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NMES for nerve transfers?

I have a patient with neurotization of the deep peroneal nerve with tibial nerve (with a graft from n.suralis). This is the first time I try to stimulate a muscle with nerve transfer which shows reinervation on EMG. So when I put the electrodes on the tibialis anterior muscle there is palpable twich of the stimulated muscle, but the patient gets strong contraction by the muscles innervated by the tibial nerve (e.g. tibialis posterior). I assume that this is because of the neurotiation though it strange how this stimulation goes somewhat "backwards". So my question is is there anyway to avoid that , or is it normal, or any other ideas and reccomendations. The patient is able to voluntary contract tibialis anterior muscle though there is only palpable and small visible twitch. Thank you in advance.

Georgi Petrov

5 months ago

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gvpetrov223
gvpetrov223

Yeah Dr. Nussbaum, that was my explanation also, just it was strange how through a stimulation of tibialis anterior you get a strong contraction of muscles that are located on a completely different place (e.g. tibialis posterior which is separated from the tibialis anterior with a bone). So I was wondering is it the depth of the penetration of the current responsible for that, or some strange phenomenon of the neurotization or something else. Because for example if you stimulate the thenar muscles (n.medianus) usualy you don't get contraction of the long finger flexors (also n.medianus, but located proximaly). Hope that this example explains what I was wondering.

Prof Tim Watson
Prof Tim Watson

Thanks for that Ethne - makes a whole lot of sense

Dr Ethne Nussbaum
Dr Ethne Nussbaum

What you describe makes sense to me. When you were using 1000 ms pulses, presumably with a slowly rising amplitude, the normally innervated muscles were not responding due to normal nerve accommodation to slowly rising stimulus. At the same time, the denervated muscles were being stimulated directly, i.e. not via motor nerve but actually the muscle fibres themselves. Recall that muscle fibres are not very excitable and do not accommodate to slowly rising stimuli. Now that you are using a short duration, rapidly rising wave form, it is to be expected that normally innervated muscles in the area will respond. The higher you increase amplitude to try & activate tib anterior the greater the overflow of current you will cause to nearby muscles. At this stage you may have few innervated tib ant fibres - so a twitch is all you can see. As more tib ant motor units come into play you will see a larger contraction. My experience in some adolescents (axillary nerve, radial nerve) is that the nerve transfers sadly were never entirely successful in that the number of active motor units was insufficient to produce functional activities. For your present patient I would suggest that with continuing recovery you may be able to stimulate a greater number of tib ant motor units at lower amplitude - that will eliminate the overflow to unwanted muscles

gvpetrov223
gvpetrov223

Well, first of all this patient is a kid - 7-8 years old (if that is important). He had his peroneal nerve "damaged" by some benign tumour. After that he had this neurotization performed because the nerve was not in a good condition (I had to check in the records about the details if that is important). In our first meeting (January) there was no reinnervation of the muscles so I was using rectangular pulses with 1000ms lenght (they are preprogrammed in the machine (Genesy 1500 by Globus Corporation, Italy), for denervated muscles). During this stimulation there was proper contraction of the muscle. Some two months after that there was EMG sings of reinervation so we tried NMES. The exact parameters I should check because I used again programs from the machine, but it uses biphasic symetric pulses and the freq is in the range 30-50 Hz (I am not shure about the pulse width and should check the amplitude that we reached in the records), and something like 10 seconds contrction, 20 seconds rest. Basicly I tried various positions of the electrodes - at the two ends of the muscle (tibialis anterior), one in the middle/one on the distal part, a bit left , a bit right , etc., with more or less the same result. I was using 5 cm square electrodes. Then I stopped because I was not shure what is going on. Hope this story helps. When he comes again (he lives in a different city but comes because our surgeon is the most famous in the country) I will make a video if he agrees.

Prof Tim Watson
Prof Tim Watson

this is interesting - though not something that I have experienced personally. There may be others who have direct experience, but while we are waiting, can you tell us where your electrodes were placed for this patient? and the stimulation parameters. Thank you

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