title: [F-waves].
abstract: F-waves result from the discharge of the motoneurons following their antidromic activation. The F-wave appears, as an indirect (the F-wave latency decreases when the stimulation site moves away from the muscular detection) and late response (occurring after the M response). In practice, the most useful parameter is the F-wave minimal latency, provided that at least seven distinct F-waves are evoked. When the analysis is relative either to the controlateral side, or to a former examination, this parameter is one of most sensitive in electroneuromyography. F-wave evocation implies conduction along the entire peripheral nervous system, and particularly its proximal part, which is not investigated by nervous trunks conduction velocity studies. Thus, F wave study is the most useful in plexopathies and polyradiculonevritis. In the early phase of Guillain-Barré syndrome, their absence may be the unique sign indicative of proximal conduction blocks.
authors.affiliation: Service de médecine physique et de l'appareil locomoteur, CHU Sart Tilman, B35, 4000 Liège, Belgique. fc.wang@chu.ulg.ac.be
authors.forename: F C
authors.initials: FC
authors.lastname: Wang
authors.forename: N
authors.initials: N
authors.lastname: Massart
authors.forename: J-F
authors.initials: JF
authors.lastname: Kaux
authors.forename: O
authors.initials: O
authors.lastname: Bouquiaux
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D003711:Demyelinating Diseases / Q000209:etiology / Q000503:physiopathology; D004558:Electric Stimulation / Q000379:methods; D004568:Electrodiagnosis / Q000379:methods; D055724:Electrophysiological Phenomena; D006801:Humans; D016472:Motor Neuron Disease / Q000209:etiology / Q000503:physiopathology; D009046:Motor Neurons / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D012018:Reflex / Q000502:physiology