These are some questions mainly for electromyographers.
If you get 50% correct in your answers, you have a good knowledge.
Naturally the answers can always be discussed, but the most reasonable alternative is enough.


1. In routine EMG we usually ask the patient to perform a strong contraction, and the EMG pattern is analyzed.
    Give a few words of argument why each of these descriptions are less than optimal:
  • Interference pattern ?
  • Summation pattern ?
  • Pattern at strong contraction ?
  • Recruitment pattern ?
  Show/Hide Answer

2. Can a MUP have a longer total duration than the interval between discharges of this MUP ?   Show/Hide Answer

3. Is it possible to decide whether a recorded EMG signal originates in the nerve or in the muscle ?   Show/Hide Answer

4. Is there any difference in MUP parameters if the recording is obtained 2 cm or 10 cm from the end-plate?   Show/Hide Answer

5. We sometimes record double discharges (extra discharges) in voluntary EMG. Do we require that the two discharges are identical in shape (amplitude, duration, phases), as a mean to separate them from occasional occurrence of discharges from 2 different MUPs?   Show/Hide Answer

6. Critical illness: are fibrillations usually a sign of neuropathy (CIP)?   Show/Hide Answer

7. Critical illness: is the myosin content lower in CIM than in CIP?   Show/Hide Answer

8. Critical illness: is sural amplitude different in CIM and CIP?   Show/Hide Answer

9. Can an A-wave appear after the F-waves?   Show/Hide Answer

10. Can an A-wave and a F-response be generated in the same axon by a given stimulus (SFEMG necessary to identify the we record from the same axon)?   Show/Hide Answer

11. Is there any difference in amplitudes between A-waves and individual F-responses?   Show/Hide Answer

12. Monopolar recording. Is there any difference in the pattern at strong voluntary contraction if the distance between the two recording monopolar electrodes (“active” and “reference”) is 1 cm or 10 cm?   Show/Hide Answer

13. Can you detect the “size principle” with conventional needle electrodes?   Show/Hide Answer

14. Concentric electrode has an oval recording surface: are the MUP parameters different for transversal or longitudinal insertion of the electrode (in relation to the fiber direction)?   Show/Hide Answer

15. Which is the concentric needle electrode recording uptake radius (180 or 360 degree) for the duration parameter in a MUP?
Which is the concentric needle electrode recording uptake radius (180 or 360 degree) for the spiky part of the MUP?   Show/Hide Answer

16. Is it possible to make sure that you are stimulating muscle fibers directly and not intramuscular nerves in intramuscular muscle stimulation (critical illness tests)?   Show/Hide Answer

17. You may stimulate one or very few axons at two different sites (prox and dist) and record an EMG (or SFEMG) response from corresponding muscle and so measure the conduction velocity in a single axon. How do you ascertain that you have stimulated exactly the same axon?   Show/Hide Answer

18. SFEMG: how many spikes do you need to record simultaneously to detect neurogenic blocking?   Show/Hide Answer

19. SFEMG: how many spikes do you need to record simultaneously to detect neurogenic jitter?   Show/Hide Answer

20. Reinnervation. In the early stage of reinnervation (20-30 days) after a partial nerve lesion, you start to see MUPs with some jittering spikes. In general is the MUP “small” or “large”?   Show/Hide Answer

21. In monopolar EMG recording you often see a small positive going signal on the slow slope of the signal, before it ends. What is this, and why do you not see that in concentric needle EMG?   Show/Hide Answer

22. With increasing force, the EMG amplitude (envelope amplitude) increases. Why?   Show/Hide Answer

23. In concentric needle electrode recordings, one can sometimes obtain low amplitude MUP that looks “upside down”. Explanation?   Show/Hide Answer

24. In voluntary EMG Extra discharges (ED) are often seen (normal) at initiation of activity after a short pause. Where are they generated, muscle, axon, motor neurone?   Show/Hide Answer

25. What is this? Mechanism?   Show/Hide Answer


[1] Stålberg E and L Karlsson. Simulation of the normal concentric needle electromyogram by using a muscle model. Clin.Neurophysiol.:2001;112(3): 464-71.
[2] Stålberg E, et al. Single Fiber EMG (ed. 3rd). Uppsala, Edshagen Publishing House. 2010
[3] Ertas M, et al. Can the size principle be detected in conventional EMG recordings? Muscle Nerve:1995;18: 435-9.
[4] Nandedkar S D, et al. Selectivity of electromyographic recording techniques; a simulation study. Med Biol Eng Comput:1985;23: 536-40.
[5] Nandedkar S D and D B Sanders. Recording characteristics of monopolar EMG electrodes. Muscle Nerve:1991;14: 108-12.
[6] Stålberg E, et al. Electrical microstimulation with single-fiber electromyography: a useful method to study the physiology of the motor unit. Journal of Clinical Neurophysiology:1992;9: 105-19.
[7] Gydikov A and D Kosarov. Extraterritorial potential field of impulses from separate motor units in human muscles. Electromyography Clinical Neurophysiology:1972;12: 283-305.