1. Fundamentals of Nerve
Conduction Studies & EMG

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3. Nerve Conduction Studies
A medical test where peripheral nerves are
electrically stimulated and responses are
recorded over nerve or muscle

4. Nerve Conduction Studies include
1) Routine Studies
A) Motor nerve conduction
B) Sensory nerve conduction
C) Late responses
2) Special Studies
Repetitive Stimulation, SSEP, MEP, VEP

5. Motor nerve conduction studies
1. Electrodes placed over muscle
2. Supra maximal stimulus applied over
nerve to muscle
3. Compound motor action potential
recorded (CMAP)

7. Motor nerve conduction studies
1. Stimulus repeated at second site
2. Second CMAP recorded
3. Distance measured between stimulation
sites (cm)

9. Data reported for motor studies:
1. Distal latency
2. Amplitude of CMAP (each site)
3. Conduction velocity between sites
(calculated)
Data compared to normal data and
interpretation provided

14. Sensory nerve conduction studies
1. Electrode placed over sensory cutaneous
branch of nerve
2. Stimulus applied to nerve
3. Sensory nerve action potential recorded
(SNAP)

18. Late responses: F-waves
1. F-waves results from small number of motor
neurons activated by antidromic
(back-firing)
2. Variable in amplitude and latency
3. Commonly minimum latency is measured
4.Supra maximal stimulus are applied

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22. NCS: limitations
1. Painful stimulations
2. Temperature sensitive (S>M)
3. Assess mainly large fibers
4. Most useful for nerve conditions

23. Electromyography
Definition: A medical test where electrical
impulses are recorded from muscle at rest
and while contracting.
The recording is made by
1. needle – from a needle inserted in the
selected muscle
2. surface – from an electrode placed on the
skin over the selected muscle

25. Electromyography
1. Motor neuron or nerve diseases cause
larger units firing rapidly
2. muscle disorders give rise to smaller
MUPs that fire early

28. NCS: Diagnostic Utility
1. Nerve diseases
2. Nerve root disease
3. Muscle disorders
4. Neuromuscular Junction disorder

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