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Revised statistical motor unit number estimation in the Celecoxib/ALS trial
J M Shefner1, M E Cudkowicz, H Zhang
1Department of Neurology, SUNY Upstate Medical University, Syracuse, New York 13210, USA. shefnerj@upstate.edu
Muscle & Nerve
|October 24, 2006
Summary
Statistical motor unit number estimation (MUNE) may be unreliable for amyotrophic lateral sclerosis (ALS) due to motor unit instability. This method may not accurately reflect motor unit loss in diseases with variable motor unit responses.
Area of Science:
- Neurology
- Neurophysiology
Background:
- Amyotrophic lateral sclerosis (ALS) involves progressive motor unit loss, making motor unit number estimation (MUNE) a relevant assessment tool.
- Previous studies indicated statistical MUNE was reliable and reproducible in ALS clinical trials.
Purpose of the Study:
- To evaluate the appropriateness of statistical MUNE in assessing motor unit number in ALS.
- To investigate the impact of motor unit instability on MUNE accuracy.
Main Methods:
- Statistical MUNE was applied in a 12-month study of Celecoxib in ALS patients.
- Motor unit response variability to repeated stimuli was analyzed.
Main Results:
- MUNE declined by 49% over 12 months, but motor unit amplitude remained constant, suggesting a methodological artifact.
- Response variability in ALS patients was largely attributed to individual motor unit changes, not just the number of responding units.
Conclusions:
- The underlying assumption of statistical MUNE, that response variability solely reflects the number of responding motor units, is flawed in ALS.
- Statistical MUNE is not appropriate for diseases characterized by motor unit instability, such as ALS.
Related Concept Videos
00:46Motor Units
A motor unit consists of two main components: a single efferent motor neuron (i.e., a neuron that carries impulses away from the central nervous system) and all of the muscle fibers it innervates. The motor neuron may innervate multiple muscle fibers, which are single cells, but only one motor neuron innervates a single muscle fiber.
01:13Motor Units
The motor unit is a fundamental component of the neuromuscular system and plays a crucial role in coordinating muscle contractions. It consists of a somatic motor neuron, which connects and controls multiple skeletal muscle fibers, forming a single functional segment. The axon of the motor neuron branches out and establishes synaptic connections known as neuromuscular junctions with individual muscle fibers within the motor unit.
Motor units come in different sizes, with smaller units...
Motor units come in different sizes, with smaller units...