Light cupula of the horizontal semicircular canal occurring alternately on both sides: a case report.

Background: The light cupula is a condition wherein the cupula of the semicircular canal has a lower specific gravity than its surrounding endolymph. It is characterized by a persistent geotropic direction-changing positional nystagmus in the supine head-roll test, and the identification of a null plane with slight head-turning to either side.

Case presentation: This study describes a case of recurring light cupula that occurred alternately on both sides. At the first episode, a null plane was identified on the right side, which led to the diagnosis of a light cupula on the right side. At the second episode, a null plane was identified on the left side, leading to the diagnosis of a light cupula on the left side.

Conclusion: This is the first case report of recurring light cupula alternately involving both sides. Although the pathophysiology is not entirely understood yet, the light cupula should be considered as one of causes of recurrent positional vertigo.