ABSTRACT
Neurophysiological investigation in amyotrophic lateral sclerosis (ALS) has several roles. The importance of electromyography (EMG) in the diagnosis of this clinical disorder was recognized many years ago, in particular as a consequence of the work of Edward Lambert, who proposed a number of critical findings in EMG investigation to support the clinical diagnosis of ALS. Insertional positive sharp-waves are probably the earliest sign of denervation, but it is difficult to support a diagnosis based on this insecure finding. Fibrillation and positive sharp-waves at rest, which are considered a cardinal sign of denervation, are non-specific findings that can be recorded in myopathies, as well as in neurogenic disorders. Fasciculations are typically observed in ALS and may be its presenting feature. Patients with denervation localized in one region and diffuse FPs should be strongly suspected of having ALS.
