Active versus passive head-shaking nystagmus.

CONCLUSIONS

We recommend performing the test for nystagmus actively, both when the response is analyzed at bedside or with videonystagmography. If no nystagmus is observed with the active test, it should then be performed passively.

OBJECTIVE

Head-shaking nystagmus (HSN) is a sign of vestibular dysfunction that is elicited after actively (patient) or passively (examiner) shaking a patient's head. The objective of this study was to analyze the frequency of HSN when the test is performed actively (aHSN) or passively (pHSN), and to determine whether any differences in the results might be due to age or disease state, or whether they reflect the results of different vestibular tests.

PATIENTS AND

METHODS

This was a prospective study conducted at a tertiary care center. The head-shaking test was carried out actively and passively on 100 patients. The caloric test, the rotatory chair tests and the measures of disability were performed on the same day and in the same setting. HSN was considered to be present when it was seen for a period longer than 5 s or if the maximum slow-phase velocity of HSN was higher than 3 degrees s(-1). Four groups were established according to the results of the two testing methods.

RESULTS

The frequency of aHSN was 47% and of pHSN was 46% when the presence of nystagmus was established as the criterion. Moreover, in patients who had experienced vestibular neuritis previously, the type of nystagmus was age-dependent. When the velocity of the nystagmus elicited was considered, the results coincided with the method of testing in 74% of the patients, while they differed in 26% of subjects; the aforementioned age dependency was no longer seen. Differences in the caloric and rotatory chair test results, as well as in disability, were observed in the groups generated on the basis of the types of nystagmus.