HealthDay News — A hyperactive and asymmetric velocity-storage mechanism may be responsible for intermittent attacks of vertigo in some patients with recurrent spontaneous vertigo (RSV) of unknown etiology, according to a study published online May 23 in Neurology.

Sun-Uk Lee, M.D., from the Seoul National University College of Medicine in South Korea, and colleagues compared headshaking nystagmus (HSN) in 35 patients with RSV-HSN to that recorded in randomly selected patients with compensated vestibular neuritis (VN), vestibular migraine (VM), and Ménière disease (MD).

The researchers found that the estimated time constant of the primary phase of HSN was 12 seconds in patients with RSV-HSN, which was longer than those in patients with VN (5 seconds), VM (5 seconds), or MD (6 seconds). Seven of the 35 patients with RSV-HSN showed vigorous long-lasting HSN with a peak slow-phase velocity >50.0 degrees/second. In five of these seven patients, HSN could have been induced even with head shaking for only 2 to 5 seconds. Over a median follow-up of 12 years from symptom onset, long-term prognosis was favorable, with a resolution or improvement of the symptoms in more than half of the patients, with none developing VM, MD, or cerebellar dysfunction.

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“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,” the authors write.

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