The Clinical Significance of Head-shaking Nystagmus in the Patients with Acute Unilateral Peripheral Vestibular Loss

ABSTRACT

BACKGROUND AND OBJECTIVES: In unilateral peripheral vestibular loss patients, head-shaking induce a bias from remaining asymmetric vestibular sensor and cause the imbalance in velocity-storage mechanisms. Head-shaking nystagmus(HSN) is the transient nystagmus induced by shaking the head in the horizontal plane, and have slow phases directed toward the side of vestibular loss. We evaluated the usefulness of the HSN in acute unilateral peripheral vestibular loss patient with reference to spontaneous nystagmus(SN), bithermal caloric test, and slow harmonic acceleration(SHA) test. MATERIALS AND METHODS: 18 patients of acute unilateral peripheral vestibular loss who had SN and symptoms of acute prolonged vertigo were analyzed retrospectively. The examiner performed passive head rotation in 30 degree anteflexed position with eyes closed and oscillated about 60 degree to each side, 2 Hz for 20 cycles, and the nystagmus was observed with Frenzel glasses immediately after head was stopped. Prevalence and direction of HSN were analyzed with SN, caloric test and SHA test during the follow up period. RESULTS: The prevalence of HSN was 89%(16/18). During follow-up period, direction of nystagmus was changed 28%(13/18) in SN, but in HSN, direction was fixed in all subjects. SN and HSN directed toward the same side in 75%(12/16) but in four cases(25%), direction could not compared because the direction of SN was changed during follow up peroid. In 69%(11/16) of subjects, HSN persisted after the disappearance of SN. In comparison of HSN with bithermal caloric test, direction of CP was highly correlated with direction of HSN(92%) than SN(64%). HSN was more prevalent(92%) than DP(67%) in caloric test and asymmetry(78%) in SHA test. CONCLUSIONS: HSN test, easily performed office maneuvers, is very useful method to identify the laterality of acute unilateral peripheral vestibular loss, especially in chronic stage.