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 aetiology,
according to a study published online in Neurology.

Sun-Uk Lee, MD, 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 favourable, with a resolution or improvement of the symptoms in
more than half of the patients, with none developing VM, MD, or cerebellar
dysfunction.

“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.

Source: http://www.physiciansbriefing.com/Article.asp?AID=734211

Reference: Lee
S-U, et al. Recurrent spontaneous vertigo with interictal headshaking nystagmus.
Neurology. Published 23 May 2018.