2. Neurography: Low ampl CMAP
Normal sensibility, strong muscles: If the CMAP of APB has an amplitude < 4mV and CMAP from ADM is normal,
and the SNAP from dig III is normal which is a likely reason
1. CTS
2. LEM
3. Technical problem
4. Polyneuropathy
3. Neurography: Low ampl CMAP
Normal sensibility, strong muscles: If the CMAP of APB has an amplitude < 4mV and CMAP from ADM is normal,
and the SNAP from dig III is normal which is a likely reason
1. CTS
2. LEM
3. Technical problem
4. Polyneuropathy
LEM is very rare and technical problems common. Answer on these grounds
4. Neurogaphy: Low ampl CMAP
If the CMAP of ADM and APB have an amplitude < 2mV , sensory signal OK
which is a likely reason
1. CTS
2. LEM
3. Technical problem
4. Slight polyneuropathy
5. Neurography: Low ampl CMAP
If the CMAP of ADM and APB have an amplitude < 2mV , sensory signals OK
which is a likely reason
1. CTS
2. LEM
3. Technical problem
4. Slight polyneuropathy
6. 52Neurography: ? CTS
Your patient has numbness of dig I,II and low sensory signals from Dig I-III but normal
CMAP amplitude
Normal latency from APB and normal sensory signals from dig V.
A likely diagnosis is:
1. CTS
2. radiculopathy
3. polyneuropathy
4. anterior interosseus syndrome
7. 52Neurography: ? CTS
Your patient has numbness of dig I,II and low sensory signals from Dig I-III but normal
CMAP amplitude
Normal latency from APB and normal sensory signals from dig V.
A likely diagnosis is:
1. CTS
2. radiculopathy
3. polyneuropathy
4. anterior interosseus syndrome
Usual that sensory findings are abnormal while motor is preserved I CTS.
Radiculopathy normal SNAP
Not pnp, see ulnar SNAP
Anterior inteross, is motor
8. E2 positions
1
Which is the optimal position for E2 in study of these muscles
Deltoideus
Trapezius
Biceps brachii
´Tibialis anterior
9. E2 positions
1
Which is the optimal position for E2 in study of these muscles
Deltoideus
Trapezius
Biceps brachii
´Tibialis anterior
Acromion/Sternum,
Acromion
Acromion
Patella
14. 4,7/5,6; 19%
71317
2,0/3,9; 49%
If dist CMAP is lower than proximal with Median nerve
stimulation, what to think of
1
Reduction by
Think of M-G
15. 4,7/5,6; 19% reduction
71317
2,0/3,9; 49% reduction
If dist CMAP is lower than proximal in Median nerve
stimulation, what to think of
1
Good routine to superimpose traces
16. 8.93, 8.45 mV
13,2 and 11,2 mV
Ampl decay 15%
Dispersion =0%
Is this significant conduction block? Median nerve
1
If ampl drops > 20%, with little
increase in duration, check for
conduction block
Ampl decay 5%
Dispersion = 15%
17. 8.93, 8.45 mV
13,2 and 11,2 mV
Ampl decay 15%
Dispersion =0%
Is this significant conduction block? Median nerve - NO
1
If ampl drops > 25%, with little
increase in duration, check for
conduction block
Ampl decay 5%
Dispersion = 15%
Uppsala values
Arm: >25% decay and <15% dispersion
Leg:
Fibular nerve >30% decay and <30% dispersion
Tibial nerve > 55% decay and <45% dispersion
18. 52Neurography: ? CTS
Your patient has numbness of dig I,II and low sensory signals from Dig I-III but normal
CMAP amplitude
Normal latency from APB and normal sensory signals from dig V.
A likely diagnosis is:
1. CTS
2. radiculopathy
3. polyneuropathy
4. anterior interosseus syndrome
19. 52Neurography: ? CTS
Your patient has numbness of dig I,II and low sensory signals from Dig I-III but normal
CMAP amplitude
Normal latency from APB and normal sensory signals from dig V.
A likely diagnosis is:
1. CTS
2. radiculopathy
3. polyneuropathy
4. anterior interosseus syndrome
Usual that sensory findings are abnormal while motor is preserved I CTS.
Radiculopathy normal SNAP
Not pnp, see ulnar SNAP
Anterior inteross, is motor
20. 53Neurography: Root or plexus
Patient 80 yo, with right-sided weakness and numbness in the leg.
Low sensory amplitude in right fibularis superficialis but normal on the left side.
Reduced CMAP ampl in right EDB
EMG in Tib ant shows denervation. EMG in lumbar paraspinals normal
1. L5 root
2. plexopathy
3. central lesion
4. polyneuropathy
21. 53Neurography: Root or plexus
Patient 80 yo, with right-sided weakness and numbness in the leg.
Low sensory amplitude in right fibularis superficialis but normal on the left side.
Reduced CMAP ampl in right EDB
EMG in Tib ant show denervation. EMG in lumbar paraspinals normal
1. L5 root
2. plexopathy
3. central lesion
4. polyneuropathy
Normal sensory and paraspinal EMG favors plexus lesion
22. 54EMG: Myasthenia?
Patient with ptosis but no arm or leg weakness. RNS in nasalis and deltoid normal.
SFEMG in orb oculi shows jitter and some blocking. Jitter abnormal in Ext dig.
1. Ocular MG
2. Generalized MG
3. Myopathy
4. Miller Fisher syndrome
23. 54EMG: Myasthenia?
Patient with ptosis but no arm or leg weakness. RNS in nasalis and deltoid normal.
SFEMG in orb oculi shows jitter and some blocking. Jitter abnormal in Ext dig.
1. Ocular MG
2. Generalized MG
3. Myopathy
4. Miller Fisher syndrome
MG classification is conventionally defined on clinical grounds.
Jitter is abnormal in ED in 60% of cases with Ocular MG
24. EMG: Myasthenia?
Patient with bilat ptosis but no arm or leg weakness. RNS in nasalis and deltoid normal.
SFEMG in orb oculi and frontalis normal.
1. Ocular MG
2. Generalized MG
3. Myopathy
4. Bell palsy
25. EMG: Myasthenia?
Patient with bilat ptosis but no arm or leg weakness. RNS in nasalis and deltoid normal.
SFEMG in orb oculi and frontalis normal.
1. Ocular MG
2. Generalized MG
3. Myopathy
4. Bell palsy
Normal SFEMG findings are strong indications that symptoms are NOT due to MG. In this case, it may be
a myopathy, often with very little of jitter abnormalities
26. If the MCV in ulnar nerve across the
elbow is slower (diff > 10 m/sec) than
distally, what to do?
1
27. SSS = motor short segment study, bilateral
US
1
If the MCV in ulnar nerve across the
elbow is slower (diff > 10 m/sec) than
distally, what to do?
29. Median nerve. If the CV is 85 m/sec, what do you
expect?
A combination of Martin-Gruber anastomosis and CTS
1
30. If the sensory median amplitudes are high
(1.8 SD) and the sensory latency
prolonged, what to do?
1
31. If the sensory median amplitudes are high
(1.8 SD) and the sensory latency
prolonged, what to do?
Warm the hands
1
32. Which are the movement responses for
fibular and tibial nerve stimulation
1
33. Which are the movement responses for
fibular and tibial nerve stimulation
• Superficial fibular nerve – eversion of the foot and plantar flexion
• Deep fibular nerve – dorsiflexion, eversion
• Tibial nerve, plantar and toe flexion, inversion
1
34. In a slight CTS the orthdromic latency
from the palm to wrist may be normal but
abnormal from dig III to wrist. Why?
1
35. Predominantly sensory CTS. Palm stim includes motor nerve fibers,
which now give normal latency, hiding the sensory component
1
In a slight CTS the orthdromic latency
from the palm to wrist may be normal but
abnormal from dig III to wrist. Why?
36. 7 different sets of signals from various muscles are shown in the
following slides. Within each example the recordings come from
different patients. Where are the recordings obtained?
A B
5 ms
5 mV
5 ms
5 mV
1
37. Q 22. Different signals will be shown here. Within each example
the recordings come from different patients. Where is the
recording obtained?
A B
5 ms
5 mV
5 ms
5 mV
1
APB ADM
48. 5 ms
5 mV
sensory Usually you cannot tell the origin
of sensory recordings
1
Signals from Sensory nerves, ortodromic or antidromic.
Which nerves?
49. 5 ms
5 mV
sensory Usually you cannot tell the origin
of sensory recordings
1
Cannot tell
Signals from Sensory nerves, ortodromic or antidromic.
Which nerves?
50. In your patient with suspected PNP, the sural
response is only questionably present. You have
ruled out technical errors.
What is the most informative procedure for correct
interpretation now?
check sensitivity in sural area?
check the sural response on the contralateral side
reduce stim-rec distance
test of radial sensory responses
test F-responses in the tibial nerves
Sural SNAP
51. In your patient with suspected PNP, the sural
response is only questionably present. You have
ruled out technical errors.
What is the most informative procedure for correct
interpretation now?
check sensitivity in sural area?
check the sural response on the contralateral side
reduce stim-rec distance (low ampl due to temporal
dispersion will increase)
test of radial sensory responses
test F-responses in the tibial nerves
Sural SNAP
If the amplitude increases with shortening of the
distance = low ampl is due to dispersion (demylin pnp).
If the amplitude is mainly unchanged, axonal loss.
The original low amplitude values with correct
distance goes to report, but an extra comment is
acknowledged
52. Methods of choice
Which is the EDX method of choice for the following diagnostic questions
MG RNS
SFEMG
CTS EMG of APB and ADM
antidromic sensory neurography
GBS EMG
neurography
thermotest
Root EMG
neurography
evoked potentials
ALS EMG
neurography
motor unit counting
53. 59Methods of choice
Which is the EDX method of choice for the following diagnostic questions
MG RNS
SFEMG
CTS EMG of APB and ADM
antidromic sensory neurography
GBS EMG
neurography
thermotest
Root EMG
neurography
evoked potentials
ALS EMG
neurography
Motor unit counting
54. Thumb abduction weakness
After trauma, my patient cannot abduct his thumb
Among the following alternatives to next step, which 2 are the most important?
measure distal latency to APPB
measure sensory latency to/from dig III
watch thumb movements at median stimulation at the wrist
perform EMG in APB
stimulate ulnar nerve with APB recording
55. Thumb abduction weakness
1. It is a rule of good practice to observe the movement of appropriate
muscle at nerve stimulation in all neurography tests.
2. Think of tendon rupture if interference pattern is reduced due to low firing rates
After trauma, my patient cannot abduct his thumb
Among the following alternatives to next step, which 2 are the most important?
measure distal latency to APPB
measure sensory latency to/from dig III
watch thumb movements at median stimulation at the wrist
perform EMG in APB
stimulate ulnar nerve with APB recording
Diagnosis: tendon rupture
56. Voluntary activity and CMAP
1
Is voluntary activity influencing the CMAP amplitude
at supramaximal stimulation, other than effects of muscle shortening
57. Voluntary activity and CMAP
1
Is voluntary activity influencing the CMAP amplitude
at supramaximal stimulation, other than effects of muscle shortening
No,
1. travelling vol activity is blocked by antidromic pulses
2. active MUPs that have passed the stimulator (influencing the CMAP a little)
are refractory when the nerve is stimulated. No addition to the shape.
Note than muscle shortening will increase the ampl.
58. Sometimes you see complex late components after each CMAP at consecutive stimulations. Is
this CMAP satellites (stable) or extradischarges after the CMAP (eg.cholinergic, variable)? How
to tell if they are stable or variable?
1
CMAP satellites:
Superimpose a few traces
after 3Hz stim
In this example, -stable
59. Sometimes you see complex late components after each CMAP at consecutive stimulations. Is
this CMAP satellites (stable) or extradischarges after the CMAP (eg.cholinergic, variable)? How
to tell if they are stable or variable?
1
CMAP satellites:
Superimpose a few traces
after 3Hz stim
In this example, -stable
60. Sometimes you see complex and changing (variable) late
components both before and after each CMAP at consecutive
stimulations. What to do?
1
61. Sometimes you see complex and changing (variable) late
components both before and after each CMAP at consecutive
stimulations. What to do?
Have the patient to Relax
1
62. 5 ms
5 mV
1
Q8.
If CMAP of the EDB is lower at distal than at prox stim,
what to do?
63. Stimulate behind the ankle, anomalous innervation
5 ms
5 mV
dist
prox
+36%
1
Q8.
If CMAP of the EDB is lower at distal than at prox stim,
what to do?
64. Q9. If CMAP amplitude has an unexpectedly
low amplitude (no nerve damage, no pnp),
what to do?
1
65. 1. Stim strength?
2. Check stimulator
3. Check rec and ground
4. Skin condition (thick, lotion)
-----------
1. Measure Ampl change after 10 sek of max vol
activation (LEM)
2. Test other nerves; general or local?
3. Anomaly (M-G, accessory fibular)
Q9. If CMAP amplitude has an unexpectedly
low amplitude (no nerve damage, no pnp),
what to do?
1
66. 1
Q 12. We have different “disturbances” in recording
of the CMAP. Give at least 4 examples
67. Q 12. We have different “disturbances” in recording
of the CMAP. Give at least 4 examples
1. Noise comes from equipment (amplifiers)
2. Interference 50 or 60Hz
3. Wavy baseline; bad grounding, equipment, background
activity from distant voluntary activity
4. Vol cond is generated by remote muscle. If irregular,
vol activity from remote muscle (see 3). If constant,
volume conducted activity from remote muscle
5. Standing wave, non-propagated field (far field
potential)
1
68. Q 18. Can an A-wave appear with longer
latency than the F-responses. If so, where
is it generated?
1
69. Q 18. Can an A-wave appear with longer
latency than the F-responses. If so, where
is it generated?
• The A-wave is produced in an abnormally slow
conducting axon therefore so late
• Still generated in the peripheral nerve
1
70. Could 2 A-waves, seen on the same trace,
generated in the same axon?
1
71. Could 2 A-waves, seen on the same trace,
generated in the same axon?
1
Very unlikely, since the antidromic pulse, triggering the most distal A-wave,
is probably not travelling further in proximal direction to cause a new A-wave
If the same axon gives 2 A-waves, they should be identical in shape
72. Why is it essential to have standard
interelectrode distance for sensory recordings?
1
73. Recordings with different inter-electrode distances
Winkler, Stålberg, Haas, M&N 1991
Short distance (or time along electrode) gives low ampl.
Max ampl when neg peak of first signal coincides with first posivet pek of the second signal
Longer intervals give complex shape.
74. dist
11mV 4mV 36%
2.4 mV 1.3 mV 50%
prox
AH-big toe
big toe - remote
AH- remote
calc 3-2
Motor studies; recording from “AH”, what is
that?
1
75. dist
11mV 4mV 36%
2.4 mV 1.3 mV 50%
prox
AH-big toe
big toe - remote
AH- remote
calc 3-2
Motor studies; recording from “AH”, what is
that?
1
76. For motor studies, how does the size of the
surface electrode influence the recorded signal?
1
distal
middle
proximal
Signals are larger with small electrodes
77. Q27. For motor studies, how does the size of the
surface electrode influence the recorded signal?
1
distal
middle
proximal
Signals are larger with small electrodes
78. Facial nerve has no sensory skin
innervation to the face.
Why is then surface stimulation in the
face painful
1
79. Facial nerve has no sensory skin
innervation to the face.
Why is then surface stimulation in the
face painful
We also stimulate the trigeminal nerve terminals in the skin at the
stim point. This is not the case if we use near nerve needle
electrodes for stimulation
1
80. How do you interpret a finding of low sensory amplitude at
dig III after antidromic testing both at wrist and a palm
stimulation. Ulnar sensory from palm is normal
81. How do you interpret a finding of low sensory amplitude at
dig III after antidromic testing both at wrist and a palm
stimulation. Ulnar sensory from palm is normal
7
7
If the Med nerve is
locally degenerated,
the distal amplitude
will be reduced
82. Q 44. A waves and Repeaters
What is the difference?
A wave Repeater F wave
> 6/20 times 6 or less times/20
Any latency; before,
at or after F
Within F latencies
Explanation
A wave is a MUP
generated focally in
the axon
Repeater F wave is a
MUP generated in the
motor neurone 82
83. Q 44. A waves and Repeaters
What is the difference?
A wave Repeater F wave
> 6/20 times 6 or less times/20
Any latency; before,
at or after F
Within F latencies
Explanation
A wave is a MUP
generated focally in
the axon
Repeater F wave is a
MUP generated in the
motor neurone 83
84. F waves are usually normal in C8 radiculopathy
What about in ulnar lesion at the elbow?
85. F waves are usually normal in C8 radiculopathy
What about in ulnar lesion at the elbow?
Ulnaris abnormal side Ulnaris normal side
86. Late components in a patient witt PLS - ALS
64185
Are these late responses normal?
If not, what are they?
Is there a trick to help understanding?
87. Late components in a patient witt PLS - ALS
64185
Are these late responses normal?
If not, what are they?
Is there a trick to help understanding?
They are not Repeaters, not identical
Probably H-reflexes ,
so reduce stim strength and see the CMAP
disappear while these late responses remain
colntinue
88. Late components in a patient witt PLS - ALS
64185
Thus, these late signals are
H-reflexes (no CAMP)
89. NCS in motoneuron diseases
Which are the main indications for NCS in ? MND
1
90. NCS in motoneuron diseases
Which are the main indications for NCS in ? MND
1
To find:
pnp
sensory neuropathy
motor neuropathy
MMN
entrapment
CMAP amplitudes
press again
91. 58EMG: acute weakness
Patients with acute weakness since 2 days.
If this is GBS, which combination of findings do we get
1. normal CMAP and CV – normal MUPs and firing
2. normal CMAP ,CV – normal MUPs and abnormal firing pattern
3. Reduced CMAP ampl - first signs of denervation
4. Recured # F waves, presence of A waves - abnormal firing pattern in EMG
92. 58EMG: acute weakness
Patients with acute weakness since 2 days.
If this is GBS, which combination of findings do we get
1. normal CMAP and CV – normal MUPs and firing
2. normal CMAP ,CV – normal MUPs and abnormal firing pattern
3. Reduced CMAP ampl - first signs of denervation
4. Recured # F waves, presence of A waves - abnormal firing pattern in EMG
93. The CMAP from APB has an initial positive deflection at proximal but
not at distal stimulation
1 why
2 where do you set the latency cursor?
1
94. The CMAP from APB has an initial positive deflection at proximal but
not at distal stimulation
1 why
2 where do you set the latency cursor?
1
95. Because of amplifier and electrode
characteristics, low amplitude signals such as
SNAPs will be disturbed by noise. This will
influence accurate measurements. How can
we reduce the noise? Give 3 answers.
.
1
96. Because of amplifier and electrode
characteristics, low amplitude signals such as
SNAPs will be disturbed by noise. This will
influence accurate measurements. How can
we reduce the noise? Give 3 answers.
.
• Skin and recording contact
• Filter (3KHz instead of 10KHz)
• Averaging
1
97. Is it commendable to change polarity of the
stimulator for F-wave studies
1
98. Is it commendable to change polarity of the
stimulator for F-wave studies
1
No, the cathode is much stronger stimulator than the anode and there is
no anodal block at “normal” stimulation strength
99. Fasculations and F waves
Can spontaneous Fasciculation potentials generate F waves?
100. Fasculations and F waves
Can spontaneous Fasciculation potentials generate F waves?
Yes. Wait for one minute recording in a muscle with fasculation potentials,
and you will often see one of them firing twice with an interval corresponding
to F wave latency for that muscle, and with same shape
101. F waves in st. post polio and myopathy
Describe the principle difference between F wave characteristics in these two conditions
102. F waves in st. post polio and myopathy
Describe the principle difference between F wave characteristics in these two conditions
The single F-response is = surface recorded MUP
Therefore
Neuropathy: high amplitude F waves (reinnervation and low persistence (loss of axons)
(Note there is a relationship between CMAP amplitude and F persistence in neuropathies)
Myopathy: low amplitude and normal persistence (note that persistence includes an amplitude
definition, so, some F responses may be undetected, giving an “falsely” low persistence)
