[Methodology and diagnostic possibilities of macro-EMG. II. Diagnostic possibilities]

The macro-EMG can be recorded with a modified single fiber or concentric needle. The two needles attain different results with smaller potentials values for the concentric needle type. For the single fiber type normal data are given for the EDC and tibialis anterior muscle. These data are compared with previously published results and their statistical evaluation. The concentric needle type can be used for scanning EMG. In addition potential stability can be examined in different parts of the MU using the unblanketing principle. A further novel use for macro-EMG is simultaneous single motor unit twitch recording to compare mechanical and electrical MU activity. In normal muscle the electrical signal is positively correlated with twitch force. In diseased muscle like ALS twitch is dissociated from electrical potential size. Macro-EMG allows to quantify MU size, a prerequisite to follow up dynamic changes in muscle. Improved computer programs in commercially available EMG-machines will help to introduce this method into clinical EMG laboratories as a useful addition to increase the diagnostic yield of EMG.