Periodic vertigo and downbeat nystagmus while supine: Dysfunction of Purkinje cells coding gravity

Cerebellar nodulus and uvula and their connections with the vestibular nuclei form the so‐called velocity‐storage circuit. Lesions involving the velocity‐storage circuit give rise to positional vertigo and nystagmus. Herein, we present a 32‐year‐old man with cerebellar nodulus and uvular hemorrhage who showed periodic vertigo and downbeat nystagmus in the supine position. To explain this unusual pattern, we adopted velocity‐storage model with a lesion on the neural connection between the gravity and inertia estimators, resulting in periodic neural impulses and a gravity bias in a specific position. This report expands the spectrum of central positional nystagmus due to dysfunction of the velocity‐storage mechanism.