Perverted head-shaking nystagmus: A possible mechanism

The authors describe a patient with acute MS who developed vertigo (tumblin g) and downbeat nystagmus upon horizontal head oscillation (perverted head- shaking nystagmus). The only abnormality on brain MRI was a hyperintense si gnal in the caudal medulla that contains the nucleus Roller and nucleus int ercalatus. These nuclei project to structures involved in the velocity stor age system for horizontal vestibulocular reflex (VOR) and vertical VOR, and also to the vestibular cerebellum. The authors offer possible mechanisms f or perverted nystagmus in this patient.