[Quantitative analysis of electromyogram interference pattern in extraocular muscle]

Quantitative analysis of electromyogram (EMG) interference pattern was performed for objective evaluation. EMGs of 261 horizontal rectus muscles had been recorded in our laboratory during the past 18 years, and they were divided according to the clinical diagnosis into four categories: 56 records due to complete neuropathy, 67 due to incomplete neuropathy, 19 due to myopathy, and 119 normal. The turns and amplitude analysis program was used for EMG analysis. A turn was one wave of the interference pattern, for which we used an amplitude of more than 15 microV. Turns meant the number of turn waves per second. Turns/second and mean amplitude/turn (A/T) were plotted against each other on an X-Y diagram, and a statistical evaluation of data was done. Complete neuropathy recordings that had lower turns and lower A/T were separated from the other three categories. Incomplete neuropathy and myopathy occurred on the lower A/T area. There was a significant difference (p < 0.05) between each pair of comparisons from all four categories except for turns evaluated between myopathy and normal. Quantitative analysis proved useful for the objective evaluation of the EMG interference pattern, particularly between cases of complete and incomplete neuropathy.