Caloric vs VHIT for the Meniere’s Patient
Due to the introduction of the vHIT in the traditional vestibular clinic, one question continues to arise. Why do the caloric results and the vHIT results not always agree in patients’ with Meniere’s disease?Drs McGarvie, Curthoys, MacDougall and Halmagyi delved into the human and animal vestibular research in search of an answer.
“In patients’ with Meniere’s disease (MD), caloric testing can show, depending on the stage and activity of the disease, a variety of results. In between attacks, many, or perhaps even most, patients with unilateral early or mild MD have normal caloric tests; late MD can show abnormalities ranging from mild to severe unilateral canal paresis without or with directional preponderance. The explanation of canal paresis in MD is not clear. The most obvious explanation, severe loss of lateral canal hair cells, is not likely to be correct because hair cell loss will not explain the fluctuating canal paresis to caloric stimulation. In contrast, the published evidence is that rotational testing of semicircular canal function in MD patients typically shows little reduction in function and even enhancement of vestibulo-ocular reflex gain, at least in the early stages of the disease. Here we offer a novel explanation for this dissociation. We propose that hydropic expansion of the lateral canal membranous labyrinth permits convective recirculation within the duct that allows dissipation of the hydrostatic force that would normally cause cupular displacement and nystagmus in the caloric test.” Access publication