Complex Fasciculation Potentials in Amyotrophic Lateral Sclerosis

Abstract

Fasciculation and fasciculation potentials (FPs) are most frequently observed in progressive motor neuron disorders, including amyotrophic lateral sclerosis (ALS). Recent diagnostic criteria, the so-called Awaji criteria, emphasize the importance of FPs in the electrodiagnosis of ALS. Although FPs are found in other benign syndromes, FPs in ALS often show a complex morphology (complex fasciculation potential [CFP]) with instability in the form of increased jitters with blocking of some components of the FPs. The criteria have raised the diagnostic significance of FPs as FPs have clinical importance in the diagnosis of ALS equivalent to spontaneous denervation potentials (fibrillation potentials and positive sharp waves). CFPs have multiple pathomechanisms, but they frequently originate from the most distal sites of the peripheral motor neurons. In addition, CFPs are strongly related to axonal membrane hyperexcitability. The increased amount of CFPs in individual patients has been reported to predict shorter survival and rapid progression of the disease. These findings suggest that CFPs have a disease-specific significance to ALS; therefore, exact documentation of CFPs in needle electromyography may contribute to correct diagnoses of ALS and early clinical trials.