Urea test and vestibular dysfunction in suspected Ménière's disease.

Twenty-four consecutive patients underwent urea testing as part of a diagnostic work-up for vertigo and/or fluctuating hearing loss. Latent and positional nystagmus were evaluated by electronystagmography before and after urea ingestion. Of 10 patients with no nystagmus pre urea, only one exhibited slight latent nystagmus post urea. Of 14 patients with latent or positional nystagmus prior to the urea test, two lost their nystagmus, four showed marked decrease in slow component velocity, and eight were unchanged. No correlation could be made with cochlear response. Direction changing positional nystagmus showed a greater propensity to resolve with urea than did latent nystagmus. It is concluded that urea does not, like glycerol, cause an ageotropic direction changing positional nystagmus and allows for a more accurate evaluation of vestibular function following osmolar diuresis than glycerol does.