The HSN test is a simple examination that can be easily performed by clinicians, however only a few studies have analyzed the 2-dimensional characteristics of HSN in patients with MD. The objective of the study was to characterize different types of 2-dimensional head-shaking nystagmus (HSN) in patients with Meniere's disease (MD). Sixty-five patients with definite MD were enrolled. HSN was considered pathologic, if slow-phase velocity (SPV) was 4 • /s and was classified as paretic or recovery according to the direction, and as monophasic or biphasic according to the presence of direction change. HSN was categorized as pure horizontal, mixed or pure vertical. When vertical SPV was larger than horizontal SPV, HSN was categorized as perverted. Forty-four patients (68%) had pathologic HSN and 28 patients (43%) had pathologic canal paresis. Monophasicparetic HSN was the most common and followed by biphasic-paretic HSN, monophasic-recovery HSN and biphasic-recovery HSN. Delayed-peak monophasic-paretic HSN, which was not observed in vestibular neuritis, was found in 6 patients with MD. Thirty-three patients (51%) had a vertical component, which was monophasic and downbeat in 32 (97%). Every pathologic HSN in horizontal plane had higher SPV in horizontal plane than that of vertical plane. Perverted HSN was found in 4 patients, of whom 3 had pure vertical and one had mixed type HSN. Our data showed that HSN is a sensitive detector of vestibular dysfunction. HSN showed diverse types with a new type of delayed-peak HSN. Vertical components of HSN were observed in about half, but they were negligible compared to horizontal components. Weak perverted HSN (vertical SPV 4 • /s) could be found in patients with MD.

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