CNP Course - EMG Waveforms Flashcards by Lauren Chorny

origin of EMG potentials

single muscle fibers

How well did you know this?

Not at all

Perfectly

EMG potentials that fire alone

end plate spikes
fibrillation potentials
myotonic discharges

How well did you know this?

Not at all

Perfectly

EMG potentials that fire in groups

adjacent muscle fibers -
- complex repetitive discharge
- insertion activity

How well did you know this?

Not at all

Perfectly

EMG potentials - spontaneous

fasciculation potentials
myokymic discharges
neurotonic discharges

How well did you know this?

Not at all

Perfectly

regular firing pattern with linear change is:

fibrillation potential

How well did you know this?

Not at all

Perfectly

regular firing pattern with no change is:

complex repetitive discharge

How well did you know this?

Not at all

Perfectly

regular firing pattern with exponential change is:

myotonic

How well did you know this?

Not at all

Perfectly

irregular firing pattern is:

random change
end plate spike

How well did you know this?

Not at all

Perfectly

semi rhythmic firing pattern is

motor unit potential

How well did you know this?

Not at all

Perfectly

increased insertional activity

early denervation
normal variants (snap, crackle, pop)

How well did you know this?

Not at all

Perfectly

decreased insertional activity

fatty or fibrotic tissue
severe atrophy
periodic paralysis
ischemic muscles
technical

How well did you know this?

Not at all

Perfectly

grading fibrillation potentials

reflects number of denervated fibers:
1+ persistent single trains
2+ moderate numbers
3+ many in all areas
4+ completely fill baseline

How well did you know this?

Not at all

Perfectly

associated disorders of fibrillation potentials - neurogenic

anterior horn cell disorders -e.g. ALS
radiculopathies - “active”
mononeuropathies - “severe”
axonal peripheral neuropathies

How well did you know this?

Not at all

Perfectly

associated disorders of fibrillation potentials - myopathic

inflammatory (e.g. polymyositis, IBM)
toxic myopathies (e.g. statin, hydroxychloroquine)
muscular dystrophies
metabolic (e.g. acid maltase)
fiber necrosis, fiber splitting, vacuolar damage

How well did you know this?

Not at all

Perfectly

associated disorders of fibrillation potentials - severe NMJ disorders

myasthenia gravis (severe)
LEMS
botulism

How well did you know this?

Not at all

Perfectly

single motor unit

all the muscle fibers innervated by one AHC

How well did you know this?

Not at all

Perfectly

factors affecting MUP morphology

technical: electrode type, filter settings
physiologic: muscle, subject’s age, temperature

How well did you know this?

Not at all

Perfectly

rise time

time from peak positive deflection to peak negative deflection
represents proximity to muscle fiber action potential
should be <0.5msec

How well did you know this?

Not at all

Perfectly

amplitude

sum of action potentials of muscle fibers closest to recording electrode
usually less than 15 muscle fibers (1-8)
determined by diameter of muscle fibers, number of muscle fibers, and temporal distribution of potentials closest to electrode

How well did you know this?

Not at all

Perfectly

duration

time from leaving baseline until return
- synchrony of firing, fiber density, area of motor unit, intervening tissue, proximity to recording electrode, age and muscle
most limb muscles: 8-12msec

How well did you know this?

Not at all

Perfectly

temporal course of MUP changes in acute neurogenic injury:

normal
1 minute: reduced recruitment
1-2 months: unstable, turns
2-6 months: polyphasic, long duration
>6 months: long duration

How well did you know this?

Not at all

Perfectly

myotonic discharges

regular, exponential change, wax/wane
stock plane

How well did you know this?

Not at all

Perfectly

associated disorders myotonic discharges - prominent

myotonic dystrophy (DM1 and DM2)
myotonia congenita
paramyotonia congenita
hyperkalemic periodic paralysis

associated disorders myotonic discharges - occasional/infrequent

polymyositis
acid maltase deficiency (esp paraspinals)
drug-induced myotonia
- cholesterol lower agents, colchicine

associated disorders myotonic discharges - rare

neurogenic disorders (e.g. axonal neuropathies, radiculopathies)

complex repetitive discharges

regular, fixed intervals (abrupt onset, cessation, change) rate 3-40Hz configuration: few-multiple spikes, stable or unstable jackhammer

associated disorders complex repetitive discharges - neurogenic

anterior horn cells - e.g. ALS, SMA radiculopathies - chronic, old axonal peripheral neuropathies - longstanding

associated disorders complex repetitive discharges - myopathic

inflammatory - e.g. IBM muscular dystrophies

associated disorders complex repetitive discharges - normal

iliopsoas biceps

fasciculation potentials

firing pattern: single, random, irregular, 1-100 per minute form: no standard configuration, often distant irregular pattern popcorn

associated disorders fasciculation potentials - neurogenic

anterior horn cell disorders - e.g. ALS, SMA radiculopathies axonal peripheral neuropathies

associated disorders fasciculation potentials - other

hyperexciteable nerve syndromes (cramp-fasciculation syndrome) tetany hyperthyroidism anti-cholinesterase medication (e.g. mestinon)

fasciculation potentials normal in

benign fasciculations

myokymic discharges

1 or few MUP firing repetitively in bursts burst pattern: regular or semirhythmic marching

associated disorders myokymic discharges - extremities

radiation chronic nerve compression (CTS) AIDP, CIDP gold therapy rattlesnake venom

associated disorders myokymic discharges - most likely

radiation nerve injury

associated disorders myokymic discharges - facial

multiple sclerosis sarcoid, tuberculoma brainstem glioma polyradiculopathy meningeal carcinomatosis facial palsy syringobulba ALS

neuromyotonic discharges

regular (wane), very high frequency racecar

associated disorders neuromyotonic discharges

syndrome of continuous muscle fiber activity (Isaac's) tetany anticholinesterase poisoning chronic spinal muscular atrophies

recruitment ratio

maximum firing rate/# of nearby MUP most limb muscles have ratio of

reduced recruitment

increase in firing rate without increase in MUPs

disorders with reduced recruitment

hallmark of neurogenic process correlates with weakness

disorders with reduced recruitment - neurogenic

axon loss (e.g. mononeuropathies, radiculopathies, neuropathies) loss of anterior horn cells (e.g. ALS) conduction block (e.g. Saturday night palsy)

disorders with reduced recruitment - myopathies

severe myopathy with loss of all muscle fibers in some motor units (e.g. end-stage muscular dystrophy)

recruitment grading

fastest rate of firing of 1st MUP when 2nd MUP recruited and/or recruitment ratio 1+ (mild) rate of 1st >10Hz, ratio >5 2+ (moderate) rate of 1st >15Hz, ratio >7.5 3+ (severe) rate of 1st >20Hz, ratio >10

poor activation

effort pain central disorder: stroke, myelopathy

disorders of unstable (varying) motor unit potentials - neurogenic

ongoing reinnervation after axonal loss - e.g. ALS, recovering radiculopathy

disorders of unstable (varying) motor unit potentials - NMJ disorders

myasthenia gravis LEMS

disorders of unstable (varying) motor unit potentials - myopathies

reinnervating muscle fibers

phases and turns

asynchronous firing phase = baseline crossings +1 polyphasic MUP = 5 or more phases

when do you see polyphasic MUPs

myopathies

MUP changes in myopathies

reduced motor unit territory - reduction of # of muscle fibers/motor unit - reduction in muscle fiber size decreased duration of MUP decreased amplitude of MUP increased phases of MUP (desynchrony)

disorders with short duration MUPs - neurogenic

early reinnervation from severe nerve damage (nascent MUP)

disorders with short duration MUPs - myopathic

inflammatory - e.g. polymyositis, IBM muscular dystrophies myotonic dystrophy congenital myopathies toxic myopathies (not corticosteroids)

disorders with short duration MUPs - NMJ disorders

myasthenia gravis LEMS botulism

MUP changes in neurogenic disorders

loss of axons -> reduced number of MUP, reduced recruitment collateral sprouting -> loss of synchrony of fibers, change in appearance