[Characteristics of Dix-Hallpike test induced nystagmus]

Objective:To retrospectively analyze the characteristics of 100 cases with Dix-Hallpike test induced nystagmus, especially the vertical downward component.Method:One hundred cases with positive Dix-Hallpike test between December 2017 and January 2018 were included in this study. Dix-Hallpike test and roll test were performed in all patients, and the max slow phase velocity (SPV), latency and duration of positional nystagmus were analyzed with SPSS 22.0 software.Result:According to the difference in the direction and duration of the nystagmus in the head-hanging position on Dix-Hallpike test, 100 patients were classified into 9 types. When only the vertical components were considered, 56 cases presented with bilateral or unilateral vertical upward component, among which 52 cases had unilateral torsional with vertical upward component, 4 cases had bilateral torsional with vertical upward component; 7 cases presented with vertically upward in one side and the vertically downward in the other side; 47 cases presented with bilateral or unilateral vertical downward component. In addition, 8 cases showed the reverse phase nystagmus. Of the 100 patients with positive Dix-hallpike, 20 cases were positive in roll test and 5 cases showing horizontal nystagmus and 15 cases showing torsional and vertical nystagmus.Conclusion:Vertical component in the positional nystagmus was common, and care should be taken to interpret the nystagmus into the underlying disorder.