Timothy C. Hain, MD Page last modified: January 9, 2017
The vibration test is a recent development in clinical vestibular assessment. It has been made possible by the wide availability of video Frenzel goggles, which are devices which allow one to observe a subjects eyes in complete darkness. Vibration over the head or neck may elicit a vigorous nystagmus, and furthermore, the nystagmus is frequently direction specific and allows you to identify the "bad ear" (it beats away).
|Device used for vibration test (cost -- about $25). This is a Sunbeam/Oster shower massager.|
A source of vibration, such as a hand-held shower massager is firmly applied to the mastoid, anterior or posterior neck of a subject. Others have used a "TheraSpa Turbo Brookstone" (White et al, 2007) You can use other vibrators instead -- it is not very critical except we advise against battery powered devices (which vary according to their charge status).
The other device that you need is a video-frenzel goggle system. In the past, simple systems produced a composite signal that could be directly observed on a TV monitor. Recently, the composite devices have largely been replaced by "firewire" devices, that require a PC. This is unfortunate. Optical Frenzel goggles just don't work for this test -- you need complete darkness.
|Method of vibration test. A shower massager is applied firmly to the lower edge of the sternocleidomastoid. The lower frequency setting is used (60 hz).|
Generally we apply vibration to the lower edge of the sternocleidomastoid as we want to avoid the carotid artery area, but the exact location is not at all critical as long as the sternocleidomastoid is located and the pressure is firm. The eyes are observed with a device such as a video-Frenzel goggle system. No light can be allowed. The subject is sitting upright, without instruction other than to look straight ahead.
|Vibration induced nystagmus. This patient has a 60% left weakness. There is a 3 deg/sec right-beating spontaneous nystagmus, which increases to about 10 deg/sec when vibration is applied to either sternocleidomastoid with a device that produces a 60 cycle pulse (a shower massager).|
A positive response is a horizontal nystagmus that beats in the same direction, for vibration on both sides of the neck. Above is shown a strong nystagmus, typical of vestibular neuritis or post-ITG. It is actually more common to have no spontaneous nystagmus at all, but a powerful nystagmus produced by vibration. This would be typical of the compensated unilateral loss.
Another example of the typical positive vibration test is shown here (movie, 7 meg). This individual has a complete unilateral vestibular loss secondary to removal of an acoustic neuroma on the right side 30 years prior. There is a strong nystagmus beating to the left, for vibration on either side. The subject cannot see because of the goggles which occlude vision. The vibration source is a conventional shower massager as shown above. This example illustrates that vibration induced nystagmus generally persists as long as the unilateral loss persists. In acoustic neuroma patients -- this means forever.
It is common for vibration to produce a nystagmus that beats to the left for vibration of the left neck, and to the right on vibration of the right neck. This is an "ipsi" versive DCVN. This response seems to be more frequent in older people, and has no association with any known disease. Perhaps it relates greater reliance on the neck in older people, as their ears degrade.
Occasionally (perhaps 1% of the iDCVN), there is a contraversive nystagmus that beats opposite to the side being vibrated. cDVCN. Again, there is no clinical correlation as yet.
This link is to a video of a weak cDCVN (courtesy of Dr. Dario Yacovino).
Occasionally there are large differences in the intensity of nystagmus between one side and the other. The clinical significance of this is unclear. We speculate that some of the asymmetry is due to technical issues (i.e. inconsistent application of the vibration), and that some of it is related to differences in neck proprioception. We think this is much more common in persons who have had neck surgery.
|Upbeating nystagmus induced by vibration on either side. This is of unknown significance, but it is quite rare, unless very strong vibration is used.|
Nystagmus that is vectored other than horizontally, is of unknown significance. Following the convention in ENG testing, this response can be called "perverted", because it goes in unconventional directions. In some cases it may be due to release from fixation suppression. This is generally upbeating, but downbeating and even torsional nystagmus is rarely encountered. In SCD, vertical nystagmus is occasionally reported (see below).
The vibration test nystagmus (as far as we know) persists forever. Well, at least as long as the vestibular weakness persists. Below is an example of a patient post-acoustic removal 1 year prior to testing (image courtesy of Dr. Dario Yacovino). Vibration nystagmus is stronger than head-shaking nystagmus. HSN usually becomes smaller in the territory between 50-100% loss, while vibration nystagmus scales more linearly with the extent of loss. (unpublished observations of the author). Of course, there is no caloric nystagmus (bottom right):
Here again is a link to vibration nystagmus in a patient whose acoustic was removed in the remote past. (movie, 7 meg). This individual has a complete unilateral vestibular loss secondary to removal of an acoustic neuroma on the right side 30 years prior. There is a strong nystagmus beating to the left, for vibration on either side. The subject cannot see because of the goggles which occlude vision. The vibration source is a conventional shower massager as shown above.
There is a suprisingly large literature documenting the utility of neck vibration in diagnosis of dizziness. There is also a large basic science literature documenting the deleterious effects of vibration on posture.
In essence, vibration of the neck is a moderately reliable method of localizing the side of a unilateral vestibular lesion. In complete darkness, vibration induces a nystagmus that resembles that seen acutely, prior to compensation. Vibration induced nystagmus persists over decades, unlike spontaneous nystagmus. Vibration testing was abnormal in generic vestibular neuritis in 91% of patients, and 94% of those patients with Ramsey-Hunt type of vestibular neuritis (Kim et al, 2015).
We have found that vibration induced nystagmus is an excellent method of determining whether or not transtympanic gentamicin treatment for Meniere's disease will stop vertigo attacks. (unpublished data of the author). Presumably this is due to unilateral vestibular damage.
Clinical uses of the vibration test that we find dubious
Vibration of the posterior neck is reported to be useful in diagnosis of SCD, but we are dubious ourselves. According to White et al (2007), it induces a downbeating nystagmus (White et al, 2007). We have not found this to be true in our SCD population. On the other hand, Dumas et al (2014) suggested that vibration of the vertex of the skull largely produces an upbeating nystagmus. Which is it -- downbeating or upbeating ? In our own practice, we don't think that vibration of the neck (SCM) induces any consistent nystagmus in SCD, and in those who have upbeating nystagmus, most have BPPV and not SCD. So -- This observation is so far not well established, and we haven't found this to be true in our own patients either. In other words, don't depend on it. The valsalva test is far more effective in diagnosing SCD at the bedside.
Vibration of the mastoid in Meniere's disease - Hong et al (2007) suggested that vibration over the mastoid was somewhat localizing, generally producing contralesional nystagmus, especially in persons with more vestibular damage. There are many problems with this study - -mastoid location (see above), and also a protocol where the side eliciting bigger VIN was used. We prefer a protocol where only VIN is accepted that goes the same direction for each sides, and also a protocol where the neck rather than the mastoid is stimulated. Still, we do agree that occasionally a wrong-way VIN is seen.
Vibration induced nystagmus is (in our opinioin) a more useful test than the "HIT" or head impulse test, as well as being safer (lacking the strong head thrusts), but oddly enough, much less research has been done on vibration. Some basic questions that we think would be of interest: