When a patient consults for vertigo, dizziness, instability, or imbalance, in addition to a complete otorhinolaryngological clinical evaluation—where history-taking is the most important part—as well as audiological studies and, if necessary, neuroradiological studies, it is essential to perform a targeted otoneurological examination to assess the health and function of the vestibular portion of the inner ear and the neural pathways that connect it to the central nervous system.
Body balance results from the integration of visual, proprioceptive, and vestibular information reaching the central nervous system, from which commands are sent to the oculomotor and general musculature to enable postural correction and spatial orientation.
What is computerized videonystagmography?
Computerized videonystagmography is a technique whose purpose is the electrical recording of involuntary eye movements (nystagmus), both spontaneous and induced, followed by computerized analysis.
Computerized videonystagmography with caloric stimulation (VNGc) is one of the most commonly used vestibular tests, as it is easy to perform and allows the study of each labyrinth individually, providing highly useful information for etiological diagnosis and follow-up of vertigo. Its purpose is to induce an endolymphatic current in the horizontal semicircular canal (HSC), which displaces the ampullary crest and thereby provokes nystagmus, recorded by electrical means.
How is videonystagmography performed?
To record nystagmus, goggles with an integrated video camera are used.
An initial recording is performed prior to stimulation to assess spontaneous nystagmus: its absence or presence, as well as its characteristics (intensity, direction, etc.), provide information that helps localize the origin of vertigo.
Subsequently, caloric vestibular tests are performed. The stimulus can be applied using water or cold and/or warm air. We prefer the use of air, as it has no side effects, even in cases of ear disease with tympanic membrane perforation or in postoperative patients.
Stimulation with warm air (at 44°C) causes a decrease in endolymph density, which rises through the horizontal semicircular canal toward the ampulla (ampullopetal current), producing horizontal nystagmus with the fast phase toward the stimulated ear.
Stimulation with cold air (at 30°C) causes an increase in endolymph density, resulting in an ampullofugal current and horizontal nystagmus with the fast phase toward the ear opposite the stimulated one.
The obtained values are reflected in the Klausse butterfly diagram, which allows a rapid assessment of the HSC responses and their pathophysiological interpretation.
In caloric tests, the following may be found:
- Vestibular hyporeflexia, due to unilateral peripheral vestibular involvement (neuritis, Ménière’s disease, neurinoma, etc.).
- Unilateral vestibular areflexia, in petrous bone fractures or after vestibular nerve neurectomy.
- Bilateral vestibular areflexia, in toxic ear diseases and central pathology.
- Vestibular hyperreflexia, generally bilateral and of central origin.
Analysis of the obtained results allows detection of pathology at the level of the oculomotor system, as well as neurological and vestibular disorders, whether peripheral or central.
These examinations must be performed by trained personnel and evaluated by a specialist, always in conjunction with the information provided by the clinical history, audiological studies, and other complementary tests.