Clinical significance of vertical component of caloric response including its second phase in vertiginous patients

Up-beating vertical component recorded in the caloric first phase was attributed mainly to the inhibitory endolymph flow in the anterior canal. Down-beating vertical component recorded in the caloric second phase provoked by a positional change could be explained by a reversed endolymph flow in vertical canal(s).

To investigate the origin of a vertical component in caloric response.

We analyzed electronystagmography (ENG) of caloric responses, which had measurable horizontal component in the caloric first phase in both ears in 200 ears of 100 vertiginous patients. A caloric first phase was provoked by cold water in the supine position with the lateral semicircular canal earth-vertical. A caloric second phase was provoked by re-orienting the lateral canal from the earth-vertical to earth-horizontal after the cessation of the first phase (provoked second phase). The nystagmus of the whole procedure was recorded by two-dimensional ENG.

We recorded the vertical component in 103/200 ears in the caloric first phase, which was directed mostly upward (92/103 ears). We also recorded the vertical component in 91/200 ears in the provoked second phase, which was directed almost exclusively downward (90/91 ears).