Mastication-induced vertigo and nystagmus.

Even though trigeminovestibular connections are well established in animals,
mastication-induced dizziness has been described only as a vascular steal
phenomenon in humans. We determined induction or modulation of nystagmus in two
index patients with mastication-induced vertigo, 12 normal controls, and 52
additional patients with peripheral (n = 38, 26 with vestibular
neuritis/labyrinthitis and 12 with Meniere's disease) or central (n = 14, 11 with
Wallenberg syndrome, two with cerebellar infarction, and one with pontine
infarction) vestibulopathy during their acute or compensated phase. Both index
patients developed mastication-induced vertigo after near complete resolution of
the spontaneous vertigo from presumed acute unilateral peripheral vestibulopathy.
The nystagmus and vertigo gradually built up during mastication and dissipated
slowly after cessation of mastication. Brain MRI and cerebral angiography were
normal in these patients. Mastication did not induce nystagmus in normal
controls. However, mastication induced nystagmus in five (24 %) of the 21
patients without spontaneous nystagmus (SN) but with a previous history of a
vestibular syndrome, and either increased (21/31, 68 %) or decreased (7/31, 23 %)
the SN in almost all the patients (28/31, 90 %) with SN. Mastication may induce
significant vertigo and nystagmus in patients with a prior history of acute
vestibulopathy. The induction or modulation of nystagmus by mastication in both
peripheral and central vestibulopathies supports trigeminal modulation of the
vestibular system in human. The gradual build-up and dissipation suggest a role
of the velocity storage mechanism in the generation of mastication-induced
vertigo and nystagmus.