A Novel Analysis of Compound Muscle Action Potential Scan: Staircase Function Fitting and StairFit Motor Unit Number Estimation

IEEE J Biomed Health Inform., 2023 · DOI: 10.1109/jbhi.2022.3229211 · Published: March 1, 2023

Simple Explanation

The study introduces a new method to analyze CMAP scans, which are detailed recordings of muscle response to nerve stimulation. This method uses a staircase function to model the CMAP scan, estimating the number of motor units and their properties. The core idea is that a CMAP scan, ideally, should resemble a staircase pattern, with each step representing the activation of a motor unit. The algorithm finds the best-fitting staircase function to the CMAP scan data. This approach provides an estimation of motor unit number (MUNE) along with spike amplitude and activation threshold of each motor unit, which are useful for diagnosing neuromuscular diseases.

Study Duration

Not specified

Participants

13 SCI tetraplegia, 13 neurologically intact

Evidence Level

Not specified

Key Findings

1
The staircase function fitting provides an appropriate approach to CMAP scan processing, yielding MUNE and other useful parameters for examination of motor unit loss and muscle fiber reinnervation.
2
The average MUNE of the first dorsal interosseous muscle derived from the staircase function fitting was 57.5 ± 26.9 for the SCI subjects, which was significantly lower than 101.2 ± 16.9, derived from the control group (p < 0.001).
3
Simulation results confirmed the significance of the staircase function fit regarding MUNE performance, repeatability, and test-retest reliability.

Research Summary

This study introduces a novel CMAP scan analysis method using staircase function fitting to extract MUNE and other physiological information. The staircase fitting model was validated using simulated CMAP scan data and experimental data from healthy control and spinal cord injury (SCI) subjects. Results indicate the method can effectively estimate motor unit number and identify motor unit loss and muscle fiber reinnervation.

Practical Implications

Clinical Diagnosis

The StairFit MUNE method can be used as a tool for early diagnosis and tracking of neuromuscular diseases such as ALS.

Rehabilitation Monitoring

The method can be applied to monitor the progress of muscle reinnervation and motor unit recovery in patients undergoing rehabilitation after SCI or other neurological injuries.

Electrophysiological Research

The staircase function fitting provides a detailed analysis of CMAP scans, allowing for a better understanding of motor unit physiology and neuromuscular function.

Study Limitations

1
The accuracy of MUNE depends on the assumption that all motor units are activated simultaneously and generate effective CMAP amplitude gains above the noise level.
2
The error threshold for StairFit MUNE was fixed to be 15 μV, which may not be optimal for all experimental conditions.
3
The study only focused on the first dorsal interosseous muscle; further research is needed to validate the method on other muscles.

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