ELECTROMYOGRAPHY

ELECTROMYOGRAPHY

1. DR NILESH KATE
MBBS,MD
PROFESSOR
DEPT. OF PHYSIOLOGY
ELECTRO-MYO-
GRAPHY

2. Objectives.
Def –Electromyography, electromyograph,
electromyogram
How it is done
Applications
Abnormal patterns.
Tuesday, December 6, 2022

3. ELECTROMYOGRAPHY
A technique of
recording of total
electrical activity of
the motor nerve and
the muscle under
study. (Motor UNIT)
Tuesday, December 6, 2022

4. Important terms
Electromyography–
technique
Electromyograph–A
machine used to
record a graph.
Electromyogram–A
record obtained
(graph)
Tuesday, December 6, 2022

5. Instrument used.
Cathod ray
oscilloscope –
Why not
galvanometer –
needle made up of
metal –metal having
mass –inertia –so
cannot measure fine
fluctuations in mv
Tuesday, December 6, 2022

6. Electrodes
Surface electrodes –
metal disc
Needle electrodes –
hypodermic needle
Advantages
Disadvantages
Amplifier
Monitor
Tuesday, December 6, 2022

7. Tuesday, December 6, 2022

8. Recording of EMG
During rest –little
activity
Then subject asked to
contract muscle
slightly –record –then
asked to contract
more
Tuesday, December 6, 2022

9. Tuesday, December 6, 2022
Sr no Pattern of EMG Recorded Findings
1 Resting activity Muscle relaxed No activity (Basal
Activity)
2 Insertion Activity Due to movement of
needle within insertion
tract..
Brief action
potential.
3 Motor Unit PotentialSlight reading due to
contraction of few motor
units
A few motor unit
AP, biphasic or
triphasic, short
duration
4 Recruitment Progressive stronger
muscle contraction
Increase no of
contraction -
interference

10. Tuesday, December 6, 2022

11. Effect
Muscle contraction.
frequency of nerve
impulse to motor unit
no of contracting
motor units.
Tuesday, December 6, 2022

12. Motor units
The motor neuron &
muscle fiber supplied
by it.
Tuesday, December 6, 2022

13. Motor units
Back muscle
Each nerve fiber
supplies many muscle
fibers (100-200)
Gross movements
Extraocular muscles
Each nerve fiber
supplies few muscle
fibers (3-6)
Fine movements..
Tuesday, December 6, 2022

14. Types of muscle contractions
Muscle fasciculations
Visible to naked eye
Only seen in
neurogenic disease
Muscle fibrillations
Not visible to naked eye
Seen in neurogenic &
myogenic disease..
So………to find out
fibrillations we perform
EMG……
Tuesday, December 6, 2022

15. NORMAL EMG
During Rest
Almost no activity…
Tuesday, December 6, 2022

16. NORMAL EMG
With increase force of
contractions.
Recruitments of more
motor units
Why different shapes
Using different motor
units..
Tuesday, December 6, 2022

17. NORMAL EMG
Amplitude
Represents no of
muscle fibers within
the unit.
Tuesday, December 6, 2022

18. Normal EMG
With fully contracted
(Active) muscle –
overlap &
interference..
Tuesday, December 6, 2022

19. Motor unit potential
The sum of action
potential produced in
the muscle fiber
stimulated by single
motor neuron
Characterized by
duration, phases,
amplitude..
Tuesday, December 6, 2022

20. Factors affecting motor unit
potential
Technical factors
Type of electrode
Characteristics of recording muscle
Electrical characteristics of cable
Preamplifier & amplifier
Method of recording.
Tuesday, December 6, 2022

21. Factors affecting motor unit
potential
Physiological factors.
Age of the patients
Muscle examined
Temperature
Tuesday, December 6, 2022

22. Analysis of EMG
Qualitative
Visual inspection of
record.
Quantitative
Amplitude
Duration
Frequency
Power spectrum
analysis
Tuesday, December 6, 2022

23. Clinical
application of
EMG
Tuesday, December 6, 2022

24. Difference in types of diseases
Neurogenic disease.
Problem in nerve fibre
no of motor units.(but
surviving ones are bigger)
Denervated muscle may
become supplied by
surviving neurons
Fasciculations (visible)
Fibrillations (invisible)
Myopathies.
Problem in muscle fiber
 size of motor units
Fibrillations
Tuesday, December 6, 2022

25. EMG IN
DIFFERENT
DISEASES.
Tuesday, December 6, 2022

26. Neurogenic
disease
Myopathies (MG)
During rest – spontaneous
activity (due to loss
of inhibition)
No activity
With increase force
of contraction -
no of motor
units, but surviving
ones are bigger
BIGGER
AMPLITUDE
Size of motor
units
amplitude &
durations
Maximum
contraction
interference
pattern
amplitude,
duration &
interference
Tuesday, December 6, 2022

27. Applications of EMG
Kinesiology–to assess degree and sequence
of contraction of muscles in a movements
Gradingthe force of muscular contraction
Clinical diagnosis & follow up of
neurogenic & myopathic diseases.
Tuesday, December 6, 2022

28. Thank
You