Carlos E. Davila, Electrical Engineering Dept. Southern Methodist University

Biomedical Instrumentation

Electrophysiology (ENG-EMG)

Electroneurogram (ENG)

• Measured by stimulating a peripheral nerve with electric shock.

• Nerve response along nerve periphery is then measured.

• Can be used to determine nerve conduction velocity:

5

ENG (cont.)

+ _

vo

stimulate ulnar nerve

hypothenar muscle

biphasic

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ENG(cont.)

0 10 20 30 40 50

10 6 2

10 6 2

mV

ms

L

Rpeak amplitude

RL

latency

right ulnar neuropathy in elbow (Aminoff)

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Electromyogram (EMG)

signal generated by muscle cells amplitude: 0.1-5 mV freq range: 0-10,00 Hz measurement: needle electrodes single motor unit (SMU): smallest area of muscle

tissue that can be activated by a volitional effort SMU generates a triphasic potential having a

amplitude of 20-2000 V lasting 3-15 ms. Firing rate of SMU 6-30 per second.

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Electromyogram (EMG) Recruitment

SMU SMU SMUSMU SMU

contraction effort

can’t distinguish individual SMU’s

interference pattern

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EMG Affected by Disease

In neuropathy, diseased nerves degenerate, then regenerate.

Regenerated nerves conduct more slowly than healthy ones.

This produces a desynchronization in the EMG pattern.

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Evoked EMG Measurements/ENG

+ _

vo

stimulate ulnar nerve

hypothenar musclehealthy

pathology

10 ms