Comparison between ultrasound and electromyography for detection of fasciculations in amyotrophic lateral sclerosis: an updated systematic review and meta-analysis.

Fasciculations are a key manifestation of lower motor neuron dysfunction in amyotrophic lateral sclerosis (ALS). Al-though electromyography is considered the gold-standard method for the detection of fasciculations, its sensitivity for that purpose depends on the muscle sampled and the examination time. Muscle ultrasound has emerged as a dynamic, noninvasive technique with high sensitivity for detecting spontaneous muscle activity. This updated system-atic review compares ultrasound and electromyography in terms of their performance for the detection of muscle fas-ciculations in ALS, with stratification by muscle group and observation time. A comprehensive search of the literature identified studies evaluating both techniques. Data were synthesized descriptively and, when possible, quantitatively. Ultrasound demonstrated higher or comparable detection rates across most muscle groups, particularly in muscles that are large or deep, such as the biceps brachii, tibialis anterior, and vastus lateralis. Longer ultrasound observation times, especially 60 s, were associated with substantially higher detection rates without a loss of specificity. Although electromyography is still essential for electrophysiological characterization, ultrasound offers broader muscle cover-age, excellent reproducibility, and a noninvasive approach. These findings support muscle ultrasound as a valuable complementary tool for the detection and assessment of fasciculations in patients with motor neuron disease.