Clinical and electromyographic examinations of patients with essential tremor

Background: It is believed that no clinical differences exist among essenti al, familial and senile tremor, or between the tremor with synchronous or a lternating electromyographic activity. The aim of this study was to evaluat e the clinical and electromyographic findings in a large group of patients with different types of essential tremor. Methods: Two hundred and twenty p atients with sporadic, familial or senile variants of essential tremor were examined. According to the electromyographic activity recorded from the an tagonistic muscles, the patients were subdivided into a group with synchron ous (SYN) and a group with alternating (ALT) activity. The historical aspec ts of the disease were noted, and a detailed neurological examination was p erformed. Results: A widespread tremor involving upper and lower limbs and 3-4 different anatomical regions was typical for familial tremor. It also h ad higher amplitude than the sporadic and senile tremor. ALT tremor had a h igher amplitude and longer burst duration than SYN and more often involved lower limbs. Rest tremor was common in the ALT group. Overall, ALT tremor w as more common than previously supposed. Conclusion: The familial and ALT t remors are more disabling than other types of essential tremor. Since elect romyographic ALT activity is common in essential tremor, its presence does not reliably distinguish essential and Parkinsonian tremor.