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Clinical Procedures III > Final Exam > Flashcards

Final Exam Flashcards

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0
Q

What is electromyography.

A

Examines the electrical activity of skeletal muscle fibers at rest and during voluntary activation of muscle
Assess VOLUNTARY potentials (no actual stimulation)

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1
Q

What is electroneurography (nerve conduction velocity testing).

A

Assess the integrity of peripheral nerves as reflected by the speed at which electrical signals travel along them
Conduction speed of a healthy nerve is ~40-70 M/sec
Assess evoked potential (actual stimulation)

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2
Q

What are the different electrodes used?

A

Active (muscle belly, usually black)
Reference (away from excitable ts, usually tendon junction and usually red)
Ground (bony prominence, usually green)

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3
Q

What are surface electrodes?

A

Usually small plates made of silver or other conductive metals
Placed outside the ms on surface of skin
Most require use of conductive gel or paste

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4
Q

What are the disadvantages of surface electrodes?

A

Rapid, low amplitude potentials are attenuated
Fine details of individual motor units can’t be routinely obtained because of varying degrees of skin and subcutaneous ts thickness
Only used for superficial ms

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5
Q

What are the uses of surface electrodes?

A

Better for assessing the total electrical activity of the ms

For most NCV studies

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6
Q

What are needle electrodes?

A

Used for detailed study of motor unit activity because they are inserted between ms fibers
Bring the recording surface if electrode in closer proximity to the individual motor units
Pick-up signals from small, restricted territories

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7
Q

What are the types of needle electrodes?

A

Monopolar (single needle, need reference and ground)
Concentric/coaxial (shaft/cannula-reference, inside-active, need ground)
Bipolar/double coaxial (shaft/cannula-ground, inside-active and reference)
Fine wire- more with mvt, very small

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8
Q

What is a pre-amplifier?

A

A differential amplifier which amplifies the voltage difference between the recording electrodes and the common ground electrode. Unwanted interference signals of equal (common) voltage at all electrodes (60 Hz) are not amplified. Produces the initial gain in signal

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9
Q

What is common mode rejection ratio?

A

The ratio of differential signal to common signal (which can’t be fully eliminated) amplification that is high:low

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10
Q

What is a main amplifier?

A

A device for amplifying or increasing the electrical current or voltage
Primary function is gain amplification

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11
Q

What is the amplifier gain?

A

Sensitivity
Indicates the factor by which the EMG voltage produced at the electrode is multiplied by another amplifier
Measured in microvolts
>sensitivity, <gain

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12
Q

What is a filter?

A

Reduces unwanted interference outside the frequency bandwidth of electrical signals of interest

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13
Q

What are low pass (high cut) filters?

A

Eliminates all high frequency energy from an electrical signal

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14
Q

What are high pass (low cut) filters?

A

Eliminates all low frequency energy from the signal

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16
Q

What is a notch filter?

A

Selectively eliminate selective frequencies from an electrical signal

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17
Q

What are the potentials displayed on?

A

Computer screen or oscilloscope

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18
Q

What is sweep speed?

A

Time

0.2-500 msec per divsion

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19
Q

What is the sensitivity range?

A

2-10,000 microvolts

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20
Q

What is the loud speaker used for?

A

Primarily for during EMG exam to allow the examiner to listen to the electrical activity
Helpful to experienced examiner in detecting abnormal potentials

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21
Q

What is the stimulator used for in ENMG?

A

Employs an isolated circuit having no connection to common system ground thereby reducing possible artifact introduction
Generates a rectangular, monophasic pulsed current that depolarizes the nerve under the cathod

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22
Q

What are the stimulator controls for ENMG?

A

Amplitude: supramax response (motor studies)
Duration: convention 100 microseconds
Rate: most 1-2 pps

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23
Q

What are the sources of electrical error or artifact?

A

Dirty electrodes, broken lead wires, electrode wire movement, poor ground electrode location, incorrect connection of electrode at input box, electrode paste (gel), bridging between ground and stimulating electrode, audio feedback from EMG (especially at high gains), power cords in wall receptacles nearby, fluorescent lights, electronic dimmers, other electrical interference (diathermy, radio, TV)

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24
Q

What are the solutions to sources of electrical error or artifact?

A

Dedicated circuit

Pre-amp away from main amplifier

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25
What are the four conditions that measurements for electromyography are made under?
Needle insertion Rest Minimal voluntary contraction Maximal voluntary contraction
26
What is needle insertion?
muscle fibers are mechanically stimulated, cut, and injured | Lead to a brief burst of electrical activity followed by silence
27
What is rest?
No electrical activity because the tone of muscle at rest resides in the viscoelastic properties of its CT components and myofibers
28
What is minimal voluntary contraction?
MUAP | Sufficient contraction to detect a single motor unit action potential
29
What is maximal voluntary contraction?
Activation of all motor units within the muscle and all are contraction close to their maximal rates of discharge; interference pattern and recruitment order (should be full and from small to large)
30
What are the common waveforms in electromyography?
Varies with the location of the recording electrode Triphasic waveforms are most commonly seen when using monopolar or concentric needle electrodes, but MUs with two (biphasic) and four phases may also be seen
31
What are the parameters to electromyography?
Amplitude: 200 to 5,000 microvolts Duration: 5 to 15 msec Frequency: increases with increasing muscle force Configuration: biphasic or triphasic
32
How does amplitude influence action potentials?
Dependent on several variables, particularly the distance between the recording electrode and the contracting muscle fibers; and the number of muscle fibers per unit (sums up muscle fiber to one MU)
33
How does duration influence action potentials?
Dependent on spatial distribution of fibers of the same unit in relation to recording electrode More compact less duration Less compact more duration
34
How do phases influence action potentials?
Dependent on temporal coincidence (synchronicity) of action potentials of those muscle fibers nearest the recording electrode (unhealthy will have >4 phases)
35
What are other factors that influence action potentials?
Age (increase age decrease amplitude) Temperature (decrease temp decrease amp) Fatigue (increase fatigue decrease interference) Disuse atrophy (decrease amp, polyphasic)
36
What is the normal EMG at needle insertion?
Brief burst of electrical activity that ceases as soon as needle movement stops Due to mechanical irritation of muscle fibers
37
What is the normal EMG at rest?
Electrical silence Implies complete neuromuscular inactivity Exceptions to absence of electrical activity at rest include: end-plate activity and fasciculation potentials
38
What are normal end-plate activities?
Miniature end-plate potentials (MEPPs) End-plate spikes Both disappear when needle is moved away from the neuromuscular juntion
39
What are miniature end-plate potentials?
Miniature end-plate potentials at neuromuscular junction secondary diffusion of ACh across synaptic cleft Amplitude 10-40 microvolts (smaller); duration 1-2msec (shorter); hissing/sea shell sound; painful
40
What are end-plate spikes?
Spontaneous discharge of single muscle fibers Amplitude 100-300 microvolts (slightly smaller); duration 2-4msec (shorter); frequency 5-50 sec; biphasic with initial negative deflection; high-pitched crackling sound; p!
41
What are fasciculation potentials?
Normal or in pathology; unclear origin Spontaneous discharge of one or more MU Commonly seen in AHC disorders Normal amp and duration, irregular frequency and waveform
42
What is a minimal voluntary contraction (MUAP)?
Study of the parameters of a single MU action potential Amplitude 200-5,000 microvolts Duration 5-15 msec Frequency 5-15 pps Bi or tri- phasic occasional mono or poly Clear distinct thump or pop
43
What is maximal voluntary contraction?
With increasing voluntary effort, the amount of electrical activity increases; small MUs are recruited first, followed by progressively larger MUs as the force of contraction increases; individual MU cannot be distinguished as the interference pattern develops; a full interference pattern is characterized by a muffled or rumbling sound
44
What are the abnormal EMGs at needle insertion?
Prolonged and increased insertional activity | Decrease or absence of normal insertional activity
45
What is prolonged and increased insertional activity?
After needle movement has stopped Indicates hyper excitability of the ms membrane Commonly seen following acute denervation and inflammatory ms disease
46
What is decreased or absent insertional activity?
Implies absence of muscle ts in proximity to the needle | Can be secondary to pathological loss of ms ts with fibrotic replacement (i.e. chronic neuropathy)
47
What are the abnormal EMGs at rest?
Fibrillations Positive sharp waves Fasciculation
48
What are fibrillation potentials?
Spontaneous repetitive contraction of single ms fibers Reflection of ms fiber membrane instability which may result from denervation, metabolic dysfunction, inflammatory and degenerative disease of ms fiber Amplitude: 20-300 microvolts Duration: 1-5 msec Wave biphasic with initial positive deflection Frequency: 1-30 pps High pitched click
49
What are positive sharp waves?
Reflection of ms fiber membrane instability Originates from single ms fiber Present only in the first few secs after needle mvt Important sign of abnormality at rest Indication of reversal of polarity Not as common as fibrillation potentials Amplitude: 10-10,000 microvolts Duration: up to 10 msec Frequency: 5-10 pps Biphasic with initial positive deflection followed by a gradual return in the negative direction Thud or plop
50
What are fasciculation potentials?
Pathological occur in lesions of AHC disorders Significance determined by coexistence with fibrillations and positive sharp waves Similar to normal MUAP but usually polyphasic Thump (ALS, post-polio)
51
What are the abnormal EMGs of minimal voluntary contraction?
Polyphasic potential Nascent potential Giant motor unit potential Absent
52
What are polyphasic potentials?
Multiple phases Result from non-synchronous firing of ms fibers in the MU Represent the electrical expression of either a deteriorating or regenerating MU Seen in incomplete ms denervation and in MD
53
What are nascent potentials?
Low voltage Long duration Polyphasic potentials Seen during nerve regeneration (early sign of reinnervation)
54
What are giant motor unit potentials?
Large MUAPs with amplitudes up to 10 microvolts seen in chronic diseases of the LMN (primarily in diseases of AHC) Represents reorganization of the MU ALS or post-polio
55
What are absent potentials?
Occurs in complete nerve injuries | May occur with advanced myopathy
56
What are the abnormal EMGs for maximal voluntary contractions?
Neuropathic patterns Myopathic patterns Absent
57
What are neuropathic patterns?
Incomplete or partial interference pattern due to the loss of MUs Fewer MUs firing at higher frequencies "pickett fence" with axonotmeisis and neurotmeisis
58
What are myopathic patterns?
Normal number of MUs but there is a reduction in the number of ms fibers within individual MUs Full interference pattern but low amplitude at maximal effort due to the decreased power of the MU secondary to the loss of ms fibers
59
What is absent maximal voluntary contraction?
Occurs in complete nerve injuries | May also occur with advanced myopathy
60
What are the normal findings in and EMG?
Insertional activity: brief Resting activity: silent MUAP: biphasic or triphasic units Interference pattern: Full small to large
61
What are the EMG findings in UMN lesion?
Insertional activity: normal, rief Resting activity: silent MUAP: normal MUAP or absent Interference pattern: incomplete or absent
62
What are the EMG findings in myopathy/MD?
Insertional activity: normal, brief Resting activity: silent (could see denervated potentials) MUAP: decreased amplitude Interference pattern: full, low amplitude
63
What are the EMG findings in myotonia/inability to relax?
Insertional activity: increased, waxing/waning discharge Resting activity: silent MUAP: decreased amplitude, increased number, waxing/waning Interference pattern: full, low amplitude
64
What are the EMG findings in polymyositis?
Insertional activity: increased Resting activity: fibrillations, positive sharp waves MUAP: decreased amplitude, increased number Interference pattern: full, low amplitude
65
What are the clinical applications of nerve conduction studies?
Used to diagnose diffuse polyneuropathy (abnormalities in multiple nerves) Used to pinpoint focal lesions, such as nerve entrapments Used t evaluate the severity of a nerve injury
66
What is a stimulus artifact or prepulse?
Indicates onset of stimulus pulse
67
What is an evoked action potential?
Action potential elicited by a stimulus
68
What is a compound muscle action potential (CMAP)?
Represents the sum of action potentials of individual MUs | Produced by electrical stimulation of the motor nerve supplying the ms
69
What is a compound sensory nerve action potential (CSNAP)?
Represents the sum of action potentials of individual nerve fibers Produced by electrical stimulation of a sensory or mixed nerve
70
What is latency?
Measurement of time (msec) from initiation of stimulation (stimulus artifact) to onset of evoked potential (motor) or peak of negative phase (sensory)
71
What is orthodromic conduction?
Same direction as physiological conduction
72
What is antidromic conduction?
Opposite direction to normal physiological conduction
73
What is the neuromuscular junction delay?
Latency in motor NCV studies also includes the time in the barbarized axon and the time for neuromuscular transmission Neuromuscular junction delay time can be eliminated by stimulating two sites along the nerve and using the distance between the stim sites and the difference in the latencies to calculate the conduction velocity
74
What is the duration for NCV studies?
50-100 microsec for sensory | 100-200 microsec for motor
75
What is the frequency for NCV studies?
1 pps or control frequency with stimulator
76
What is the intensity for NCV studies?
Supramax intensity with motor | Sensory-level intensity with sensory
77
What does the amplitude for NCV studies show?
Reflects the number of muscle/nerve fibers activated
78
What does the duration parameters for NCV studies show?
Reflects the synchrony of fibers activated
79
What is the configuration of NCV studies show?
Normal shape of CMAP is biphasic | Normal shape of CSNAP is bi/triphasic
80
What is nerve conduction velocity?
Conduction speed by which electrical signals travel along nerves (distance/difference)
81
What is the H reflex?
Electrically induced equivalent of the tendon tap | Most commonly used to asses the achilles tendon reflex pathway (S1 reflex arc)
82
How does the tendon tap reflex work?
Tap tendon; stretch ms spindle; impulses travel up afferent arc along IA fibers through dorsal horn; synapse occurs on homonymous AHC; impulse travels along efferent arc
83
How does the electrical reflex work?
Bypasses spinde stretch; directly depolarizes IA fibers
84
What is the procedure for assessing S1 reflex arc?
Recording electrodes over soleus; stimulating electrodes over tibial n in popliteal fossa; use sub-max stimulus; latency approx 30 msec
85
What is the F wave?
Late CMAP resulting from backfiring of antidromically activated motor neurons (tests any peripheral nerve)
86
What is the latency of a F wave include?
Time to ascend antidromically to AHCs Delay time in the AHCs Time required for AP to descend othrodromically to ms fibers
87
Why do F waves vary?
F waves var yin latency, configuration, and amplitude with repeated stimuli because different groups of motor neurons are activated with each stimulus
88
What is the procedure in testing F waves?
Recording electrode same as NCV; stimulation over distal stimulation sites; use supra-max intensity; record 10-20 f waves and average them; use shortest latency appx 30 msec in UE and 50 msec in LE
89
What is the purpose of a repetitive nerve stimulation (RNS) test?
Assesses function of neuromuscular junction
90
What are the parameters of a RNS?
Current: pulsatile/pulsed Duration: 100 microsec Intensity: supra-max Frequency: 2-3 pps
91
What does a normal muscle show with a RNS?
< 5% drop in amplitude of potential over time due to depleting ACh pool (time period varies due to intensity)
92
What does a muscle with NMJ disorder show with RNS?
> 10% drop in amplitude over same time period Classic myasthenia gravis > main test for this Eaton Lamberth for pediatrics
93
What is EMG biofeedback used for?
Monitoring, detection, or assessment of skeletal ms activity Increasing (facilitation) or decreasing (inhibition of ms activity Devices provide audio and/or visual feedback
94
What is EMG biofeedback facilitation used for?
Increase ms activity after sx or injury Normalize balance of muscles Improve motor control after CNS dysfunction Increase control of pelvic floor ms
95
What is EMG biofeedback inhibition used for?
Decrease activity in ms with spasticity Decrease activity associated with postural stress Decrease activity associated with chronic p!
96
Where is the recording electrode placed in EMG biofeedback?
Placed over the ms | Usually disposable and pre gelled with fixed inter electrode distance
97
Where is the ground electrode placed in EMG biofeedback?
Placed close but usually not over ms
98
What are the differences of close and wide electrode placement in EMG biofeedback?
Close electrode placement detects activity from restricted area of ms Wide electrode placement detects activity from larger volume of ms and may pick up activity from nearby ms (cross-talk)
99
What are some common tie bits about electrode placement in EMG biofeedback?
``` Try to standardize placement Palpate if pt can actively contract Verify placement with MMT if possible Measure from bony landmarks Mark electrode sites ```
100
What are the sensitivity settings used with EMG biofeedback?
Gain: 1-1000 microvolts Lowest gain (1 microvolts) has greatest sensitivity Highest gain (1,000 microvolts) has lowest sensitivity Set sensitivity based on tx goal
101
What is the threshold settings used with EMG biofeedback?
Facility: if goal is increase in activity, set threshold so that pt must increase effort in order to get feedback Inhibitory: if goal is decrease in activity, set threshold so that pt must decrease effort to stop feedback

Clinical Procedures III (2 decks)

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