Acute vestibular asymmetry disorder: a new disease entity in acute vestibular syndrome?

Background: Acute vestibular syndrome (AVS) is characterized by the rapid onset of vertigo, nausea, vomiting and gait unsteadiness, which lasts for days.

Aims/objectives: We report cases as acute vestibular asymmetry disorder (AVAD), with presentations that mimic vestibular neuritis (VN) but without central lesions.

Materials And Methods: We retrospectively reviewed records of patients presenting with acute spontaneous vertigo lasting more than 24 h from January 2011 to June 2016. Among 341 patients, five showed different findings that did not indicate either VN or stroke. We analyzed the clinical features and vestibular assessments of these patients.

Results: All five patients showed spontaneous nystagmus continuing for several days. However, head impulse tests (HITs) did not reveal a corrective saccade. Brain magnetic resonance imaging showed no abnormal lesions. The bithermal caloric test revealed directional preponderance without canal paresis. Finally, the slow harmonic test of the rotatory chair revealed unilateral high gain and phase within the normal range, but a significantly asymmetric response was observed. No patients showed recurrence during follow-up.

Conclusions And Significance: Our study suggests that a normal HIT in AVS is not always a dangerous sign indicating an acute stroke. From our observations, we propose that AVAD would be a new disease entity within AVS.