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Static Positional Nystagmus in the Healthy Vestibular System.

BACKGROUND
A repeat of the seminal 1973 study on static positional nystagmus (PN) using more accurate recording techniques.


PURPOSE
The purpose was to further characterize PN and, using current data, introduce new clinical criteria for its identification.


RESEARCH DESIGN
Static PN was recorded in ten positions with vision denied. Each position was analyzed using age, gender, presence, direction, and persistence of nystagmus while taking into account the number of beats and mean slow-phase velocity (SPV).


STUDY SAMPLE
One hundred healthy patients who were asymptomatic with no known neurological disorders were tested.


INTERVENTION
No intervention was used.


DATA COLLECTION
Analysis of variance, descriptive statistics, and confidence intervals were used to describe results.


RESULTS
Results showed 74% of normal participants had horizontal nystagmus in at least one position. Only 7% of the observed nystagmus was persistent. The average SPV was 2°/sec. The mean number of positions in which nystagmus was observed was three. Neither age nor gender influenced the occurrence of nystagmus. Forty-three percent of the participants had vertical nystagmus in at least one position; however, the SPV was 2°/sec or less.


CONCLUSIONS
The present study demonstrated that intermittent or persistent PN in four or fewer positions should not be considered pathological when the SPV is 4°/sec or less (n = 100). Observance of vertical nystagmus in one position should not be considered pathological if the SPV is 2°/sec or less. Suggested positions for positional testing should include seated-upright, supine, head right, head left, head-hanging, and the precaloric (30° supine) positions. Fixation when PN is observed is indicated.