CNE Jitter method

1. Jitter recordings with
concentric needle electrode
Erik Stålberg
Most of the voluntary signals are recorded by Stålberg
All stimulation signals are recorded by Kouyoumdjian (shown with permission)

2. Filter: SFEMG 500Hz-10KHz
CNE for jitter analysis 1KHz-10KHz
Sweep speed: 0,5 msec/div (always less than 2 msec/div)
Gain: not crucial. Make signals to cover about 2 divisions
For quality control during and after recording, superimpose 5-
15 sweeps.

3. Definitions of acceptable CNE signals
for jitter analysis
Monotonously rising positive negative signals without inflections, notches or shoulders.
Parallel rising segments upon superimposition (5-15)
(Slight disturbance, e.g. influence from remote fibers, can be accepted if it occurs close to
the positive peak, lower than 50% of rise time)
Negative peaks should be separated by more than 150 usec
Only slight amplitude variation in the signal, else summation from same MU or background
activity
VOLUNTARY ACTIVATION:
Above + Regular firing rate
ELECTRICAL STIMULATION:
Above + supraliminal stimulation intensity

4. Normal
Voluntary

5. Normal
Voluntary

6. Normal
Voluntary

7. Voluntary

8. Looks like impulse blocking at traces with arrows. This is not so,
but false trigger. The large signals on these traces have another
shape (broader, higher) than the neighbours
Normal
Voluntary

9. The first spike obviously composed of 2 fibers. It it still accepted, since the disturbacance
is near the positive peak and most likely gives only minor influence to the jitter value.
Normal
Voluntary

10. Courtesy Kouyoumdjian
Surface electrode is used for stimulation

11. Stimulation

12. Stimulation

13. Stimulation

14. El stim. Signals with arrow are not accepted; non parallel rising phase or
disturbance in the negative peak, which is used for measurements
Stimulation

15. Stimulation

16. Stimulation

17. Looks OK but see next slide
Stimulation

18. Both signals show non- parallel rising phase. Not used
Stimulation

19. Stimulation
accepted

20. Stimulation

21. Stimulation
Nr 1 accepted

22. Signal nr 2 not used since it has an inflection
above half-way of rise-time
Stimulation

23. Stim CNE MG, Frontalis
Courtesy J Kouyoumdjian

24. Stim CNE MG, Frontalis
Courtesy J Kouyoumdjian

25. Jitter measurements of separated signals :
points crossing amplitude level or peaks
Trig level
Stålberg
start
stop
for signals within
the window
trig
time window
start
time window
stop
Methods for jitter analysis. In the original method, level trigger, time measurements was made between the
moments when the signal passed a predefined amplitude level (time windows, start and stop).
In a more recent method, peak trigger, measurements are made between mathematically calculated negative
peak of each spike (full arrows).
In this example, the spikes are well separated, and the two methods give the same numerical result

26. Jitter measurements of riding signals :
points crossing amplitude level or peaks
Stålberg
Trig level
start
In this fig it is seen that errors in time measurments occur if the signals are “riding” on each other using time
amplitude level method. Therefore peak trigger method is recommended, now available in some EMG equipment.

27. Errors in jitter measurements
Voluntary activation
• Triggering spike
• IPI measures; level or peak
• VRF
• Long IPI (should be < 4 msec)
Electrical stimulation
• Subliminal stimulation
• Irregular freq (stim, F, doublet)
• Axon reflex
Pitfalls in jitter measruements, Stålberg, Sanders, Kouyoumdjian
Clin Neurophysiol, 2017

28. 1_2 1_3 1_4 jSUM
48.8 46.1 94.2 189.1
2_1 2_3 2_4
48.8 34.6 92.2 175.6
3_1 3_2 3_4
46.1 34.6 91.3 172.0
4_1 4_2 4_3
94.2 92.2 91.3 277.7
Different jitter values depending on choice of trigger. A sum of jitter values (jsum) indicates the optimal choice, in this case
trigger on spike 3. Spike 4 not useful because of slow rise-time
ALS
Arrow indicate
chosen trig

29. *
Signals on first 3 traces likely from the same axon. Spikes with arrow and * from 2 other axons

30. 20 µs 45 µs
Right Frontalis
0.5mV/D 0.3 ms/D
13 µs8 µs
A B
20 µs 45 µs
El stim
accepted accepted accepted not accepted
88 µs 13 µs

31. MCD = 150 µs
Supramaximal for some spikes.
Many individual spikes show
independent blocking (arrows)
MCD = 262 µs
Submaximal
Only 1 spike and blocking
This shows how difficult
the interpretation may be

32. 0-2 Hz
0-5 Hz
0-10 Hz
0-15 Hz
0-20 Hz
0-1 Hz
El stim.
Constant stim
intensity
except for
induced
Pauses.
Note the effect of
VRF,particularly at
higher stim
frequencies
Stålberg

33. Axon reflex with distinctly separated latencies
Courtesy Kouyoumdjian

34. Individual blocking in reinnervation;
spikes probably representing different axons
Blocking components behave independently
Courtesy Kouyoumdjian

35. VRF effect seen
after the blocking
of on impulse
Gives a jitter values of
54 usec
Poems disease Courtesy Kouyoumdjian

36. Jitter with CNE
OO vol 31 45
OO stim 27 36
Frontalis vol 28 38
Frontalis stim 21 28
Ext dig vol 30 43
Ext dig stim 24 35
Muscle Mean MCD Individual data
limit µs limit µs
Stålberg et al. Multicenter study, 2016