Insertional and Spontaneous EMG Activity Back to EMG main page

Volume II (Second Edition) : Atlas of EMG Waveforms
Chapters 2-4: Insertional and Spontaneous EMG Activity

Objectives
1 - Recognize normal insertional activity.
2 - Identify endplate noise, fibrillations, positive sharp waves, and fasciculations.
3 - Review "uncommon" waveforms of fibrillations and positive sharp waves.
4 - Demonstrate transformation from fibrillation to PSW and vice versa.
5 - Recognize and differentiate complex repetitive discharge, myotonia, neuromyotonia and myokymia.
6 - Observe Cramp Discharge
7 - Characterize extra discharges.

Insertional
Activity

Normal IA

Reduced IA

Increased IA
FIBs / PSWs

Waveforms

FIB = PSW

Unusual Configurations

Profused FIBs and PSWs

Pathophysiology

Interpretation
Endplate
Activity

Electrophysiology

Miniature Endplate Potentials

Endplate Spikes

Significance
Complex
Repetitive
Discharge

How it is generated

Ephaptic Transmission

Change in Configuration

Simple Iterative Discharge
Myotonic
Discharge

Waxing and Waning

Percussion Myotonia
Myokymic
Discharge

Continuous Pattern

Marching Band
Neuromyotonic
Discharge

The PING Sound

Associated with MUP
Cramp
Discharge

Resembles Interference Pattern

Fast Firing Motor Units
Extra
Discharge

Change in IDI

Multiplets
Fasciculations

Slow and Irregular Pattern

Single Motor Unit


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