The relative diagnostic sensitivity of different F-wave parameters in various polyneuropathies

Muscle Nerve. 1992 Aug;15(8):912-8. doi: 10.1002/mus.880150808.


We studied F-wave minimum latency, persistence, and chronodispersion in the median and ulnar nerves of 70 controls and 75 patients with various polyneuropathies. Prolonged minimum latency was the most frequent F-wave abnormality in all groups of patients with polyneuropathy. The finding of decreased persistence or absence of F-responses was comparable in sensitivity to prolonged minimum latency in Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), whereas chronodispersion had a comparable sensitivity only in CIDP. Decreased persistence of obtained F-responses, and the absence of F-responses in nerves with low compound muscle action potential amplitudes, were nonspecific findings. F-wave studies often provide useful additional information in the evaluation of patients suspected of having a polyneuropathy. In patients with axonal polyneuropathies, we found that F-wave studies are significantly more sensitive than standard motor conduction studies in identifying physiological abnormalities of motor axons. Furthermore, in a patient with an acquired polyneuropathy, the finding of markedly prolonged minimum latency, or the absence of F-responses in nerves with normal CMAP amplitude, is highly specific for the presence of demyelination.

MeSH terms

  • Adult
  • Demyelinating Diseases / diagnosis*
  • Diabetic Neuropathies / diagnosis*
  • Electrodiagnosis*
  • Humans
  • Median Nerve / physiopathology
  • Middle Aged
  • Neural Conduction / physiology
  • Polyradiculoneuropathy / diagnosis*
  • Reference Values
  • Sensitivity and Specificity
  • Ulnar Nerve / physiopathology