The skull-vibration-induced nystagmus test in 10 points: our experience and a review of the literature

the aim of this article is to describe the clinical utility and technical conditions of the skull-vibration-induced-nystagmus (SViN) test, a recent modality of vestibular receptors stimulation using bone-conducted vibrations (BCV). SViN results, recorded under videonystagraphy and ob- served with videoscopy in more than 22,500 patients without visual fixation in our experience and collected in literature data, are summarized in 10 points. SVIN is induced instantaneously by 100 Hz BCV to either mastoid and shows a predominantly horizontal nystagmus with quick phases beating toward the opposite side in unilateral vestibular-loss; starts with stimulation onset and stops at stimulation offset, with no post- stimulation reversal. SViN is sustained during long stimulus durations, reproducible and beats in the same direction on each stimulated mastoid. SViN has no side effects; it is a useful, rapid, non-intrusive, robust indicator of asymmetry of vestibular function, and it contributes to indicate the side of the unilateral vestibular-loss (UVl). it shows little or no habituation and is permanent as a vestibular scar. SViN is usually beat- ing toward the lesion in unilateral superior canal dehiscence. it complements other tests for high frequencies in the vestibule multifrequency analysis. It is a global vestibular test stimulating at 100 Hz both canals and otolith receptors. Lastly, SVIN is more sensitive to reveal peripheral than central diseases. In UVL patients the lateral semicircular canal is the most contributing structure and SVIN horizontal component is well correlated with the caloric test results. SViN is a global canal-predominant vestibular response revealing instantaneously a peripheral vestibular asymmetry as a first-line vestibular Weber-test.