Neurophysiology Flashcards
It affects the central and peripheral nervous system that is an autosomal disorder manifesting in early childhood. Sensorimotor neuropathy, corticospinal tract involvement with upper motor neuron signs, and optic atrophy leading to vision loss. The characteristic gait includes walking on the inner edges of the feet. The integument is also involved, and patients often have tightly curled hair. What is the diagnosis and gene involved?
Giant Axonal Neuropathy (GAN)
gigaxonin gene
What is accumulated in Refsum Disease?
Phytanic Acid
F-wave is obtained via
Supramaximal stimulation of a motor nerve
What are the 3 main measures of Sensory NCS?
Sensory Nerve Amplitude (SNAP) in microvolts
Sensory Latency (Onset and Peak)
Conduction Velocity
Definition of SNAP amplitude
SNAP amplitude (in microvolts) represents a measure of the number of axons conducting between the stimulation site and the recording site.
Definition of Sensory Latency.
Sensory latency (in milliseconds) is the time that it takes for the action potential to travel between the stimulation site and the recording site of the nerve.
What is the definition of conduction velocity?
The conduction velocity is measured in meters per second and is obtained by dividing the distance between the stimulation site and the recording site by the latency: Conduction velocity = Distance/Latency.
How is sensory NCS obtained?
It is obtained by stimulating a sensory nerve while recording the transmitted potential at a different site along the same nerve.
Compound Muscle Action is one of the resulting responses of motor CS. What does this interpret?
It depends on the motor axons transmitting the action potential, status of the neuromuscular junction, and muscle fibers.
Decrease in amplitude correlates best with…
Axonal loss lesions
What are the NCS findings in demyelination?
Prolonged latencies
Slowed conduction velocities
What is F-wave and what does it measure?
Supramaximal stimulation of a motor nerve while recording from a muscle.
The electrical impulse travels antidromically (conduction along the axon opposite to the normal direction of impulses) along the motor axons toward the motor neuron, backfiring and then traveling orthodromically (conduction along the motor axon in the normal direction) down the nerve to be recorded at the muscle
What is the equivalent of H-reflex?
Ankle Reflex (S1 reflex arc) It is obtained by stimulating the tibial nerve at the popliteal fossa while recording at the soleus. The electrical impulse travels orthodromically through a sensory afferent, enters the spinal cord, and synapses with the anterior horn cell, traveling down the motor nerve to be recorded at the muscle.
How is insertional activity recorded? What does it imply?
Insertional activity is recorded as the needle is inserted into a relaxed muscle.
increased in denervated muscles and myotonic disorders
decreased when the muscle is replaced by fat or connective tissue and during episodes of periodic paralysis.
How is spontaneous activity recorded? What does it imply?
Spontaneous activity is assessed with the muscle at rest, and examples include fibrillation potentials, fasciculation potentials, and myokymia and myotonic potentials. All spontaneous activity is abnormal.
How are motor unit potentials recorded? What does it imply?
MUPs are obtained while the needle is inserted into the muscle during voluntary contraction.
Characterized by recruitment pattern and MUP morphologic features (Duration, amplitude adn configuration)
What is the definition of recruitment?
measure of MUPs firing during increased force of voluntary muscle contraction
Reduced recruitment- Axonal loss
Early or rapid recruitment- myopathic processes with loss of muscle fiber
What are the electromyographic findings in neuropathic disorders with denervation and reinnervation?
MUPs disclose increased duration and amplitude, and may be polyphasic.
What are the electromyographic findings in myopathic disorders?
MUPs are of reduced duration and amplitude, and may also be polyphasic
When do you observe fibrillation potentials?
fibrillation potentials seen 3 weeks after the onset of motor axon loss
What are the repetitive stimulation findings in Myasthenia Gravis?
slow repetitive RNS (2-3Hz)
-decrement of CMAP amplitudes with a decrement of greater than 10%
What is the pathophysiology behind decremental response in Myasthenia Gravis?
decremental responses occur due to:
- normal reduction in the release of acetylcholine after subsequent stimulation
- reduced availability of receptors from the disease, leading to a loss of end- plate potentials and reduction of the motor action potentials
What are the repetitive stimulation findings in Lambert Eaton Myasthenic Syndrome?
decremental response with slow repetitive stimulation, given that there is a decline in acetylcholine release with each stimulus, leading to loss of end-plate potentials and reduction of the motor action potential.
Rapid stimulation with frequencies of 20 to 50 Hz produces an incremental response by overcoming the efflux of calcium
The incremental response has to be more than 50% to be considered diagnostic.
What is jitter in Single Fiber-EMG?
Recording with a single-fiber needle electrode positioned to detect potentials from two muscle fibers of the same motor unit.
The variability of the interpotential interval between these two potentials is the jitter, and it is abnormal in MG due to delayed neuromuscular transmission.
Single Fiber EMG, Sensitive or Specific to MG?
Sensitive
Slow-Oxidative. Type 1 or 2?
Type 1
Slow ATPase activity. Type 1 or 2?
Type 1
large oxidative capacity with large numbers of mitochondria. Type 1 or Type 2?
Type 1
Fast Oxidative glycolytic fibers and fast ATPase. Type 1 or 2?
Type 2a
Red in color and large in diameter. Type I or Type @?
Type 2
At what number of days does Wallerian Degeneration is completed?
7-10days from injury
____weeks after injury, NCS cannot localize focal axonal loss
3 weeks after injury
What are the manifestations of diabetic autonomic neuropathy?
Multiple organ systems
Cardiovascular:
- resting tachycardia, bradycardia, loss of respiratory variability of heart rate, loss of normal tachycardic response, orthostativ hypotension and increased risk of silent MI
Gastrointenstinal
-delayed gastric emptying time, constipation from colonic atony, bacterial overgrowth and diarrhea
Neurogenic bladder and Sexual Dysfunction
-impotence, erectile dysfunction, retrograde ejaculation
Abnormalities in Sudomotor Function
Hypohidrosis an hyperhidrosis
What is the definition of Amyotrophic Lateral Sclerosis according to El Escorial Diagnostic Criteria?
clinical and/or electrophysiologic evidence of both upper and lower motor neuron involvement in at least three of the four following regions: bulbar, cervical, thoracic, and lumbosacral.
What is the gene defect in Kennedy’s Disease?
expansion of a CAG repeats in the androgen receptor protein gene on the X chromosome.
What is the preganglionic neurotransmitter of Parasympathetic ANS?
A. Acetylcholine
B. Norepinephrine
C. Serotonin
D. GABA
A. Acetylcholine
What is the preganglionic neurotransmitter of Sympathetic ANS?
A. Acetylcholine
B. Norepinephrine
C. Serotonin
D. GABA
A. Acetylcholine
What is the postganglionic neurotransmitter of Sympathetic ANS?
A. Acetylcholine
B. Norepinephrine
C. Serotonin
D. GABA
B. Norepinephrine
EXCEPT SWEAT GLANDS —> Acetylcholine
What is the preganglionic neurotransmitter of Parasympathetic ANS?
A. Acetylcholine
B. Norepinephrine
C. Serotonin
D. GABA
A. Acetylcholine
What is the preganglionic receptor of Sympathetic and Parasympathetic ANS?
A. Alpha-Adrenergic Receptor
B. Nicotinic Receptor
C. Muscarinic Receptor
D. Beta-Adrenergic Receptor
B. Nicotinic Receptor
What is the postganglionic receptor of Parasympathetic ANS?
A. Alpha-Adrenergic Receptor
B. Nicotinic Receptor
C. Muscarinic Receptor
D. Beta-Adrenergic Receptor
C. Muscarinic Receptor
What is the postganglionic receptor of Somatic System?
A. Alpha-Adrenergic Receptor
B. Nicotinic Receptor
C. Muscarinjc Receptor
D. Beta-Adrenergic Receptor
B. Nicotinic Receptor
Which is not true of sympathetic nervous system?
A. Origin of Preganglionic never is at the nuclei of Spinal Cord Segments T1-T12; L1-L3 (Thoracolumbar)
B. It has a long pre-ganglionic nerve axon
C. It has a long post-ganglionic nerve axon
D. Main neurotransmitter in the receptor organs are norephinephrine
B. It has a long pre-ganglionic nerve axon
IT HAS A SHORT PRE-GANGLIONIC NERVE AXON
Sympathetic Thoracolumbar Short pre Long Post EN (except sweat glands, Ach)
Which is not true of parasympathetic nervous system?
A. Origin of Preganglionic nerve is nuclei of cranial nerves III, VII, IX and X; spinal cord segments S2-S4
B. It has a short pre-ganglionic nerve axon
C. It has a short post-ganglionic nerve axon
D. Main neurotransmitter in the receptor organs are norephinephrine
B. It has a short pre-ganglionic nerve axon
PARASYMPATHETIC- Long Preganglionic
Para CranioSpinal Long Pre Short Post Ach
Generator for positive sharp waves.
A. Muscle Fiber B. Terminal Axon C. Multiple Muscle Fibers D. Neuromuscular junction E. Motor Neuron/Axon
A. Muscle Fiber
Generator for End-Plate Noise.
A. Muscle Fiber B. Terminal Axon C. Multiple Muscle Fibers D. Neuromuscular junction E. Motor Neuron/Axon
D. Neuromuscular junction
Generator for Fibrillation.
A. Muscle Fiber B. Terminal Axon C. Multiple Muscle Fibers D. Neuromuscular junction E. Motor Neuron/Axon
A. Muscle Fiber
Generator for Complex Repetitive Discharges.
A. Muscle Fiber B. Terminal Axon C. Multiple Muscle Fibers D. Neuromuscular junction E. Motor Neuron/Axon
C. Multiple Muscle Fibers
Generator for Myokymia
A. Muscle Fiber B. Terminal Axon C. Multiple Muscle Fibers D. Neuromuscular junction E. Motor Neuron/Axon
E. Motor Neuron/Axon
Generator for Tetany
A. Muscle Fiber B. Terminal Axon C. Multiple Muscle Fibers D. Neuromuscular junction E. Motor Neuron/Axon
E. Motor Neuron/Axon
