Electrodiagnostic Testing Flashcards
Electrodiagnostic Testing is used to assess fxn/integrity of ___ and the ___ it innervates. The most common 2 types are __ and __. They usually are done together, can be performed by multiple disciplines including us, may involve other special tests.
1) PNS
2) musculature
3&4) electromyography (EMG) and Nerve Conduction Velocity Studies (NCV)
NCV provides info on how well ___ travel up/down peripheral nerves. EMG measures how ___ respond to APs at rest and w/ activity.
1) APs (electric signals)
2) muscles
T/F: NCV/EMG can help diagnose weakness in ICU and muscle disease.
true
T/F: NCV/EMG cannot provide info like time course of disease, nature of pathology, distribution of pathology, anatomic location of pathology, physiological status of lesion, and data for clinical/lab use.
false
They CAN provide all info
Primary components of NCV (4).
1 Motor N conduction testing
2 Sensory N conduction testing
3 F-wave study
4 H-reflex study
NCV are usually used on thicker/larger diameter and longer Ns like Ulnar, Femoral, etc
Motor N conduction testing assesses ___ (CMAP). CMAP measures the ___ of the final AP before NMJ, a direct measure of the strength of the AP. This testing also analyzes the proximal and distal ___ (time) and ___ __. __ __ is length/(Prox Latency - Distal Latency).
1) Compound Motor Action Potential
2) amplitude
3) latency
4) Conduction Velocity
we are able to assess the presence/integrity of myelin on the axon of the N
AP is sent at diff locations/segments of the N (ex: if testing ulnar N, AP is sent at levels of the elbow and armpit)
Sensory N conduction testing assesses ____ (SNAP) & has the same process as CMAP except AP is sent at one location on the N. Also, the SNAP wave will be (smaller/bigger) than the CMAP wave. Since sensory Ns are ___, the signals can be sent in 2 diff directions (___ vs ___)
1) Sensory N AP
2) smaller
3) bipolar
4) orthodromically vs antidromically
Orthodromic (a) is the __ direction of sensory APs and antidromic (b) is the __ direction of sensory APs. Which is more common usually d/t examiner preference and it’s easier to do although both directions are equally as effective?
1) natural
2) opposite
3) antidromic
___ assesses retrograde “rebound” motor impulse which travels full length of motor axon and back at max contraction. Its primarily used to evaluate ___ damage/demyelination. Pathologies like GBS and radiculopathy can be picked up here.
1 F wave
2 PROXIMAL
___ follows the muscle stretch reflex arc. This can evaluate N root lesions and ___ motor neuron lesions like SC damage.
1 H-reflex
2 UPPER
NCV studies interpret the amplitude (related to ____ in the nerve), latency (a marker of time most affected by ___), and conduction velocity (speed is affected by both ___ loss and __). Mod slowing conduction velocity is indicative of LARGER, fast-conducting fibers lost. Marker slowing is indicative of ___.
1) # of axons
2) demyelination
3) axonal loss
4) demyelination
5) demyelination
NCV can test both sensory and motor N conduction, diff segments of the N, the contralateral side, multiple Ns (UE/LE), and can interpret the time course of a suspected disorder. What are 2 limitations to NCV studies?
1 Easily affected by age, temp, obesity, and edema
2 Must be diligent about electrode placement
Electromyography (EMG) tests ___ __ of __ and can identify disorders that interfere with ___ __. EMG will evaluate muscular dystrophies, the NMJ, N disorder that cause peripheral neuropathies and disorders than affect motor neuron (___) in SC.
1 electrical activity of muscles
2 muscular contraction
3 anterior horn cells
During an EMG, a __ is inserted into the muscle belly. __ activity, ___ and __ when the muscle is at rest, and activity when the muscle is __ are all assessed.
1) needle
2) insertional
3) fasciculations
4) fibrillations
5) activated/contracted
needle will pick up a certain perimeter of fibers. Some abnormalities will show a larger perimeter of fibers being assessed on EMG, hint for later
The __ __ includes the cell body & dendrites of a motor neuron, the multiple terminal axons, and the muscle fibers that it innervates. ___ is the summed electrical activity of all muscle fibers activated within the motor unit.
1) Motor unit
2 Motor Unit AP (MUAP, MUP)
Is the EMG recording normal or abnormal?
normal
Normal insertional activity time is __ ms. Healthy muscle at rest is generally electrically __ when the needle electrode is not moving other than normal spontaneous activity of __, __, and __.
1) 50-200 ms
2) SILENCE IS GOLDEN
3) MEPPS (muscle end plate potentials), EPPs (end plate potentials), and EPS (end plate spikes)
Abnormal muscle activity at rest is related to insertional activity:
↓ in normal insertional activity = ___
↑ in normal insertional activity = ___
Prolong insertional activity = ___ (3)
1) loss of muscle fibers
2) neuropathy or myopathic disorders
3) post-acute denervation, inflammatory muscle disorders, and muscular dystrophy
3 types of electrical activity at rest indicative of neuropathy or myopathy are __, __, and __. __ and ___ are associated with a single muscle fiber degenerating anywhere b/w ___ and the peripheral N. They suggest there’s a __ motor neuron issue.
1-3) fibrillations, positive sharp waves, and fasciculations
4&5) fibrillations (a) and positive sharp waves (b)
6) anterior horn cells
7) LOWER
Fasciculations are spontaneous, repetitive, __-like contractions commonly seen w/ __ conditions or conditions involving ___ motor neurons.
1 twitch
2 chronic
3 alpha
these can be normal but become pathological when they are PROLONGED
What are 3 more other types of abnormal muscle activity at rest?
1 Complex Repetitive Discharge usually seen w/ chronic damage
2 Myokymic invol. muscle contractions
3 Myotonic muscular dystrophy/muscle wasting
Time to play…Name that abnormality!
Myokymic discharge
Name that abnormality!
Complex repetitive discharge
Name that abnormality!
fibrillation potentials
Name that abnormality!
myotonic discharge
Name that abnormality??
its a trick, this one’s NORMAL
Normal electrical activity when a muscle is contracted shows a wave with 3 peaks called ___.
There’s a slight variation in size b/w waves but that is also normal.
triphasic
Being essentially damage to the muscle belly with a neuronal origin, myopathy MUPs will show decreased amplitude and incr. frequency of APs due to __ of muscle fibers and test picking up more adjacent fibers.
Shrinking
An acute neurogenic injury will show MUPs undergoing a temporal course of changes. What will the MUP look like immediately post-injury, 1 mo. post, 2-6 mo. post, and chronically (>6 mo)?
Immediately = reduced recruitment, incr. freq. of APs (hard to discern this from norm sometimes)
1 Mo. = unstable MUP, polyphasic
2-6 Mo. = polyphasic, long duration
>6 Mo. = long duration, triphasic
T/F: As the damaged axon is regrowing, collateral sprouting will attempt to compensate for the damage.
True
** Regrowth occurs at a rate of 1in/month!
Think about polyphasic stages as the new sprouting axons trying to figure out their new “job”. Then in chronic they’ve figured it out (back to triphasic) but because they are doing “2 jobs” they have to put in more effort (larger amplitude seen in chronic phase)
Pic of normal EMG with contraction
slight contraction
max contraction
Myopathic lesion vs Neurogenic lesion EMGs. What’s a noticeable difference between how they will present on an EMG (think size/amplitude).
Neurogenic lesions will have waves bigger in size/amplitude.
Mononeuropathy Types:
___ is pressure, compression or stretch injury distorts myelin sheath without Wallerian degeneration.
___ is when demyelination causes axonal damage & Wallerian degeneration. Axonal regeneration + collateral sprouting takes place.
___ is severe injury causing complete disruption of axon, schwann cells, and endoneurium. Collateral sprouting is relied more than regeneration.
1 Neuropraxia
2 Axonotmesis
3 Neurotmesis
What is the most common compressive mononeuropathy?
Carpal tunnel syndrome
(severity will determine if damage is neuropraxia, axonotmesis, or neurotmesis)
Diabetic Neuropathy is a __neuropathy. Hallmark signs include ___ involvement of sensory, motor, and autonomic fibers. Small N fibers are effected first then progresses to ___ N fibers. The axon’s __ is impacted. Damage progresses distal to proximal and sensory fibers are effected EARLIER than motor.
1) Polyneuropathy
2) symmetrical
3) large
4) diameter
NCV (SNAP and CMAPs) results for Diabetic neuropathy: primary abnormality seen is ______ which correlates w/ the degree of axonal damage.
Decreased Amplitude
will see this no matter where electrodes are placed; remember SNAP changes will be seen sooner than CMAP changes
Charcot-Marie-Tooth Disease NCV findings include the UNIFORM slowing of ___ and ___ CV. In late/chronic stages, __ amplitude as well. EMG findings in the chronic stage will be __
1) latency (incr. time)
2) decr. CV
3) decr. amplitude
4) fibrillations and + sharp waves in addition to the typical temporal changes of MUAP seen with neurogenic injuries
small note from PPT: late stages, axonal abnormalities will show
Which is better to diagnose GBS (an acute myelin disorder), NCV or EMG?
NCV, looking for the focal Conduction blocks
Muscular dystrophy NCV findings are typically ___. EMG findings in acute or chronic stages of muscular dystrophy include early __ recruitment, ___ and ___ insertional activity, __ and __ __ waves, and a ___phasic MUAP with __ amplitude and duration.
1) normal
2) maximum
3&4) increased and prolonged
5&6) fibrillations and + sharp waves
7) polyphasic
8) decreased
