Recurrent spontaneous vertigo with interictal headshaking nystagmus.

OBJECTIVE: To define a disorder characterized by recurrent spontaneous vertigo (RSV) of unknown etiology and interictal headshaking nystagmus (HSN).

METHODS: We characterized HSN in 35 patients with RSV-HSN compared to that recorded in randomly selected patients with compensated vestibular neuritis (VN), vestibular migraine (VM), and Ménière disease (MD).

RESULTS: The estimated time constant (TC) of the primary phase of HSN was 12 seconds (95% confidence interval [CI] 12-13) in patients with RSV-HSN, which was larger than those in patients with VN (5 seconds, 95% CI 4-5), VM (5 seconds, 95% CI 5-6), or MD (6 seconds, 95% CI 5-6). TCs of the horizontal vestibulo-ocular reflex were also larger during the rotatory chair test in patients with RSV-HSN. Among the 35 patients with RSV-HSN, 7 showed vigorous long-lasting HSN with a peak slow-phase velocity >50.0°/s. In 5 patients (5 of 7, 71%) with vigorous HSN, HSN could have been induced even with headshaking for only 2 to 5 seconds. Long-term prognosis was favorable, with a resolution or improvement of the symptoms in more than half of the patients during the median follow-up of 12 (range 2-58) years from symptom onset. None developed VM, MD, or cerebellar dysfunction during the follow-up.

CONCLUSION: The clinical features and characteristics of HSN in our patients indicate a hyperactive and asymmetric velocity-storage mechanism that gives rise to intermittent attacks of spontaneous vertigo probably when marginal compensation of underlying pathology is disrupted by endogenous or exogenous factors.