Quantitative EMG (qEMG)
After recently investing in eight new Cadwell NCS/EMG beta software systems, which are shared with the Mayo Clinic in the USA, we are now able to perform qEMG in our Southport clinic.
The EMG is first performed instantaneously using visual, qualitative (analogue) methods to distinguish normal from abnormal motor units and analyse patterns indicating specific diseases.
qEMG data is then analysed and re-played offline, allowing for more detailed analysis of the sampled motor units from the EMG. Using qEMG, several parameters can be derived, providing reliable information about the neurological state of the muscle (neurogenic, myopathic or normal). When using qualitative methods alone, the examiner must infer all of this information in a very short period of time. (Imagine reporting on a CT scan in only seconds!)
qEMG also allows for the vigilant analysis of multiple individual motor unit potential (MUPs) from the one muscle; whereas qualitative methods rely heavily on the presence of one or a small number of abnormal potentials.
Another parameter that can now be analysed using qEMG is the Interference Pattern (IP), which is the sum of multiple MUPs firing simultaneously during maximal voluntary contractions. This is vital in determining if a muscle is pathologically myogenic.