F25 IONM pt 1 > SSEPs > Flashcards

SSEPs Flashcards

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1
Q

Cathode (-)

A

▪Black
▪Often negatively charged
▪Attracts cations/positive charge
▪Current/electrons depart from the cathode
▪Electron donor
- depolarizes

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2
Q

Anode (+)

A

▪Red
▪Often positively charged
▪Attracts electrons (anions)/negative charge
▪Electron acceptor
-hyperpolarizes

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3
Q

Cathode should ____the direction you want the stimulus to travel

A

face

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4
Q

Anodal Block

A

The cell is hyperpolarized under the anode, meaning that it is very, very difficult to activate. (Now, the stimulation intensities that we use are generally high enough to where this block doesn’t occur. )

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5
Q

the anode should always be_____ to the cathode

A

distal

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6
Q

the cathode should always be_____ to the anode

A

proximal

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7
Q

ACNS guidelines for cathode/anode placement

A

2-3 cm apart

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8
Q

If I wanted to check the integrity of the C5-T1 nerves, I would want to stimulate

A

Median Nerve (C5-T1) at the wrist
*Radial Nerve (C5-T1) at the wrist over the radius

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9
Q

If I wanted to check the integrity of the C8-T1 nerves, I would want to stimulate

A

Ulnar Nerve (C8-T1) at the wrist or the medial aspect of the elbow

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10
Q

If I wanted to check the integrity of the L4-S3 nerves, I would want to stimulate

A

Posterior Tibial Nerve (L4-S3) at the medial malleolus (ankle)

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11
Q

If I wanted to check the integrity of the (L4-S2) nerves, I would want to stimulate

A

Common Peroneal Nerve at the fibular head

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12
Q

If I wanted to check the integrity of the (L4-L2) nerves, I would want to stimulate

A

Saphenous Nerve (L2-4) at the medial mid-thigh or medial tibia

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13
Q

If I wanted to check the integrity of the (S2-S4) nerves, I would want to stimulate

A

Pudendal Nerve (S2-4) at the perineum

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14
Q

Median Nerve Stimulation - Cathode

A

–Between the tendons of the palmaris longus (PL) and flexor carpi radialis (FCR) muscles
–2 cm proximal to the wrist crease

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15
Q

Median Nerve Stimulation - Anode

A

–2-3 cm distal to the cathode
–OR on the dorsum of the wrist

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16
Q

Median Nerve Stimulation - Ground

A

–Forearm or shoulder

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17
Q

Median Nerve Stimulation should produce…

A

a clearly visible muscle twitch causing abduction of the thumb

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18
Q
A

median nerve stimulation sites

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19
Q

Radial nerve stimulation - Cathode

A

*Over the radial nerve as it passes over the extensor pollicis longus tendon

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20
Q

Radial nerve stimulation - Anode

A

2-3 cm distal to the cathode

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21
Q

Radial nerve stimulation - Ground

A

*Forearm or shoulder
*Stimulation should produce a clearly visible muscle twitch causing finger and wrist extension

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22
Q

Radial Nerve Stimulation should produce…

A

Stimulation should produce a clearly visible muscle twitch causing finger and wrist extension

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23
Q
A

radial nerve stimulation sites

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24
Q

Ulnar Nerve Stimulation - Cathode

A

–Either side of the tendon of the flexor carpi ulnaris (FCU) muscle
–2 cm proximal to the wrist crease

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25
Ulnar Nerve Stimulation - Anode
–2-3 cm distal to the cathode –OR on the dorsum of the wrist
26
Ulnar Nerve Stimulation - Anode
–Forearm or shoulder
27
Ulnar Nerve Stimulation should produce
a clearly visible muscle twitch causing abduction of the fifth digit
28
Ulnar Nerve Stimulation sites
29
Posterior Tibial Nerve - Cathode
–Midway between the medial border of the Achilles tendon and the posterior border of the medial malleolus
30
Posterior Tibial Nerve - Anode
–3 cm distal to the cathode
31
Posterior Tibial Nerve - Ground
–Calf of leg
32
Posterior Tibial Nerve stimulation should produce
a clearly visible muscle twitch causing plantar flexion of the foot
33
Posterior Tibial Nerve stimulation sites
34
Common Peroneal Nerve - Cathode
Superficial to the fibular head
35
Common Peroneal Nerve - Anode
–3 cm distal to the cathode
36
Common Peroneal Nerve - Ground
–Upper leg
37
Common Peroneal Nerve stimulation should produce
a clearly visible muscle twitch causing dorsiflexion of the foot
38
Common Peroneal Nerve stimulation sites
39
Deep Peroneal Nerve - Cathode
Top of the foot
40
Deep Peroneal Nerve - Anode
3 cm distal to the cathode
41
Deep Peroneal Nerve - Anode
Calf of leg
42
Deep Peroneal Nerve - Ground
Calf of leg
43
Deep Peroneal Nerve stimulation should produce...
a clearly visible muscle twitch causing dorsiflexion of the foot
44
Deep Peroneal Nerve stimulation sites
45
Sciatic Nerve - Cathode
–3 cm or more superior to the knee crease
46
Sciatic Nerve - Cathode
–3 cm distal to the cathode
47
Sciatic Nerve - Ground
–Upper leg
48
Sciatica Nerve stimulation should produce...
a clearly visible muscle twitch causing movement of the leg
49
Sciatica Nerve stimulation sites
50
Proximal Saphenous Nerve - Cathode
10 cm superior to the medial epicondyle of the knee in the thigh in the groove between the vastus medialis and sartorius muscles
51
Distal Saphenous Nerve - Cathode
14 cm (or more) above the medial malleolus between the gastrocnemius and the tibia bone
52
Distal Saphenous Nerve - Ground
Calf of leg
53
Proximal Saphenous Nerve - Ground
upper thigh
54
Saphenous Nerve stimulation should produce...
a clearly visible muscle twitch causing movement of the leg
55
Saphenous Nerve stimulation sites
56
Stationary response
▪ Responses obtained from groups of neurons ▪ Produced at a fixed location due to a synapse or a change in the medium ▪ Change is amplitude ▪ No change in the latency
57
Propagated response
▪ Responses obtained in transit such as in axons during transfer ▪ Produced along the nerve pathway ▪ Change is latency ▪ No change in the amplitude
58
Near field (NF) response
Responses generated close to the recording electrode
59
Far field (FF) response
Responses generated at a distance from the recording electrode
60
Recording electrodes for SSEPs
going to be located at FPZ, CP3, CP4, CP, CPZ, and then CV5.
61
Orthodromic response
▪ Responses traveling along the nerve in the intended or normal direction ▪ From axon to dendrites
62
Antidromic reponse
▪ Responses traveling along the nerve in the opposite direction ▪ From axon to soma ▪ Cannot bypass synapses
63
What causes the stim twitch?
This is an orthodromic motor, not anodromic sensory, because the sensory doesn't hook up to the musculature
64
Obligate Components
Peaks (N) Troughs (P) Obligate components are parts of a waveform that require monitoring of amplitude and latency per the ACNS guidelines.
65
ACNS Alarm Criteria for SSEPs
≥50% decrement in amplitude and/or ≥10% increase in latency
66
EP ( Erb’s Point)
Upper SSEP Obligate Component * Brachial Plexus
67
N13
Upper SSEP Obligate Component Fasciculus Cuneatus of the Dorsal Column
68
N18
Upper SSEP Obligate Component Brainstem/Thalamus
69
N20
Upper SSEP Obligate Component * Primary Somatosensory Cortex
70
PF (Popliteal Fossa)
Lower SSEP Obligate Component Sciatic Nerve
71
LP (Lumbar Potential)
Lower SSEP Obligate Component * Fasciculus Gracilis of the Dorsal Column
72
P31
Lower SSEP Obligate Component Caudal Medial Lemniscus
73
N34
Lower SSEP Obligate Component Brainstem/Thalamus
74
P37*
Lower SSEP Obligate Component * Primary Somatosensory Cortex This is an approximation This can be longer d/t anesthesia (which is normal), or shorter due to short height, etc.
75
Pudendal Nerve - Cathode (male; unilateral)
on the dorsum of the penis
76
Pudendal Nerve - Anode (male; unilateral)
distal penile shaft
77
Pudendal Nerve - Cathode (female; unilateral)
proximal infrapubic clitoris
78
Pudendal Nerve - Anode (female; unilateral)
at the labia majorum
79
Pudendal Nerve - Cathode (female; bilateral)
two cathodes at the clitoris
80
Pudendal Nerve - Anode (female; bilateral)
one anode on each labia majorum
81
Pudendal Nerve - Cathode (male; bilateral)
base of the shaft of the penis below the pubic bone
82
Pudendal Nerve - Anode (male; bilateral)
anodes outside of the cathodes
83
Pudendal Nerve - Ground (all)
Hip
84
Pudendal nerve stimulation sites
85
To ensure that activation is consistent for each stim
the current needs to be constant
86
Activation intensity
Up to 100 mA are possible
87
Upper SSEP Intensity
*Start around 15-20 mA *With high stimulation levels, crossover activation can occur as the breadth of stimulation increases
88
Lower SSEP Intensity
*Start around 40 mA
89
Supramaximal Stimulation
1)Signal is obtained 2)Intensity is increased until the amplitude no longer increases 3)Then intensity increased 10% more
90
50 mA is usually adequate as a stim strength unless...
▪Underlying pathology is present ▪Current spread from stim electrode doesn’t reach neural tissue at sufficient intensity to cause excitation (ex. large or edematous extremities)
91
Variations between patients will exist dependent on the following factors:
–Type of stimulation electrodes being used (adhesive vs needle) –Proximity of electrodes to underlying neural structures –Anesthetic management (suppresses synapses, inhibitory effect) –Conduction status of neural pathways monitored
92
SSEP pulse width is typical set to
300 µs
93
Biphasic Stimulation
▪Instead of delivering a square wave, it gives a biphasic pulse in which the amplitudes of the positive and negative portions of the stimulus can be varied ▪A biphasic pulse minimizes the buildup of charge across the skin ▪It minimizes the presence of a capacitive stimulus artifact
94
Frequency/Stimulus Rate/Repetition Rate for SSEPs
2-5 Hz
95
In order to have the noise decrease in amplitude with averaging,
the stimulus rate should not be a submultiple of any noise frequency, inc 60 hz ▪DON’T use 5.0, 4.0, or 10.0 Hz (submultiples of 60Hz)
96
▪Lower Stimulation Rates for SSEPs
(1.5-3 Hz) –Sometimes improve lower extremity responses ▪When compromise of neurological function present
97
▪Higher Stimulation Rates for SSEPs
(9 Hz uppers, 5 Hz lowers)
98
Upper SSEP recording sites
EPi & EPc Cv5 - cervical vertebra 5 (some will use Cv3 or close to the inion) Cpi & CPc
99
Lower SSEP recording sites
PFd & PFp T12s & IC (illiac crest; sometimes we like to use multiple around the area to see what area gives the best response) Cv5, FPz CPz , Cpi & CPc
100
Upper SSEP Channels (cortical)
CPc - FPz CPc - CPi
101
A minimum of ______channels are required to record SSEPs
four
102
Upper SSEP Channels (brainstem)
CPi - Epc
103
Upper SSEP Channels (spinal cord)
Cv5 - EPi - EPc
104
The typical SSEP channels we utilize will be
one cortical, one brain stem, one spinal cord, and one peripheral from the brachial plexus. Now, sometimes we'll throw in some extra cortical channels again to optimize or find which ones give us the best signal.
105
Lower SSEP Channels (cortical)
CPz - FPz CPi - CPc CPi - FPz
106
Lower SSEP Channels (brainstem)
FPz - Cv5
107
Lower SSEP Channels (Spinal Cord)
T12s - IC
108
Lower SSEP Channels (sciatic nerve)
PFd - PFp
109
Cortical SSEP LFF (ACNS Guidelines)
1 - 30 Hz
110
Cortical SSEP HFF (ACNS Guidelines)
250 - 3000 Hz
111
Spinal/Peripheral SSEP LFF (ACNS Guidelines)
100 - 200 Hz
112
Spinal/Peripheral SSEP HFF (ACNS Guidelines)
1000 - 3000 Hz
113
Cortical SSEP LFF (Typical Settings)
30 Hz
114
Cortical SSEP HFF (Typical Settings)
300 Hz
115
Spinal/Peripheral SSEP LFF (Typical Settings)
100 Hz
116
Spinal/Peripheral SSEP HFF (Typical Settings)
1000 Hz
117
Upper SSEP analysis time/sweep
* 50 - 75 ms * 5 - 7.5 ms /division
118
Lower SSEP analysis time/sweep
* 100 - 120 ms * 10 - 12 ms /division
119
SSEPs in Severely Myelopathic/Demyelinating paths
* Numbers may need to be increased * Longer conduction times mean delayed responses
120
Averages needed for SSEPs
▪ 200 - 300 recommended ▪ Increase to reduce noise, but will take longer to produce a response
121
Generator for N20, P25, P30
Sensory Cortex
122
Montage for N20, P25, P30
CPc-FPz CPc-CPi
123
Response type for N20, P25, P30
Near Field, Stationary
124
Blood supply for N20, P25, P30
Middle Cerebral Artery
125
Generator for N18
Brainstem, thalamus
126
Montage for N18
CPi-EPc
127
Response type for N18
Far Field, Stationary
128
Blood supply for P14, N18
Vertebro-basilar artery
129
Generator for P14
Caudal medial lemniscus
130
Montage for N13, P14
Cv5-Fpz
131
Response type for P14
Far Field, Propagated
132
Generator for N13
Postsynaptic activity cervical cord (Nucleus Cuneatus)
133
Response type for N13
Far Field, Stationary
134
Blood supply for N13
Posterior spinal arteries
135
Generator for N9, P10
Brachial Plexus
136
Montage for N9, P10
EPi - EPc
137
Response type for N9, P10
Near field, propagated
138
Blood supply for N9, P10
Subclavian artery
139
Generator for P37, N45
Sensory Cortex
140
Montage for P37, N45
CPz-FPz CPi-CPc CPi-Fpz
141
Response type for P37, N45
Far field, stationary
142
Blood supply for P37, N45
Anterior Cerebral Artery
143
Generator for N34
Thalamus/ Brainstem
144
Montage for P31, N34
FPz-Cv5
145
Response type for P31, N34
Far field, stationary
146
Blood supply for P31, N34
Vertebro-basilar artery
147
Generator for P31
Nucleus Gracilis, Caudal medial lemniscus
148
Generator for N22 (LP)
Fasciculus Gracilis of the Dorsal Column
149
Montage for N22 (LP)
T12s-iliac
150
Response type for N22 (LP)
Near field, propagated & stationary
151
Blood supply for N22 (LP)
Posterior spinal arteries, artery of adamkewicz
152
Generator for N9, P10
Popliteal Fossa
153
Montage for N9, P10
PFd^- - PFp^+
154
Blood supply for N9, P10
Femoral artery
154
Response type for N9, P10
Near field, propagated
155
Purpose of an SSEP
used to monitor the DCML ascending pathway – Fine Touch – Stereognosis - identifying objects by touch – Proprioception – Two - Point Discrimination – Vibration Sensation ▪ Pain and temperature are not measured with SSEP monitoring Recording of a volume conducted bioelectric event originating in an ascending pathway of the nervous system.
F25 IONM pt 1
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