Vestibular effects of intravenous lidocaine used in the treatment of tinnitus.
Intravenous lidocaine is known to have an effect on the auditory system in that it is useful for suppressing tinnitus, albeit temporarily. We have used intravenously administered lidocaine as one of the treatment modalities for refractory, disturbing, tinnitus. Its effects on the vestibulo-ocular system were determined by electronystagmography performed before and immediately after injecting lidocaine: smooth pendular stimulus tracking was unaffected; spontaneous and positional nystagmus tended to be suppressed; directional preponderance was reduced or reversed; and the difference between the nystagmus responses in the two directions during the pendular rotation chair test was also reduced or reversed. These changes in the caloric and rotation tests were statistically significant. Lidocaine also appeared to have altered the balance between the two sides in the vestibulo-spinal system as indicated by the results of the stepping test during craniocorpography. The results lend support to the hypothesis that intravenous lidocaine acts at the level of the central nervous system rather than at the periphery.