The F wave: Electrodiagnosis and clinical applications

The problem of nerve lesion localization is often difficult, especially when the proximal segment is involved. Determination of motor nerve conduction velocity for the whole length of the nerve, not measurable by conventional methods, can be estimated by F-wave muscle responses. The F-wave is a late muscle response, mainly of the small muscles of the hand and foot, easily elicited by supramaximal stimulation of the nerve. The recording of the F-wave as a diagnostic tool in the localization of nerve lesions has clinical importance in many types of cases. These include compression neuropathies, cervical and lumbar spondylosis, Guillain-Barre syndrome and other neuropathies. Especially in cases with normal motor nerve conduction as determined by conventional methods, the F-wave response should be routinely measured during the neurophysiological examination.