Podcast
Questions and Answers
What type of electrodes are used in intramuscular electromyography (nEMG)?
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)?
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?
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?
What type of muscle response does surface electromyography (sEMG) record?
What is the main purpose of electromyography?
What is the main purpose of electromyography?
Which of the following factors can influence the results of nerve conduction studies?
Which of the following factors can influence the results of nerve conduction studies?
Which condition can electromyography help differentiate between?
Which condition can electromyography help differentiate between?
What happens to the needle electrode during an electromyography procedure?
What happens to the needle electrode during an electromyography procedure?
What does an EMG primarily measure in muscles?
What does an EMG primarily measure in muscles?
What is one primary use of electromyography (EMG)?
What is one primary use of electromyography (EMG)?
What disadvantage does surface electromyography (sEMG) have compared to invasive methods?
What disadvantage does surface electromyography (sEMG) have compared to invasive methods?
What does the conduction velocity (CV) in an EMG report describe?
What does the conduction velocity (CV) in an EMG report describe?
Which of the following parameters is NOT recorded in an EMG/NCS report?
Which of the following parameters is NOT recorded in an EMG/NCS report?
What characterizes the F wave in EMG analysis?
What characterizes the F wave in EMG analysis?
What is the primary function of the recording electrodes in an EMG setup?
What is the primary function of the recording electrodes in an EMG setup?
What aspect of an electrical wave does the amplitude parameter in an EMG report indicate?
What aspect of an electrical wave does the amplitude parameter in an EMG report indicate?
What characterizes the H reflex in relation to leg movement?
What characterizes the H reflex in relation to leg movement?
In individuals with myopathy, what happens to the muscle fiber recruitment during voluntary activity?
In individuals with myopathy, what happens to the muscle fiber recruitment during voluntary activity?
What is a defining feature of the potential generated in myopathy?
What is a defining feature of the potential generated in myopathy?
What is the typical duration range of normal motor unit action potentials (MUAPs)?
What is the typical duration range of normal motor unit action potentials (MUAPs)?
Which type of potential indicates neuropathic conditions?
Which type of potential indicates neuropathic conditions?
What is the effect of decreased muscle fibers in individual motor units for myopathy?
What is the effect of decreased muscle fibers in individual motor units for myopathy?
What type of motor unit action potential is characterized as biphasic or triphasic?
What type of motor unit action potential is characterized as biphasic or triphasic?
What is the primary reason for the low amplitude observed in myopathic potentials?
What is the primary reason for the low amplitude observed in myopathic potentials?
What is the significance of polyphasic potentials with more than 4 phases in an EMG analysis?
What is the significance of polyphasic potentials with more than 4 phases in an EMG analysis?
What is a typical EMG finding associated with neurogenic conditions?
What is a typical EMG finding associated with neurogenic conditions?
Why do surviving axons increase the number of muscle fibers they innervate after reinnervation?
Why do surviving axons increase the number of muscle fibers they innervate after reinnervation?
What characteristic is commonly seen in neuropathic EMGs regarding the amplitude of potentials?
What characteristic is commonly seen in neuropathic EMGs regarding the amplitude of potentials?
What physiological changes are observed in motor units during voluntary activity in case of neuropathy?
What physiological changes are observed in motor units during voluntary activity in case of neuropathy?
What leads to a long duration in neuropathic potentials?
What leads to a long duration in neuropathic potentials?
Which of the following reflects an increase in excitation in the context of reinnervation?
Which of the following reflects an increase in excitation in the context of reinnervation?
What percentage of normal muscles might show small amounts of polyphasic potentials?
What percentage of normal muscles might show small amounts of polyphasic potentials?
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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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