Alternatives to (Not Substitutes for) Caloric Testing

By Alan L. Desmond and Brady S. Workman

This article is a part of the March/April 2020, Volume 32, Number 2, Audiology Today issue. The standard electronystagmography/videonystagmography (ENG/VNG) exam, first described 80 years ago, has been around for about 60 years. The recording techniques have improved, but the tests are the same. Our understanding of vestibular function and methods to evaluate the vestibular ocular reflex (VOR) also have improved, but our profession still relies primarily on VNG testing to determine vestibular function. Let’s take a critical look at this standard of care.

The Test Components

The four main components of VNG testing include the following: (1) examination for gaze and spontaneous nystagmus, with and without visual fixation, (2) oculo-motor assessment (including saccade, smooth pursuit, and optokinetic tracking), (3) positional testing, and (4) caloric testing. This article focuses primarily on the role of, and alternatives to, caloric testing. But, first, let’s briefly consider the other test components.

Gaze and Spontaneous Nystagmus

The ability to view for nystagmus under infrared assisted VNG goggles is a great advantage over any other technique. Nystagmus associated with a persistent labyrinthine asymmetry typical of vestibular neuritis, labyrinthitis, or a Meniere’s episode is often not visible through direct viewing due to suppression by visual fixation. Several alternatives to suppress visual fixation have been suggested, but none are nearly as effective as placing the patient in total darkness with eyes open. Fresnel lenses have been used as a substitute, but Guidetti et al (2006) demonstrated that only about 40 percent of patients with nystagmus visible under VNG goggles had visible nystagmus with Fresnel lenses. Other techniques have been suggested, such as shining a penlight in the eye or having the patient stare at a large piece of paper, but these are not as effective at eliminating visual fixation as VNG goggles (Newman-Toker et al, 2009).