This document discusses quantitative electromyography (QEMG) and what can be assessed using EMG. It outlines various muscle fiber characteristics and motor unit organization that EMG can evaluate, including number of fibers, grouping, and transmission at the neuromuscular junction. Parameters that can be quantified from concentric and monopolar EMG signals are described, such as spontaneous activity, motor unit potential (MUP) shape, recruitment, and dynamic changes over time. Various MUP parameters that provide information on motor unit size and characteristics are also defined. The document compares these parameters in evaluating different muscle disorders like neuropathy, myopathy and provides examples of quantitative analyses.
2. What can we assess with EMG?What can we assess with EMG?
• Muscle membrane function - spontaneous
• Muscle fibre characteristics; diameter
• MU organization
– number of fibers
– grouping
• N-M transmission
• Motor units
– total number
– activation; pattern, fullness Stålberg
3. Parameters to quantify inParameters to quantify in
Conc/Monopolar EMGConc/Monopolar EMG
• spontaneous activityspontaneous activity
• shape of individual MUPsshape of individual MUPs
• jigglejiggle
• recruitment (recruitment (early, reducedearly, reduced))
• fullness at strong activationfullness at strong activation
• dynamic changes with time (dynamic changes with time (fatiguefatigue))
4.
5. Spontaneous activity in normal
• insertional activity
• end-plate noise
• ”nerve spikes”
• positive wave at end-plate zone
13. Parameters used in MUPParameters used in MUP
analysisanalysis
parameterparameter significancesignificance measurementmeasurement
• Amplitude # fibers/0.5mm peak-peak
• Area # fibers/2 mm within dur
• Duration # fibers in 2.5 mm slope criteria
• Thickness # close fibre area/ampl
• Size index MU size normalized thickness
• Phases temp dispersion 0-cross + 1
• Turns “ change in dir
• Irregularity “ length/ampl
• Rise time closeness to fibre neg-pos peak
• Satellites extreme delay late spike
• Jiggle n-m transm shape stability
Stålberg
14. Parameters that can be assessedParameters that can be assessed visually/manuallyvisually/manually
parameterparameter significancesignificance measurementmeasurement
• Amplitude # fibers/0.5mm peak-peak
• area # fibers/2 mm within dur
• Duration # fibers in 2.5 mm slope criteria
• Thickness # close fibre area/ampl
• Size index MU size normalized thickness
• Phases temp dispersion 0-cross + 1
• Turns “ change in dir
• Irregularity “ length/ampl
• Rise time closeness to fibre neg-pos peak
• Satellites extreme delay late spike
• Jiggle n-m transm shape stability
Stålberg
15.
16. This example: Multi MUP analysis
techniques to decompose a mixed signal into its constituentstechniques to decompose a mixed signal into its constituents
Decomposition;Decomposition;
Stålberg
45. Reference values
necessary to separate abnormal from normal
This is a crucial point in quantitative EMG analysis
• mean, SD (# of SDs = Z-score)
• median, percentiles
• outliers
• combine different data (multivariate analysis, index)
A few examples
50. Onset frequency
= freq of a MUP when recruited
Recruitment frequency
= freq. of 1st
MU when 2nd
is recruited
neuropathy ↑
myopathies ↓
Recruitment ratio (slight contraction)
= # discharges/# active MUs
51. Onset freq = 6 Hz
Recruitment freq = 9Hz
Recruitment ratio 20/4=5
Interference
6 8 10 12 14 16 18 20 Hz
normal
MU 1
MU 2
MU 3
MU 4
MU 5
52. Onset freq = 6 Hz
Recruitment freq = 9Hz
Recruitment ratio 20/4=5
Interference
6 8 10 12 14 16 18 20 Hz
normal
MU 1
MU 2
MU 3
MU 4
MU 5
53. Onset freq = 6 Hz
Recruitment freq = 9Hz
Recruitment ratio 20/4=5
Interference
6 8 10 12 14 16 18 20 Hz
normal
MU 1
MU 2
MU 3
MU 4
MU 5
54. 6 8 10 12 14 16 18 20 Hz
Onset= 6 Hz
Recruitment freq = 12
Recruitment ratio = 18/3=6
neurogenic
MU 1
(MU 2)
MU 3
MU 4
55. 6 8 10 12 14 16 18 20 Hz
Onset= 6 Hz
Recruitment freq = 7Hz
Recruit ratio = 10/3=3
myopathy
MU 1
MU 2
MU 3
MU 4
64. How to quantitateHow to quantitate
Central driveCentral drive
Parameters:
• pattern - firing rate, onset frequency
• fullness - RMS, integration, “activity”
• stim/voluntary difference
– CMAP vs. RMS of voluntary EMG
– superimposed twitch
Stålberg
65. Comparison of electrophysiological parameters
Parameters nm-j myopathy den/reinn axon loss CB central
SFEMG n n n
Conv MUP abn n n n
Conv IP n myo neur
Macro n n n n n
MUNE n n n n n
TMS n n n abn
66. Reasons for performing QEMG
• standardized way of measuring
• improved sensitivity
• results can be transferred
– from one time to the other - follow up
– from one physician to the other
– from on lab to the other
• reliable results also from less experienced
EMGers
• good during training