Amyotrophic Lateral Sclerosis

Touch MEdical MEdia 53 Fasciculation, which is observed in various peripheral motor neuron disorders, is most frequently found in nonprogressive benign fasciculation syndrome (BFS). Patients with BFS never exhibit muscle atrophy or pathologic weakness and not all such patients visit hospitals; therefore, the prevalence and characteristics of BFS still need to be established. However, among the progressive disorders involving motor neurons, amyotrophic lateral sclerosis (ALS), progressive muscular atrophy, and other motor neuron diseases such as Kennedy disease, seem to be the most frequent disorders that show overt fasciculation. In ALS, especially, fasciculation is often noted before patients recognize atrophy or weakness. Acquired neuromyotonia (Isaacs’ syndrome) also shows overt fasciculation and myokymia mimicking ALS. It is often difficult to establish a definite diagnosis of ALS, BFS, or other generalized disorders when patients complain of only fasciculation; in such cases, electrophysiological examinations, including needle electromyography (EMG) and nerve conduction study, are necessary and useful.