Two motor units

Rat tibialis anterior muscle after single axon stimulation. PAS

Motor Unit Potential (MUP)Motor Unit Potential (MUP)

7 Turns3 Phases6 Segments

Amplitude Phase

Duration

Rising Time

Satellite

Turns

Baseline Crossing

Segment

Single Potential, Phases < 4 Polyphasic Potential, Phases > 4

Uptake area of concentric electrode

EMG TestsEMG Tests

� Insertion activity

� Activity at rest

� MUP analysis

� Interference pattern

� Turn/ Amplitude analysis

Muscular ContractionMuscular ContractionStriated MusclePeripheral Nerve

No

Contraction

Discrete

Contraction

Moderate

Contraction

Maximum

Contraction

Motor Neuron

Motor Unit

0 MUP

1 MUP

3 MUPs

++ MUPs

Motor Unit Potentials

Needle Insertion - Activity at restNeedle Insertion - Activity at rest

Fibrillation PotentialPartial denervation, Myopathy,

Polymyositis.Amplitude: 100 - 200 µV

Activity at rest - no potential

Muscle

Orientation

marker

Needle

Fibers orientation

15°

ElectromyographyElectromyography

Concentric Needle

or

Monopolar Needle

Striated Muscle

Motor Unit

1

2

Recruitment EMG

Motor Unit Potentials

(1) and (2)

100 ms

20 ms

5 ms 1 2

• Moderate contraction

Single - TriggeringManual Selection - Raster

M U P AnalysisM U P Analysis

MUP Algorithm recognitionMulti-MUP - Averaging

Manual Selection - RasterManual Selection - RasterMUP Algorithm recognition

Multi-MUP - AveragingMUP Algorithm recognition

Multi-MUP - Averaging

• Simple/ polyphasic potentials ratio• Amplitude• Duration

Single - TriggeringSingle - Triggering

AveragingAveraging

�

AveragingAveraging

MUPs summary

Muscular dystrophy

Type grouping

DCN EMG

MAXIMUM EFFORT

EMG Needles:

- Disposable concentric

- Disposable monopolar

Auditory control of:

- Resting silence

- Sound of MUPs

- Frequency firing

EMG - Recruitment Interference

Pattern

EMG - Recruitment Interference

Pattern

< 50 ms ( 20 Hz )

Amplitude depends on Muscle, 4-2 mV

�

Turns/ AmplitudeTurns/ Amplitude

• 1 second EMG signal

• Concentric or Monopolar Needle

• Few sites in same muscle

• 20 measurements at diff. force

• Number of Turns > 100 µV

• Mean Turns Amplitude

T1

T2

T3

T4

T5

S1S2

S3S4

A4

A2

A1A3

Change in signal direction = Turn Segment Amplitude > 100 µV

A = AmplitudeS = Segment

Myopathy

Neuropathy

Polymyositis

tib ant

Polio Sequele

tib ant

Amplitude

Turns

Amplitude

Turns

Short Segments / Amplitude / ActivityShort Segments / Amplitude / Activity

Myopathy

Neuropathy

Sum of activity periodsin % (or ms) of full IP

NSS Amplitude Duration

Yes < 0.5 mV < 1.5 msYes 0.5 > < 2mV < 3 ms No > 2 mV < 5 ms

• 500 ms EMG signal then x 2

• NSS Number of Small Segments

• UCA Upper Centile Amplitude

Small Segment

Activity

Normal turn/amplitude analysis Normal activity/envelope

Turn-amp and

activity-envelope

analyses in

myopathy

Turn-amp and activity-

envelope analyses in

neurogenic conditions

Pathologies in Striated MusclePathologies in Striated Muscle

Normal

Neuropathy

Myopathy

Myasthenia

CNEMG

Same effort, same muscle,

different pathologies

Ground

�Neuromuscular junction

disease. See DecrementUnstable MUPs