Electromyography Course Outline

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Questions and Answers

What type of electrodes are used in intramuscular electromyography (nEMG)?

Cable electrodes

Surface electrodes

Needle electrodes (correct)

Wireless electrodes

Which of the following is an application of nerve conduction studies (NCS)?

Assessing joint mobility

Classifying muscle strains

Measuring blood circulation

Determining axonal degeneration (correct)

During the procedure of electromyography, what does the neurologist instruct the patient to do?

Move the limb continuously

Apply pressure to the electrode

Sleep to relax the muscle

Contract and rest the muscle (correct)

What type of muscle response does surface electromyography (sEMG) record?

Electrical activity without insertion Signup and view all the answers

What is the main purpose of electromyography?

To analyze electrical activity in muscles Signup and view all the answers

Which of the following factors can influence the results of nerve conduction studies?

Temperature of the skin Signup and view all the answers

Which condition can electromyography help differentiate between?

Neuropathy and myopathy Signup and view all the answers

What happens to the needle electrode during an electromyography procedure?

It records muscle activity during rest and movement Signup and view all the answers

What does an EMG primarily measure in muscles?

Electrical activity of muscle motor units Signup and view all the answers

What is one primary use of electromyography (EMG)?

To detect neuromuscular abnormalities Signup and view all the answers

What disadvantage does surface electromyography (sEMG) have compared to invasive methods?

It is more prone to artifacts in reading Signup and view all the answers

What does the conduction velocity (CV) in an EMG report describe?

The speed at which electrical impulse travels along the nerve Signup and view all the answers

Which of the following parameters is NOT recorded in an EMG/NCS report?

Speed of muscle contraction Signup and view all the answers

What characterizes the F wave in EMG analysis?

It is an electrical echo indicating conduction along the motor nerve Signup and view all the answers

What is the primary function of the recording electrodes in an EMG setup?

To place over the muscle and measure electrical activity Signup and view all the answers

What aspect of an electrical wave does the amplitude parameter in an EMG report indicate?

The height of the signal wave Signup and view all the answers

What characterizes the H reflex in relation to leg movement?

An impulse travels to the spinal cord via a sensory nerve. Signup and view all the answers

In individuals with myopathy, what happens to the muscle fiber recruitment during voluntary activity?

Full recruitment occurs despite individual motor units generating less tension. Signup and view all the answers

What is a defining feature of the potential generated in myopathy?

Short-duration, low-amplitude polyphasic potential. Signup and view all the answers

What is the typical duration range of normal motor unit action potentials (MUAPs)?

2-15 msec Signup and view all the answers

Which type of potential indicates neuropathic conditions?

Long-duration, high-amplitude polyphasic potential. Signup and view all the answers

What is the effect of decreased muscle fibers in individual motor units for myopathy?

Short-duration recruitment of muscle fibers. Signup and view all the answers

What type of motor unit action potential is characterized as biphasic or triphasic?

Normal MUAPs Signup and view all the answers

What is the primary reason for the low amplitude observed in myopathic potentials?

Decreased recruitment from muscle fibers Signup and view all the answers

What is the significance of polyphasic potentials with more than 4 phases in an EMG analysis?

They are considered nonspecific findings. Signup and view all the answers

What is a typical EMG finding associated with neurogenic conditions?

Decreased number of motor units. Signup and view all the answers

Why do surviving axons increase the number of muscle fibers they innervate after reinnervation?

To compensate for the loss of motor units. Signup and view all the answers

What characteristic is commonly seen in neuropathic EMGs regarding the amplitude of potentials?

High amplitude is indicative of motor unit recruitment. Signup and view all the answers

What physiological changes are observed in motor units during voluntary activity in case of neuropathy?

Compensatory increase in firing rates of remaining units. Signup and view all the answers

What leads to a long duration in neuropathic potentials?

Difficulty in transmission of impulses to muscle or motor unit. Signup and view all the answers

Which of the following reflects an increase in excitation in the context of reinnervation?

Increased amplitude and excitation. Signup and view all the answers

What percentage of normal muscles might show small amounts of polyphasic potentials?

10-15% Signup and view all the answers

Study Notes

Electromyography Overview

Electromyography (EMG) measures electrical activity in muscles, reflecting muscle response to nerve stimulation.
Neurophysiological technique assesses skeletal muscle activity to identify neuromuscular disorders.

Types of Electromyography

Surface Electromyography (sEMG):
- Non-invasive, uses adhesive electrodes on the skin.
- Provides time/intensity data of superficial muscle activation; advantages include broader coverage but is more prone to artifacts.
Intramuscular Electromyography (nEMG):
- Invasive method where a needle electrode is inserted directly into the muscle to record electrical activity.
Nerve Conduction Study (NCS):
- Evaluates signal speed and strength between nerve points, crucial in diagnosing neuropathies related to axonal degeneration or demyelination.

Procedures

Needle electrode is inserted into the muscle under neurologist guidance for contraction and rest testing.
Captures muscle activity in both resting and active states.

EMG/NCS Parameters

Amplitude: Height of electrical wave signal.
Conduction Velocity (CV): Speed at which electrical impulses travel along nerves.
Duration: Width of an electrical wave.
Conduction Block: Reduction of signal across anatomical regions.
F Wave: Electrical echo indicating conduction along a motor nerve.
H Reflex: Represents sensory nerve impulse travel to the spinal cord and back through motor nerves.

Clinical Correlations

Myopathy:
- Characterized by fewer muscle fibers per motor unit but normal overall motor unit count.
- Features include full recruitment of weaker muscles and short-duration, low-amplitude polyphasic potentials due to limited muscle fiber activation.
Neuropathy:
- Reveals decreased motor unit count and recruitment; low action potential transmission leads to compensatory increased firing rates of remaining units.
- Results in long-duration, high-amplitude polyphasic potentials reflecting difficulties in impulse transmission and increased fiber recruitment after reinnervation.

Key Points

EMG is vital for detecting and evaluating neuromuscular abnormalities.
Understanding EMG parameters aids in diagnosing conditions affecting muscle and nerve function.
Distinguishing between myopathy and neuropathy is crucial for correct treatment strategies.

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Description

This quiz covers the fundamentals of electromyography (nEMG), including the definition and uses of needle electrodes. It provides insights into the techniques of measuring electrical activity in muscles through invasive electrode methods. Test your knowledge on this essential topic in medical diagnostics.