Correlation between tremor parameters.
The relationship between clinically scored tremor and electromyographic measurements of tremor amplitude is not clear and few reports have examined correlations between different tremor parameters. The aim of this study was to evaluate the correlations between different tremor parameters, clinical tremor scoring, age and disease duration. A total of 525 patients with different types of tremor were included in this study. Tremor in various limb positions was graded according to the Webster Tremor Scale. Surface electromyographic recordings of the limb found, in each position, to be most involved were performed in all the patients. The Spearman rank correlation coefficient was used to analyse the relationship between clinical and electromyographic parameters, while the Pearson correlation coefficient was used to analyse the relationship between the electromyographic parameters. Our results revealed moderate correlation between tremor amplitude as measured by electromyography and Webster tremor scores. The correlation between different tremor parameters revealed that low frequency tremors have higher amplitude, and longer burst duration, interval between bursts and missing interval. As the disease progresses, the tremor amplitude increases, while the frequency decreases. A strong positive correlation emerged between corresponding tremor parameters in different limb positions. This suggests that the tremor in all limb positions is generated by the same oscillator. In conclusion, a good correlation was found between clinically scored tremor and EMG measurements of tremor amplitude. The electromyographic examination is a useful tool for researching tremor mechanisms.