Cervical vertigo. Diagnostic and semiological problem with special emphasis upon "cervical nystagmus".

There is a strong evidence that vertigo can be produced by cervical disturbance, either via the neck-proprioceptor, or via the vascular supply by the vertebral artery. However, it is very difficult to confirm the cervical origin of the vertigo in a particular patient. "Cervical nystagmus" has been proposed as a diagnostic clue. But critical analysis, discussed in this paper, has raised doubt about its reliability. The most know type, the neck torsion nystagmus, appears to be in fact a "normal" cervico-ocular reflex. Its inconstancy and low gain makes that it is only present in 50% of the subjects. Reduced vestibular input as well as enhanced cervical proprioceptive input favour its appearance. In this way the presence of NTN is suggestive for a cervical component but doesn't mean that the vertigo is cervical. Correlation with other cervical data is needed to conclude to a "cervical component" in the vertigo.