" Clustering Index method": A new technique for differentiation between neurogenic and myopathic changes using surface EMG

Objective: To establish a non-invasive and quantitative analysis method using single-channel surface EMG (SEMG) for diagnosing neurogenic and myopathic changes. Methods: The subjects consisted of 66 healthy controls, 12 patients with neurogenic diseases, and 18 patients with myopathic diseases. The tibialis anterior muscle was examined using a belly to the adjacent bone lead. From each subject, 20-40 signals of 1. s length were collected of various strengths. A new parameter, the " Clustering Index (CI)" , was developed to quantify the uneven distribution of the SEMG signal, and was plotted against the SEMG area. The results were expressed as the Z-score of each subject calculated using linear regression from the normative data. Results: When ±2.5 was used as the cut-off value of the Z-score, the specificity was 95%, whereas the sensitivity was 92% (11/12) and 61% (11/18) for the neurogenic and myopathic patients, respectively. There was no overlap of the Z-score values between the neurogenic and myopathic groups. Conclusions: The CI method achieved a reasonably high diagnostic yield in detecting neurogenic or myopathic changes. Significance: This is a new simple and quantitative analysis method using SEMG with good reproducibility, and is promising as a non-invasive complement to needle EMG.