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Which muscle?
This is an ordinary fibular nerve motor conduction study recorded from EDB. The CMAP responses to ankle and fibular head stimulations were perfectly fine (top two traces (see attached). However, the popliteal fossa stimulation resulted in a double peaked CMAP (the third trace) with lowered peak amplitude. I think it is from a tibial muscle (due to coactivation/costimulation of tibial motor nerve). The question is which muscle is responsible for the extra peak? Thanks.
p. s. I don't want this to turn into discussion of volume conduction of the stimulation. There is no conduction block. Needle stimulation was later used and a perfectly matching CMAP morphology as the top two traces was obtained.
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