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