitude.
Main Results:
- The test-retest variability of the modified MUNE was 9% in healthy subjects.
- ALS patients exhibited a significant decline in MUNE, averaging approximately 9% per month.
- Single Motor Unit Action Potential (SMUP) amplitude changes over time were consistent with ALS pathophysiology.
Conclusions:
- The multipoint incremental MUNE method demonstrates favorable repeatability and sensitivity to motor unit loss in ALS.
- This modified MUNE technique is a viable and attractive outcome measure for ALS clinical trials and other motor neuron diseases.
- The method is practical, requiring standard EMG equipment and offering significant advantages over previously described MUNE techniques.
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