Related Experiment Video
Updated: May 22, 2026

In Vivo Electrophysiological Measurement of Compound Muscle Action Potential from the Forelimbs in Mouse Models of Motor Neuron Degeneration
Published on: June 15, 2018
Correlation between compound muscle action potential amplitude and duration in axonal and demyelinating
Hatice Tankisi1, Marit Otto, Kirsten Pugdahl
1Department of Clinical Neurophysiology, Aarhus University Hospital, DK - 8000 Aarhus, Denmark.
Objective:
To get a better understanding of pathophysiology in polyneuropathies (PNPs) by correlating compound muscle action potential (CMAP) amplitude with duration.
Methods:
A total of 145 motor nerve conduction studies (MNCS) in 53 axonal and 132 MNCS in 45 demyelinating PNPs were analyzed. Peroneal and tibial MNCS were done by surface stimulation while for median and ulnar nerves near nerve or surface stimulations were used. CMAP amplitude and duration were compared in axonal and demyelination PNPs. Relationships between amplitude and duration of distally and proximally evoked CMAP were examined using regression analysis.
Results:
CMAP amplitude was lower and duration was increased in all examined nerves in demyelinating PNPs than in axonal PNPs. In demyelinating PNPs, an inverse linear correlation between amplitude and duration was seen in distally and proximally evoked CMAP in all examined nerves. In axonal PNPs, there was no correlation in any of the nerves neither in distally nor in proximally evoked CMAP.
Conclusions:
Distal CMAP duration and the relationship between CMAP amplitude and duration show supplementary electrodiagnostic potential in demyelinating PNPs.
Significance:
More knowledge about the relation between amplitude and duration in axonal lesions and demyelination may help to reveal the pathophysiology in PNPs. Significant correlation between amplitude and duration in demyelination may suggest that the severe decrease in amplitude in demyelinating PNPs is probably due to the increase in duration secondary to temporal dispersion.
Related Concept Videos
Generation of Action Potential in Skeletal Muscles
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Action Potentials
Alterations in Muscle Tone lll
Local Anesthetics: Differential Sensitivity of Nerve Fibers
Action Potential
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Action Potential
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...

