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Neuro Boards > CNP Course - EMG Waveforms > Flashcards

CNP Course - EMG Waveforms Flashcards

1
Q

origin of EMG potentials

A

single muscle fibers

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2
Q

EMG potentials that fire alone

A

end plate spikes
fibrillation potentials
myotonic discharges

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3
Q

EMG potentials that fire in groups

A

adjacent muscle fibers -
- complex repetitive discharge
- insertion activity

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4
Q

EMG potentials - spontaneous

A

fasciculation potentials
myokymic discharges
neurotonic discharges

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5
Q

regular firing pattern with linear change is:

A

fibrillation potential

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6
Q

regular firing pattern with no change is:

A

complex repetitive discharge

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7
Q

regular firing pattern with exponential change is:

A

myotonic

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8
Q

irregular firing pattern is:

A

random change
end plate spike

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9
Q

semi rhythmic firing pattern is

A

motor unit potential

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10
Q

increased insertional activity

A

early denervation
normal variants (snap, crackle, pop)

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11
Q

decreased insertional activity

A

fatty or fibrotic tissue
severe atrophy
periodic paralysis
ischemic muscles
technical

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12
Q

grading fibrillation potentials

A

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

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13
Q

associated disorders of fibrillation potentials - neurogenic

A

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

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14
Q

associated disorders of fibrillation potentials - myopathic

A

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

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15
Q

associated disorders of fibrillation potentials - severe NMJ disorders

A

myasthenia gravis (severe)
LEMS
botulism

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16
Q

single motor unit

A

all the muscle fibers innervated by one AHC

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17
Q

factors affecting MUP morphology

A

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

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18
Q

rise time

A

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

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19
Q

amplitude

A

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

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20
Q

duration

A

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

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21
Q

temporal course of MUP changes in acute neurogenic injury:

A

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

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22
Q

myotonic discharges

A

regular, exponential change, wax/wane
stock plane

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23
Q

associated disorders myotonic discharges - prominent

A

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

24
Q

associated disorders myotonic discharges - occasional/infrequent

A

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

25
Q

associated disorders myotonic discharges - rare

A

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

26
Q

complex repetitive discharges

A

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

27
Q

associated disorders complex repetitive discharges - neurogenic

A

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

28
Q

associated disorders complex repetitive discharges - myopathic

A

inflammatory - e.g. IBM
muscular dystrophies

29
Q

associated disorders complex repetitive discharges - normal

A

iliopsoas
biceps

30
Q

fasciculation potentials

A

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

31
Q

associated disorders fasciculation potentials - neurogenic

A

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

32
Q

associated disorders fasciculation potentials - other

A

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

33
Q

fasciculation potentials normal in

A

benign fasciculations

34
Q

myokymic discharges

A

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

35
Q

associated disorders myokymic discharges - extremities

A

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

36
Q

associated disorders myokymic discharges - most likely

A

radiation nerve injury

37
Q

associated disorders myokymic discharges - facial

A

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

38
Q

neuromyotonic discharges

A

regular (wane), very high frequency
racecar

39
Q

associated disorders neuromyotonic discharges

A

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

40
Q

recruitment ratio

A

maximum firing rate/# of nearby MUP
most limb muscles have ratio of </= 5 (15Hz: 3 MUP, 20Hz: 4 MUP)

41
Q

reduced recruitment

A

increase in firing rate without increase in MUPs

42
Q

disorders with reduced recruitment

A

hallmark of neurogenic process
correlates with weakness

43
Q

disorders with reduced recruitment - neurogenic

A

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

44
Q

disorders with reduced recruitment - myopathies

A

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

45
Q

recruitment grading

A

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

46
Q

poor activation

A

effort
pain
central disorder: stroke, myelopathy

47
Q

disorders of unstable (varying) motor unit potentials - neurogenic

A

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

48
Q

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

A

myasthenia gravis
LEMS

49
Q

disorders of unstable (varying) motor unit potentials - myopathies

A

reinnervating muscle fibers

50
Q

phases and turns

A

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

51
Q

when do you see polyphasic MUPs

A

myopathies

52
Q

MUP changes in myopathies

A

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)

53
Q

disorders with short duration MUPs - neurogenic

A

early reinnervation from severe nerve damage (nascent MUP)

54
Q

disorders with short duration MUPs - myopathic

A

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

55
Q

disorders with short duration MUPs - NMJ disorders

A

myasthenia gravis
LEMS
botulism

56
Q

MUP changes in neurogenic disorders

A

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

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