IIA11 - Interpretation of EDX testing Flashcards
(197 cards)
1
Q
What nerves and spinal cord segments supply the trapezius muscle?
A
Suprascapular nerve
C6-C7
2
Q
What nerves and spinal cord segments supply the supraspinatus muscle?
A
Suprascapular nerve
C6-C7
3
Q
What nerves and spinal cord segments supply the infraspinatus muscle?
A
Suprascapular nerve
C6-C7
4
Q
What nerves and spinal cord segments supply the Deltoideus muscle?
A
Axillary nerve
C7-C8
5
Q
What nerves and spinal cord segments supply the triceps brachii muscle?
A
Radial nerve
C7-C8-T1
6
Q
What nerves and spinal cord segments supply the brachialis muscle?
A
Musculocutaneous nerve
C6-C7-C8
7
Q
What nerves and spinal cord segments supply the biceps brachii muscle?
A
Musculocutaneous nerve
C6-C7-C8
8
Q
What nerves and spinal cord segments supply the extensor digitorum communis muscle?
A
Radial nerve
C7-C8-T1
9
Q
What nerves and spinal cord segments supply the extensor digitorum lateralis muscle?
A
Radial nerve
C7-C8-T1
10
Q
What nerves and spinal cord segments supply the extensor carpi radialis muscle?
A
Radial nerve
C7-C8-T1
11
Q
What nerves and spinal cord segments supply the ulnaris lateralis muscle?
A
Radial nerve
C7-C8-T1
12
Q
What nerves and spinal cord segments supply the flexor carpi ulnaris muscle?
A
Ulnar nerve
C8-T1
13
Q
What nerves and spinal cord segments supply the interossei palmere muscle?
A
Ulnar nerve
C8-T1
14
Q
What nerves and spinal cord segments supply the gluteus medius muscle?
A
Cranial gluteal nerve
L6-L7-S1
15
Q
What nerves and spinal cord segments supply the gluteus superficialis muscle?
A
Caudal gluteal nerve
L7
16
Q
What nerves and spinal cord segments supply the satorius muscle?
A
Femoral nerve
L4-L5-L6
17
Q
What nerves and spinal cord segments supply the quadratus femoris muscle?
A
Femoral nerve
L4-L5-L6
18
Q
What nerves and spinal cord segments supply the tensor fasciea latae muscle?
A
Cranial gluteal nerve
L6-L7-S1
19
Q
What nerves and spinal cord segments supply the biceps femoris muscle?
A
Sciatic nerve
L6-L7-S1
20
Q
What nerves and spinal cord segments supply the semitendinosus and semimembranosus muscles?
A
Sciatic nerve
L6-L7-S1
21
Q
What nerves and spinal cord segments supply the gastrocnemius muscle?
A
Sciatic nerve
L6-L7-S1
22
Q
What nerves and spinal cord segments supply the flexor digitorum lateralis muscle?
A
Tibial nerve
L7-S1
23
Q
What nerves and spinal cord segments supply the tibialis cranialis muscle?
A
Peroneal nerve
L6-L7
24
Q
What nerves and spinal cord segments supply the interossei planteres muscle?
A
Tibial nerve
L7-S1
25
What nerves supply the genioglossus (tongue) muscle?
Hypoglossal nerve
26
What nerves supply the temporalis muscle?
Mandibular branch of cranial nerve 5
27
What nerves supply the masseter muscle?
Mandibular branch of cranial nerve 5
28
What nerves supply the obicularis oculi muscle?
Facial nerve
29
What nerves supply the digastricus muscle?
Cranial belly = mandibular branch of CN 5
Caudal belly = facial nerve
30
What nerves supply the sternocephalicus muscle?
Ventral branches of the cervical and accessory nerves
31
What nerves supply the cleidocephalicus muscle?
Accessory nerve
32
What nerves supply the trapezius muscle?
Accessory nerve
33
What nerves supply the latissimus dorsi muscle?
Caudal pectoral nerve & thoracodorsal nerve
34
What nerves supply the obliquus externus abdominus muscle?
Iliohypogastric nerve & Ilioinguinalis nerve
35
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Normal
Insertional activity
36
The following is a description of what EMG finding?
Brief burst of positive or negative, high frequency, high amplitude spikes lasting a few hundred milliseconds then disappearing. Makes a sharp crisp static sound.
Insertional activity
Due to movement of the needle within the muscle
37
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Normal
Motor unit action potentials (MUAP) in an awake horse
38
The following is a description of what EMG finding?
Biphasic or triphasic wave with an initial positive (downward) deflection followed by a major negative deflection with an amplitude ranging between 100-3000 uV and 1-12msec duration/
Motor unit action potential (MUAP)
Due to voluntary movement of the animal
39
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Miniature endplate potentials and endplate spikes
Can be confirmed by redirecting the needle towards a different direction (away from the neuromuscular junction)
40
The following is a description of what EMG finding?
Small mono or biphasic waves with an initial negative (upwards) direction with irregular depolarization and occasional higher amplitude and longer duration spikes with similar morphology and random pattern. Sounds like waves on a seashore with occasional sounds from a frying pan.
Miniature endplate potentials and endplate spikes
Due to measuring action potentials directly from the neuromuscular junction that are constantly occurring spontaneously
41
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed within the **yellow circles** and the image on the right (closeup)?
Abnormal
Fibrillation potentials
42
The following is a description of what EMG finding?
Brief spikes of low amplitude (1.5msec, 20-500uV) typically triphasic waves with an initial positive (downward) deflection. A relatively consistent firing pattern and sound like rain on a tin roof or wrinkling paper.
Fibrillation potentials
Produced by a single muscle fiber due to hypersensitivity of the post-synaptic acetylcholine receptors following denervation
43
How is severity of fibrillation potentials on an EMG graded?
On a scale from 1+ to 4+
44
The following description would be associated with what grade for fibrillation potentials on an EMG?
One to few potentials in more than one area of the muscle
1+
45
The following description would be associated with what grade for fibrillation potentials on an EMG?
Moderate numbers of potentials in three or more areas of the muscle
2+
46
The following description would be associated with what grade for fibrillation potentials on an EMG?
Large numbers of potentials in 3 or more areas of the muscle?
3+
47
The following description would be associated with what grade for fibrillation potentials on an EMG?
Potentials completely filling the screen
4+
48
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Abnormal
Positive sharp waves
Produced by a single muscle fiber due to hypersensitivity of the post-synaptic acetylcholine receptors following denervation
49
The following is a description of what EMG finding?
A biphasic potential composed of an initial positive (downward) deflection followed by a smaller slower negative deflection before returning to baseline. Sound like a car racing by.
Positive sharp waves
Produced by a single muscle fiber due to hypersensitivity of the post-synaptic acetylcholine receptors following denervation
50
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Abnormal
Myotonic discharges
Repetitive firing of an individual muscle fiber with waxing and waning frequency
51
What conditions cause myotonic discharges on EMG?
Myotonic muscular dystrophies
Myotonia congenita
Paramyotonia congenita
52
The following is a description of what EMG finding?
Positive or negative potentials which fire at regular but exponentially increasing or decreasing frequency. Triggered by needle movement. Sound like a chain saw or dive bomber. So **not** start or stop abruptly.
Myotonic discharges
Caused by instability or dysfunction in the muscle fiber membrane or of the membrane ion channels
53
Is the electrical activity seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Abnormal
Complex repetitive discharges
Spontaneous activity from multiple muscle fibers which depolarize in a time locked fashion
54
The following is a description of what EMG finding?
Time-locked depolarizations that have a regular firing rate and amplitude with an abrupt stop and start and do **not* wax in wane in frequency. Identical morphology from one depolarization to the next. Sound like a machine-gun firing.
Complex repetitive discharges
Usually found in chronic myopathies or neuropathies (e.g. Cushing's myopathy). Unlikely to be seen in acute disease where unhealthy fibers reside next to healthy fibers.
55
Fasciculations typically arise from which of the following generator sites?
Motor neuron/ axon
Individual muscle fiber
Multiple muscle fibers
Motor neuron/ axon
56
Myokymia typically arise from which of the following generator sites?
Motor neuron/ axon
Individual muscle fiber
Multiple muscle fibers
Motor neuron/ axon
57
Neuromyotonia typically arise from which of the following generator sites?
Motor neuron/ axon
Individual muscle fiber
Multiple muscle fibers
Motor neuron/ axon
58
Fibrillations and positive sharp waves typically arise from which of the following generator sites?
Motor neuron/ axon
Individual muscle fiber
Multiple muscle fibers
Individual muscle fibers
59
Myotonia typically arise from which of the following generator sites?
Motor neuron/ axon
Individual muscle fiber
Multiple muscle fibers
Individual muscle fibers
60
Complex repetitive discharges typically arise from which of the following generator sites?
Motor neuron/ axon
Individual muscle fiber
Multiple muscle fibers
Multiple muscle fibers
61
Peripheral nerve hyperexcitability can clinically manifest as what four potential motor signs?
Fasciculations
Myokymia
Neuromyotonia
Cramps or Tetany
62
Is the electrical activity (red arrows) seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Abnormal
Can be seen in both normal and abnormal muscle
Fasciculation potentials
Occurs from spontaneous firing of an entire motor unit (rather than a single fiber)
63
The following is a description of what EMG finding?
Polyphasic potential with a slow irregular firing pattern (less than 1-2 Hz). Sound like pop corn popping.
Fasciculation potentials
Arise from single, spontaneous occasional discharges from one hyperactive motor unit cell body or axon
64
Is the electrical activity (red and green arrows) seen on this EMG normal or abnormal?
What is the name of the electrical activity being displayed?
Abnormal
Myokymia
Clinically manifests as rippling movements of the overlying skin
65
The following is a description of what EMG finding?
Rhythmic spontaneous repetitive discharges in <1 sec bursts of potentials which sound like soldiers marching.
Myokymia
Caused by motor neuron or axon hyperexcitability and clinical presents as rippling muscles on the skin
66
What is neuromyotonia and how does it relate to myokymia?
Neuromyotonia is a characterized by muscle stiffness and delayed relaxation after contraction due to sustained firing of the muscle membrane
Neuromyotonia and myokymia represent a spectrum of severity of the same pathology with neuromyotonia being more severe
67
The following is a description of what EMG finding?
Repetitive and overlapping MUAPs at high rates (up to 150 Hz) with abrupt onset and rapid cessation and short duration (second to minutes). Frequency usually increases at the beginning and decreases towards the end.
Cramps
68
The following is a description of what EMG finding?
Prolonged and sustained doublets, triplets, or multiplets of MUAPs in both agonist and antagonist limb muscles.
Tetany/ Tetanus
Typically reserved for when signs are specifically caused by tetanospasmin
69
Which of the points on the image correspond to the stimulating sites and recording sight for performing a motor nerve conduction velocity (MNCV) test using the radial nerve?
Name the recording muscle
Stimulating 1: A
Stimulating 2: B
Recording: E
Extensor carpi radialis
70
Which of the points on the image correspond to the stimulating sites and recording site for performing a motor nerve conduction velocity (MNCV) test using the ulnar nerve?
Name the recording muscle
Stimulating 1: F
Stimulating 2: G
Recording: I
Palmar interosseous muscle
71
Which of the points on the image correspond to the stimulating and recording site for performing a motor nerve conduction velocity (MNCV) test using the median nerve?
Name the recording muscle
Stimulating 1: C
Stimulating 2: D
Recording: H
Flexor carpi radialis muscle
72
Which of the points on the image correspond to the stimulating sites and recording site for performing a motor nerve conduction velocity (MNCV) test using the sciatic-tibial nerve?
Name the recording muscle
Stimulating 1: M
Stimulating 2: N
Stimulating 3: O
Recording: P
Plantar interosseous muscle
73
Which of the points on the image correspond to the stimulating sites and recording site for performing a motor nerve conduction velocity (MNCV) test using the sciatic-peroneal nerve?
Name the recording muscle
Stimulating 1: L
Stimulating 2: J
Recording: K
Tibialis cranialis muscle
74
In a normal dog undergoing a motor nerve conduction velocity (MNCV) test, the latency to the compound muscle action potential (CMAP) is variable based on what factor?
The distance between the stimulating and recording sites
75
When looking at a motor nerve conduction velocity (MNCV) test, what is latency?
The time from the stimulating artifact to the start of the CMAP
76
When looking at a motor nerve conduction velocity (MNCV) test, what is amplitude?
Either the distance from baseline to the largest negative (upwards) peak OR from peak-to-peak
77
What is considered a normal amplitude for a compound muscle action potential (CMAP) when performing a motor nerve conduction velocity (MNCV) test?
15 - 20 mV
78
When looking at a motor nerve conduction velocity (MNCV) test, what is area?
The area under the curve for the first peak or for both the first and second peaks - a value that is calculated by the EDX machine (we don't do calculus here)
79
When evaluating a motor nerve conduction velocity (MNCV) test, what is temporal dispersion?
When CMAP duration is prolonged due to a loss of synchrony of action potentials
80
How do you calculate motor nerve conduction velocity?
81
What is the normal MNCV of the Sciatic-tibial nerve?
60 - 70 m/s
82
What is the normal MNCV of the ulnar nerve?
60 - 70 m/s
83
What is the normal MNCV of the Sciatic-peroneal nerve?
70 - 80 m/s
84
What is the normal MNCV of the Radial nerve?
70 - 80 m/s
85
What is the normal MNCV of the Median nerve?
70 - 80 m/s
86
When performing a motor nerve conduction velocity (MNCV) test, what is residual latency?
The amount of delay (time) that is lost at the neuromuscular junction
87
At what age are adult numbers for a motor nerve conduction velocity (MNCV) test reached?
6 months to 1 year of age
88
How is MNCV affected by temperature?
Velocity decreases linearly for each degree of temperature below 37 degrees by 1.7 m/sec per degree
89
How does the size of the dog affect the MNCV speed?
Longer nerves conduct slightly slower than shorter nerves
Longer nerves will also have a slightly decreased amplitude and slightly greater temporal dispersion
90
What pattern of findings will be seen on a MNCV test when there has been axonal loss?
Decreased amplitude and area of the CMAP (smaller CMAPs)
If severe enough to affect all axons, may see slowing of the MNCV, if the fastest axons are spared then MNCV will be normal
91
What pattern of findings will be seen on a MNCV test when there has been demyelination?
Marked decrease in MNCV (typically <70%)
Minor decrease in CMAP amplitude (no more than 80%) - if demyelination is uniform then no change in CMAP is seen (same # of signals arrive, just later)
92
What pattern of findings will be seen on a MNCV test when there is a myopathy?
Typically MNCV testing is normal
93
What pattern of findings will be seen on a MNCV test when there is a junctionopathy?
Normal MNCV and CMAP with post-synaptic junctionopathies
Normal MNCV with decreased CMAP amplitude in pre-synaptic junctionopathies (less muscle depolarizes)
94
What measure of F-wave is most useful for screening of abnormalities?
The minimal latency
95
What conditions are F-wave's best for diagnosing?
Proximal motor nerve disorders, particularly idiopathic polyradiculoneuritis
96
How many stimulations should be recorded for the purpose of evaluating F-wave latency?
10 - 15 stimulations should be used to get a good representation of F-wave latency
97
At what rate should stimulations be performed when evaluating F-wave latency and what does this frequency avoid that may occur at a faster frequency?
< 0.5 Hz
Avoid superimposition of the signals and avoid triggering of the inhibitory Renshaw cells
98
What is central latency a calculation of, when performing MNCV and associated testing?
A measure of the conduction time along the proximal portion of the motor nerve
99
How is central latency calculated?
100
What is the F-wave conduction velocity?
The conduction velocity (essentially the same thing as MNCV) but of the proximal portion of the nerve
101
How is the F-wave conduction velocity calculated?
F-wave conduction velocity (m/s) = the distance from the stimulating electrode to the spinal cord (mm), divided by the central latency (msec)
102
What are the normal results of F-wave conduction velocity?
They tend to be towards the higher end of the normal range of the MNCV of the same nerve
103
When considering F-wave evaluation, what is persistence?
% of trials with an observed F-wave
Total number of recordings with an F-waves observed divided by the total number of records
104
What is the F-ratio?
It compared the conduction time of the proximal segment (F-wave conduction velocity) to the conduction time of the distal segment (MNCV)
105
How is the F-ratio calculated?
F- ratio = [(F-latency) - (M-latency) - 1] / [2x (M-Latency)]
106
What pattern of findings will be seen on an F-wave evaluation in a dog with idiopathic polyradiculoneuritis?
Increased F-wave latency and decreased amplitude
107
What pattern of findings will be seen on EMG, MNCV, and F-wave study in a dog with brachial plexus trauma?
EMG and MNCV will be normal if testing is performed before distal denervation has occurred
The F-wave will be absent or have markedly reduced persistence
108
What pattern of findings will be seen on F-wave evaluation in a dog with degenerative lumbosacral stenosis?
The F-wave latency and F-wave ratio are likely to both be increased compared to normal dogs
109
What pattern of findings may be seen on F-wave evaluation in a dog with a myelopathy (e.g. Dachshund with a disk herniation)?
The mean F-wave duration has been found to positively correlate with degree of pelvic limb dysfunction
110
When performing a repetitive nerve stimulation (RNS), how do you calculate % decriment?
111
What % decriment at 1-3 Hz on repetitive nerve stimulation (RNS) is consistent with disorders affecting synaptic transmission (e.g. myasthenia gravis)?
10% decrement
112
What type of disorder may display "fascilitation" (increasing amplitude) on repetitive nerve stimulation at high stimulation rates such as 50 Hz?
Why does this occur?
Pre-synaptic disorders (e.g. Botulism)
During rapid stimulation, Ca accumulates in the pre-synaptic terminal resulting in an increased probability of vesicle release into the synaptic cleft = the body is able to escape the effect of the botulinum toxin
113
Which of the points on the image correspond to the recording site used when performing a sensory nerve conduction velocity (SNCV) test using the lateral superficial radial nerve?
Where is the stimulating electrode placed?
Recording site: B
Stimulating site: dorsal aspect of the paw
114
Which of the points on the image correspond to the recording site used when performing a sensory nerve conduction velocity (SNCV) test using the ulnar nerve?
Where is the stimulating electrode placed?
Recording site: F
Stimulating site: Lateral aspect of digit 5 just proximal to the accessory carpal bone
115
Which of the points on the image correspond to the recording site used when performing a sensory nerve conduction velocity (SNCV) test using the peroneal nerve?
Where is the stimulating electrode placed?
Recording site: J
Stimulating site: dorsal aspect of the paw
116
Which of the points on the image correspond to the recording site used when performing a sensory nerve conduction velocity (SNCV) test using the tibial nerve?
Where is the stimulating electrode placed?
Recording site: N
Stimulating site: plantar aspect of the paw
117
When performing a SNCV test, how is latency measured?
Latency is measured from the onset of the stimulating artifact to the initial positive (downward) deflection
118
When performing a SNCV test, how is amplitude measured?
Measured peak-to-peak from the first positive (downward) peak to the first negative (upwards) peak
119
How is SNCV calculated?
The distance between the recording site and stimulating site (mm) divided by the latency (msec) = SNCV (m/s)
120
What is the normal SNCV for the radial nerve (dog)?
60 - 70 m/s
121
What is the normal SNCV for the ulnar nerve (dogs)?
55 - 75 m/s
122
What is the normal SNCV for the Tibial and Peroneal nerve (dogs)?
64 m/s
123
What is the normal SNCV for the saphenous nerve (dogs)?
~ 65 m/s
124
What is the normal SNCV for the radial nerve (cats)?
80 - 90 m/s
125
What is the normal SNCV for the ulnar nerve (cats)?
90 - 100 m/s
126
What is the normal SNCV for the peroneal nerve (cats)?
80 - 90 m/s
127
What is the normal SNCV for the tibial nerve (cats)?
75 - 85 m/s
128
By what age does SNCV reach adult values?
By 6 months of age
129
What affect does temperature have on SNCV?
SNCV decreases linearly for each drop in degree below 37 degrees. Decreases by 1.7 m/s for each degree.
130
How does location along the neuron affect the results of the SNAP and SNCV?
SNAP and SNCV will be normal if the damage is proximal to the dorsal root ganglion (the region of the nerve being measures is still healthy and connected to the cell body
Is damage occurs distal to the dorsal root gangling, then wallerian degeneration will occur of the distal segment and impact the SNCV results
131
What is typically seen on a SNCV test with demyelinating disease?
There is a decrease in the SNCV
132
What is typically seen on a SNCV test with axonal loss
Reduction in amplitide of the SNAP (though amplitude is hard to evaluate on SNCV)
133
What happens to the H-wave with an M-wave and F-wave are visible?
The H-wave will be blocked
Requires a sub-maximal stimulus to be evaluated
134
When performing a somatosensory evoked potential using the tibial nerve, where would your recording electrodes be placed to measure a cord dorsum potential?
L4-L5 vertebra
Next to the interarcuate ligament
135
When performing a somatosensory evoked potential using the tibial nerve, where would your recording electrodes be placed to measure the sciatic root component?
L7-S1 vertebra
Next to the interarcuate ligament
136
When performing a somatosensory evoked potential using the radial nerve, where would your recording electrodes be placed to measure the cord dorsum potential?
C7-T1 vertebra
Next to the interarcuate ligament
137
What are the **three* types of stimulus that can be used during BAER testing?
1) Condensation
2) Rarefaction
3) Alternating
138
How does the condensation type of stimulus work during BAER testing?
The membrane moves inward first then outward
139
How does the rarefaction type of stimulus work during BAER testing?
The membrane moves outward first then inward
140
How does the alternating type of stimulus work during BAER testing?
The membrane alternates between the two other types
141
Which stimulus types can display cochlear microphonics during a BAER and what wave do the cochlear microphonics obscure?
Condensation and Rarefaction stimulus types can contain cochlear microphonics which obscure wave 1 of the BAER
142
What are the pros and cons of using an alternating type stimulus for BAER testing?
Cochlear microphonics are canceled out which allows a clear view of wave 1
The waveforms of the BAER are less definitive since alternating averages the waveforms of both other stimulus types which inherently have slightly different latencies
143
How are positive and negative potential on a BAER displayed differently than other electrodiagnostic tests?
Position potentials are displayed as upward deflections on a BAER whereas positive potentials are typically displayed as downward deflections in other electrodiagnostic tests
144
How is latency for any given wave on a BAER calculated?
The distance from the stimulating artifact to the positive peak of the wave in question
145
How is amplitude for any given wave measured on a BAER?
The amplitude is measures from the positive peak of that wave the negative peak immediately following that wave
146
What is the source of wave I on a BAER?
Ipsilateral cochlear nerve
147
What is the source of wave II on a BAER?
Ipsilateral cochlear nucleus / proximal cochlear nerve
148
What is the source of wave III on a BAER?
Dorsal nucleus of the trapezoid body
+/- Ipsilateral or contralateral superior olivary complex of the pons
149
What is the source of wave IV on a BAER?
The origin of this wave is uncertain
150
What is the source of wave V on a BAER?
Ipsilateral and/or contralateral caudal colliculus
151
What is the source of wave VI and VII on a BAER
The origin of these waves is uncertain
152
What are inter-wave latency most useful for evaluating when interpreting a BAER?
For helping to localize a lesion along the auditory pathway
153
What would be the appearance of a BAER in a dog with congenital sensorineural deafness?
Absence of all waveforms at all intensities when using both air and bone conductors
154
What else may result in BAER findings similar to sensorineural deafness?
Congenital or acquired disorders that cause complete cochlear degeneration
155
What would be the appearance of a BAER in a dog with conductive hearing loss?
An increase in BAER threshold needed to elicit the waveforms
Reduction in amplitudes with an absolute increase in peak latencies (normal inter-wave latencies)
Normal waveform and thresholds when using bone conduction
156
What would be the typical appearance of a BAER test in a dog with acquired sensorineural deafness?
Typically there is an increased auditory threshold required with both air and bone conductors
This occurs sue to dysfunction of the cochlea and/or the cochlear nerve
157
What would be the typical appearance of a BAER test in a dog with a brainstem lesion?
Absence of one or more waveforms
A decrease in wave V / wave I amplitude ratio
An increase in interpeak latencies
158
What would be the typical appearance of a BAER test if a patient with a forebrain lesion?
Should not result in visible abnormalities on a BAER test
159
What are the two questions that should always be asked when evaluating a pattern on an EEG?
1) Is it artifactual, or is it arising from the cerebral cortex
2) If arising from the cortex, is it physiologic or is it pathologic?
160
What are physiologic artifacts?
List 4 examples of the most common physiologic artifacts
Artifacts that are produced by organs of the body other than the brain
1) Muscles artifact
2) Heart (EKG)
3) Tongue movement
4) Eye movement
161
What is the appearance of muscle artifact on an EEG?
Low amplitude, high frequency waveforms
162
What is the appearance of blinking or eye movement artifact on an EEG?
Very large amplitude, low frequency waveforms that will be most pronounced in the frontal electrodes
163
What does an EKG artifact look like on EEG?
Waveforms which match in timing with the heart rate. An EKG can be coupled with the EEG recording to better track the EKG artifact
164
What does an electrode pop artifact look like on an EEG?
A massive amplitude, brief signal affecting only one electrode caused by electrode disconnect
165
What causes 50/60 Hz interference and how is it corrected?
Alternating current
Can occur if one electrode had greater impedance than the others
Can be addressed by performing the EEG within a Faraday cage or using a 50/60 Hz notch filter
166
As a general rule, the following described waveforms represent what finding on an EEG?
A pattern seen in a single channel with abnormal waveforms, with frequency <1 Hz or >70 Hz, and appear precisely periodic
Patterns that fit this description are most likely artifacts on the EEG
167
What is the following concept when evaluating a pattern of clinical significance on an EEG?
Field
The signal is often recorded by multiple electrodes at once
168
What is the following concept when evaluating a pattern of clinical significance on an EEG?
Lag
The electrode closest to the source of the signal will record the signal first with an increased latency the further away the electrode is
169
What is the following concept when evaluating a pattern of clinical significance on an EEG?
Gradient
The electrode closest to the source will record the highest amplitude
170
How do you localize the source of a signal on a referential montage when performing an EEG?
Look for the channel with the largest amplitude and shortest latency
171
How do you localize the source of a signal on a bipolar montage when performing an EEG?
Identify the location of the phase reversal
Where the phase changes from upwards to downwards in two subsequent channels that share a common electrode
The common electrode is the course of the signal
172
The delta band range is made up of what frequencies on an EEG?
When are delta frequencies typically seen?
< 4 Hz
During sleep
173
The theta band range is made up of what frequencies on an EEG?
When are theta frequencies typically seen?
4 - 8 Hz
With drowsiness
174
The alpha band range is made up of what frequencies on an EEG?
When are alpha frequencies typically seen?
8 - 13 Hz
Wakefulness that is restful or reflective, eyes closed
175
The beta band range is made up of what frequencies on an EEG?
When are beta frequencies typically seen?
14 - 30 Hz
In an alert, active mind
176
The gamma band range is made up of what frequencies on an EEG?
When are gamma frequencies typically seen?
30 - 80 Hz
Problem solving, highly concentrated mind
177
What is the Mu band range on EEG and how does it differ from alpha activity?
Mu activity is of a similar frequency to alpha waves (7-11 Hz) but is not attenuated/blocked by opening of the eyes
178
What benefit does monitoring an EEG during natural sleep provide for EEG studies aimed at identifying the presence of epileptiform discharges?
Natural sleep can increase the sensitivity for interictal epileptiform discharges
179
What are 3 common sleep transients that may be seen during an EEG recording when a patient is sleeping?
1) Vertex waves - typically seen at Cz location
2) Sleep spindles - typically seen in the central region
3) K-complexes - large amplitude bi- or tri-phasic wave with initial negative deflection; tend to be in frontal regions
180
How might a sleep EEG be different in a patient with narcolepsy compared to a normal patient?
In what two other scenarios might this difference be seen?
A narcoleptic patient may exhibit Stage R (REM sleep) at the onset of a sleep cycle
1) Sleep deprivation
2) Certain drug withdrawal
181
What may be seen on an EEG of a patient with REM sleep disorder that would be suggestive of this condition?
Abnormal amounts of muscle activity (muscle artifact) during the Stage R (REM sleep) phase when usually no muscle tone is picked up
182
What is background slowing on an EEG and what is its cause?
Slower frequency waves (e.g. theta or delta waves) than is expected for the mental status of the patient (e.g. alert)
Usually occurs due to focal white or grey matter lesions
183
What degree of asymmetry of the amplitude of waves on an EEG is considered abnormal?
Amplitude asymmetry of more than 50% is alpha rhythm or of more than 35% is beta rhythm
184
How do you interpret an abnormal degree of amplitude asymmetry when reviewing an EEG?
The area of lower amplitude is likely the source of the lesion unless a skull defect is present
The amplitude of waveforms beneath the skull defect will be increased due to reduced resistance of the signal
185
What is a burst-suppression pattern on an EEG?
A burst suppression pattern is a pattern where 50-99% of the EEG recording is supressed/ attenuated
186
When is a burst-supression pattern most commonly seen on EEG and how might it be used for determining prognosis?
This pattern is most commonly seen in comatose patients
Greater lengths of suppression are associated with a poorer prognosis
187
What are the **three** most common interictal epileptiform discharges on EEG?
1) Spikes
2) Sharp waves
3) Spike and Slow Wave
188
What are the features of an electrographic seizure on EEG?
Any epileptiform pattern lasting longer than 10 seconds with frequency of > 2.5 Hz or with evolution of its morphology
189
What is the definition of electrographic status epilepticus on EEG?
An electrographic seizure lasting longer than 10 minutes, or electrographic seizures taking up more than 20% of a 60 minute recording
190
What is the definition of an electroclinical seizure on EEG?
When a clinical manifestation of a seizure matches an epileptiform pattern on the EEG
191
What is the definition of an electroclinical status epilepticus on EEG?
When an electroclinical seizure lasts longer than 5 minutes (convulsive) or 10 minutes (non-convulsive) or if it makes up >20% of a 60 minute recording
192
The following epileptiform discharge pattern on EEG is associated with what type of clinical seizure activity?
3-4 Hz spike and wave, frontal max
Absence seizure
193
The following epileptiform discharge pattern on EEG is associated with what type of clinical seizure activity?
4-6 Hz spike and wave, antero-dominant
Myoclonic seizures
194
>10 Hz fast waves with occasional spike and wave
Clonic seizures
195
>10 Hz wave with increasing and decreasing amplitude and frequency
Tonic seizures
196
>10 Hz wave of increasing and decreasing amplitude and frequency that is interrupted by slow waves
Tonic-Clonic seizures
197
What EEG findings would be consistent with a diagnosis of brain death?
8 electrodes measured over 30 minutes with lack of response to intense somatosensory or audiovisual stimulus with absence of EEG activity
