Muscle ultrasonography in diagnostics of fasciculations: A lot has been done, but there is still more to do

Abstract

Fasciculations are involuntary twitches of small parts of the muscle with a duration of 0.2-1.0 s due to spontaneous contraction of muscle fascicles. These twitches originate from motor unit depolarizations. In terms of recording by electromyography (EMG), fibrillation potentials are spontaneous action potentials of denervated muscle fibers. [1][2][3] Fasciculations are associated with excitability changes in both lower motor neurons and upper motor neurons. 1,4 Widespread fasciculations are strongly characteristic of amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease). However, fasciculations are not exclusively specific to ALS.Fasciculations occasionally occur in healthy individuals (benign fasciculations) and individuals with diseases other than ALS (including metabolic disorders) and different lower motor neuron diseases. 5 Electrophysiological confirmation is necessary for ALS diagnosis. For many years, the "El Escorial" diagnostic criteria were used. These criteria exhibit high specificity but low sensitivity, ranging from 18 to 53%. 6 Recently, Ma et al compared ultrasound (US) with EMG examina-