The introduction of a headshake protocol within a bedside examination or VNG is often useful in revealing an active or yet uncompensated vestibulopathy within the frequency of the VOR. The protocol is performed with the patient seated, however its sensitivity will be enhanced when performed in a lateral body position. The caveat is that the patient must be in a vision-denied condition to ensure absence of a visual suppression effect, requiring VOG or VNG video-goggle. Frenzels will not provide this, as the patient can easily see the insides of the goggle.
As can be seen in this video case study, the post head shake nystagmus beats away (slow phase) from the impaired end-organ with the fast phase towards the intact labyrinth (Ewald’s 2nd Law). This is the most common pattern, but a recovery nystagmus may show a reversal of this pattern. Numerous investigators have reported a sensitivity of as high as 95%, but with somewhat poor specificity (49%).
The presence of the nystagmus is a clear indication that the patient is an uncompensated state and an ideal candidate for Vestibular Rehabilitation. This may be further correlated with other function tests such as CTSIB, Dynamic Visual Acuity, etc.