Normal values for single fiber EMG parameters of frontalis muscle in healthy subjects older than 70 years

Abstract

Objective Single fiber EMG (SFEMG) is a potent electrophysiological method to evaluate impaired neuromuscular transmission, and allows sensitive diagnosis of neuromuscular transmission abnormalities such as myasthenia gravis. The jitter and fiber density values are different for various muscles and age groups and the reference values increase with age. In this study, we evaluated the reference values of jitter and fiber density of frontalis muscle in healthy subjects older than 70 years. Methods We evaluated the jitter and fiber density of frontalis muscle in 32 healthy subjects. Twenty-two of them were between 70 and 79 years old (mean±SD, 73.9±1.7), and 10 of them were older than 80 years (mean±SD, 82.2±1.2). Results Normal limit of jitter (95% confidence limit) was calculated as 40.4 μs for healthy subjects between 70 and 79 years old and 43.7 μs for healthy subjects older than 80 years and normal limit of fiber density (95% confidence limit) were calculated as 1.90 for subjects between 70 and 79 years old and 2.14 for subjects older than 80 years. Conclusions We designated the reference values of jitter and fiber density for frontalis muscle in healthy subjects older than 70 years. Our reference values may have value to diagnose neuromuscular transmission abnormalities in elderly patients. Significance SFEMG is sensitive for neuromuscular transmission abnormalities and it is important to know the reference values of frontalis muscle in healthy subjects older than 70 years.