Diagnostic value of vibration-induced nystagmus obtained by combined vibratory stimulation applied to the neck muscles and skull of 300 vertiginous patients.

On subjects with unilateral vestibular dysfunction, the application of a vibratory stimulation (100 Hz) to the two mastoids and the vertex, and to the right and left dorsal neck muscles produces a nystagmus directed towards the good ear in 85% of patients. Fixation must be suppressed by Frenzel's glasses or video nystagmoscopy. To be significant this nystagmus must appear in at least 3 of the 5 vibratory stimulated sites. On healthy subjects nystagmus is present in 6% of cases but never in those below 30 years. In subjects affected by central vertigo, nystagmus was elicited in 10% of cases and in subjects suffering from vertigo of unknown origin in 6% of cases. Vibration nystagmus which stops immediately after stimulation differs from head shaking nystagmus which is present in only 34% of unilateral vestibular dysfunctions. Vibration occasionally produces a pseudo-caloric nystagmus which persists after stimulation. We believe that vibratory stimulation is a useful test, quick and easy to perform. In conjunction with questionnaires, clinical examination, positional testing and the results of audiometry, it gives an immediate indication of a peripheral lesion when the vertigo is seen for the first time. With unilateral deafness, a positive test leads one to suspect an acoustic neuroma. Conversely if the test becomes negative after a vestibular neuritis when it was initially positive, it is a sign of recovery.