Podcast
Questions and Answers
What is a characteristic of polyphasic potentials in electromyography?
What is a characteristic of polyphasic potentials in electromyography?
- Are always indicative of muscle damage
- Can be found in small percentages in normal muscles (correct)
- Are specific to myogenic diseases
- Only occur in neurogenic diseases
What is a consequence of decreased number of motor units in neuropathy?
What is a consequence of decreased number of motor units in neuropathy?
- Enhanced firing rate of all motor units
- Increased conduction velocity of impulses
- Reduced recruitment density and overall recruitment (correct)
- Increased overall action potential transmission
What occurs after the process of reinnervation in motor units?
What occurs after the process of reinnervation in motor units?
- The number of muscle fibers per unit decreases
- Surviving axons branch to innervate more muscle fibers (correct)
- Surviving axons degenerate further
- Adjacent muscle fibers are no longer innervated
What is the primary purpose of intramuscular electromyography (nEMG)?
What is the primary purpose of intramuscular electromyography (nEMG)?
What leads to the high amplitude observed in neuropathic potentials?
What leads to the high amplitude observed in neuropathic potentials?
What is the primary cause of long-duration potentials in neuropathic EMG?
What is the primary cause of long-duration potentials in neuropathic EMG?
Which type of electromyography involves the use of electrode stickers applied to the skin?
Which type of electromyography involves the use of electrode stickers applied to the skin?
Which of the following is a nonspecific finding in electromyography?
Which of the following is a nonspecific finding in electromyography?
In the context of electromyography, what does the procedure typically involve?
In the context of electromyography, what does the procedure typically involve?
What happens to the firing rate of surviving motor units during voluntary activity in neuropathy?
What happens to the firing rate of surviving motor units during voluntary activity in neuropathy?
What are the two types of dysfunctions compared in the clinical correlation of electromyography?
What are the two types of dysfunctions compared in the clinical correlation of electromyography?
What does a nerve conduction study (NCS) primarily measure?
What does a nerve conduction study (NCS) primarily measure?
Which of the following best describes the relationship between amplitude and excitation in motor units post-reinnervation?
Which of the following best describes the relationship between amplitude and excitation in motor units post-reinnervation?
During intramuscular electromyography, when is the needle electrode typically recording muscle activity?
During intramuscular electromyography, when is the needle electrode typically recording muscle activity?
What do surface electrodes in a nerve conduction study help classify?
What do surface electrodes in a nerve conduction study help classify?
What is one of the implications of a fracture in the upper arm bone related to nerve function?
What is one of the implications of a fracture in the upper arm bone related to nerve function?
What does the electrical activity detected during rest in an EMG indicate?
What does the electrical activity detected during rest in an EMG indicate?
Which parameter in an EMG report describes the height of the electrical signal waveform?
Which parameter in an EMG report describes the height of the electrical signal waveform?
What is the primary advantage of surface electromyography (sEMG) over needle electromyography (nEMG)?
What is the primary advantage of surface electromyography (sEMG) over needle electromyography (nEMG)?
What does a conduction block in an EMG report signify?
What does a conduction block in an EMG report signify?
What is the purpose of the F wave in an electromyography study?
What is the purpose of the F wave in an electromyography study?
What type of electrode configuration is typically used in surface electromyography (sEMG)?
What type of electrode configuration is typically used in surface electromyography (sEMG)?
In the context of nerve conduction studies, what does conduction velocity (CV) measure?
In the context of nerve conduction studies, what does conduction velocity (CV) measure?
What should be done if nerve function does not return after 4 months of injury, according to EMG practices?
What should be done if nerve function does not return after 4 months of injury, according to EMG practices?
What characterizes the H reflex in terms of its wave type?
What characterizes the H reflex in terms of its wave type?
In myopathy, how does the recruitment of motor units typically occur?
In myopathy, how does the recruitment of motor units typically occur?
What is the expected amplitude of polyphasic potentials in myopathy?
What is the expected amplitude of polyphasic potentials in myopathy?
What is a primary feature of the motor unit action potential (MUAP) duration in normal conditions?
What is a primary feature of the motor unit action potential (MUAP) duration in normal conditions?
How is the recruitment density affected in myopathy?
How is the recruitment density affected in myopathy?
What happens to the duration of polyphasic potentials in myopathic conditions?
What happens to the duration of polyphasic potentials in myopathic conditions?
What defines the nature of the impulse in the H reflex?
What defines the nature of the impulse in the H reflex?
What type of potential can indicate neuropathic conditions?
What type of potential can indicate neuropathic conditions?
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 basics of electromyography (EMG) focusing on the use of invasive needle electrodes. It explores the definition, uses, and the principles behind recording electrical activity in muscles. Perfect for those studying neuromuscular physiology.
