MUSCLE biopsy is intentionally done hours to a few days after the electromyographic (EMG) examination and in the same region of muscle in some clinics, with the hope of determining the muscle pathology responsible for the electrical responses. At many other institutions, the order of EMG and muscle biopsy is indifferent, as is the relationship of the sites of the two procedures. When evaluating reports of subtle histologic abnormalities of muscle in patients also thoroughly studied by EMG which do not mention time and geographic relationships of these two examinations, it is difficult not to assume such indifference. It is, therefore, pertinent to emphasize that focal myopathic changes can be produced by EMG and hypodermic needles. The practical implication is that a muscle biopsy must not be taken from a previously needled site. Conversely, EMG or hypodermic needling must not be done in a site to be biopsied.
W. King Engel. Focal Myopathic Changes Produced by Electromyographic and Hypodermic Needles"Needle Myopathy". Arch Neurol. 1967;16(5):509–511. doi:10.1001/archneur.1967.00470230061008