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
1) What 3 EMG potentials originate from one MU firing?
2) Which EMG potentials originate from a group of MUs firing? Of these, which come from adjacent muscle fibers and which originate from the MUPs?
1) spontaneous activity, fibrillations, (+) sharp waves, and myotonic
2)
Adjacent muscle fibers: complex repetitive discharge and insertional activity
MUPs: fasciculations, myokymic, neurotonic
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)
1) Neuropraxia NCV will show __ latency, and __ CV.
2) The EMG will show what?
1) increased latency and decreased CV
2) normal, sensory dominant pathology
Remember latency and CV go hand in hand and have an inverse relationship
Axonotmesis can cause incomplete disruption and complete disruption, which will present differently on the NCV. Incomplete Disruption NCV will show __ amplitude of SNAP and CMAP, __ distal segment latency, and __ CV. Complete Disruption NCV will show __ of SNAP and CMAP in distal segment.
EMG will show ___ insertional activity, ___ and ___ at rest, and we will see the typical temporal changes of MUAP seen with neurogenic injuries. All these findings will also present with Neuronotmesis to a lesser extent except EMG will additionally show ___ at rest.
1) decr. amplitude
2) incr. distal latency
3) decr. CV
4) absence
5) prolonged
6&7) fibrillations and + sharp waves
8) fasciculations
T/F: Prognosis of axonotmesis and neurotmesis are about the same, as both cause collateral sprouting and regeneration to occur.
False
axonotmesis has a better prognosis, neurotmesis has very little chance of full recovery
With Carpal Tunnel Syndrome, EMG findings in the acute phase will be normal and in the chronic phase they will be abnormal. What are these abnormal findings? What muscles would be assessed?
1) polyphasic waves and/or incr. amplitude and duration of MUAP
2) MUAP in thenar muscles and radial lumbricals
Which is better to diagnose mononeuropathy, NCV or EMG?
NCV
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
Which is better to diagnose polyneuropathy, NCV or EMG?
NCV
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
Since we will see decr. amplitude on NCV studies with diabetic neuropathy no matter what segment of the N (ankle, knee, hip) is being tested, what is a limitation with using NCV studies to diagnose this condition? What can help us in addition to the NCV study to eliminate this limitation when diagnosing this condition?
1) A definitive location of where damage starts/ends cannot be distinguished.
2) Clinical examination!!!! NEEDS to always be done in addition to electrodx testing
Why might we not changes in SNAPs or CMAPS in the acute phases of diabetic neuropathy?
Small Ns affected first. Test ONLY evaluates LARGE Ns.
EMG results in late-stage diabetic neuropathy will include what abnormalities (LE>UE) in addition to the typical temporal changes of MUAP seen with neurogenic injuries?
Fibrillations and + sharp waves
__-__-__ disease is progressive muscle weakness that becomes noticeable in adolescence or early adulthood, but the onset of disease can occur at any age. Disease is caused by a gene mutation the produce proteins involved in structure and function of __ __. Symptoms usually being in feet and lower legs & progress to fingers, hands, and arms because __ N are affected first (__ muscles).
1) Charcot-Marie-Tooth Disease
2) myelin sheath
3) larger/longer
4) smaller
T/F: Charcot-Marie-Tooth Disease only affects motor Ns.
False
It affects sensory and motor Ns. Sensory effects come later.
Which is better to diagnose Charcot-Marie-Tooth Disease (a chronic myelin disorder), NCV or EMG?
NCV, still a NEUROGENIC condition.
EMGs are better for myopathies (of course it also gives info abt neurogenic injuries which is why we use them later in chronic phases)
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 conditions (3) in the chronic stages will show fibrillations and + sharp waves in addition to the typical temporal changes of MUAP seen with neurogenic injuries?
Charcot-Marie-Tooth Disease
Diabetic Neuropathy
Carpal Tunnel Syndrome (if neurotmesis, these will be seen plus fasciculations)
What condition is the most common cause of rapidly evolving motor paresis/paralysis and sensory deficits? What body system other than attacking the PNS does this condition affect?
1) Guillain-Barre Syndrome (GBS)
2) immune system
GBS causes Ns & N root inflammation, leading to ___ patches of demyelination. It progresses over __ to __ and recovery has a __ to __ progression.
1) FOCAL
2&3) days to weeks KAHOOT Q
4&5) proximal to distal progression of recovery
Which is better to diagnose GBS (an acute myelin disorder), NCV or EMG?
NCV, looking for the focal Conduction blocks
T/F: GBS NCV findings will be abnormal at the conduction block and at adjacent segments of the N (body parts)
1) FALSE, findings are FOCAL, only at the CB location.
GBS NCV findings __ amplitude and __ distal latency d/t rapid myelin sheath loss. Depending on how proximal the CBs are (disease progression), a ____ can also show significant abnormal results.
1) decr.
2) incr./prolonged
3) F wave
EMG is typically NOT helpful in ruling in demyelinating disorders like GBS in the ___ phase. EMG findings in the chronic stages GBS can be ___ or you may see decreased recruitment and/or compensatory rapid firing of MUAPs in affected muscles.
1) acute
2) normal
Muscular dystrophy is a ___ disorder that involves a group of diseases that cause progressive weakness and loss of ___ __. It’s caused by the absence of ___, a protein that helps maintain __ integrity.
1) myopathic
2) muscle mass
3) dystrophin
4) muscle
Which is better to diagnose Muscular dystrophy (a myopathic disorder), NCV or EMG?
EMG finallyyyyy!
a MYOPATHIC disorder
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
Of the conditions we discussed…
1) Which 2 will have focal findings for NCV?
2) The only 1 where EMG MIGHT be normal?
3) The only 1 where clinical exam findings will be focal & unilateral/asymmetrical?
4) The only 1 where EMG will show abnormalities in acute and chronic stages?
1) Carpal tunnel & GBS
2) GBS, acute myelin disorder
3) Carpal tunnel, mononeuropathy
4) Muscular dystrophy, myopathy
