We describe pseudo nystagmus in a unique series of nine patients with progressive supranuclear palsy (PSP).

The eye movements were measured in 13 PSP patients with high-resolution corneal curvature tracker (Ober Consulting, Poland). The eye positions were calibrated with values corresponding to the known angular eye rotation measures. Pseudo nystagmus was identified and analyzed with customized software prepared in Matlab, Natick, MA in nine PSP patients. We simultaneously measured head oscillations with forehead mounted gyroscope.

We studied 13 PSP patients where gaze was steady in primary and eccentric eye position during clinical examination. Oculography with head mounted sensors, however, revealed spontaneous vertical jerk nystagmus with equal intensity in the primary and eccentric gaze orientation; downbeat in three and upbeat in six patients. The nystagmus remained in phase with head oscillations but its trajectory was opposite of that of head movement.

Pseudo nystagmus can be seen in PSP. Prominent vertical pseudo nystagmus in PSP reflects dystonia and dystonic tremor in the sagittal plane. Dystonia in sagittal plane, although common in PSP, may not have clinically appreciable head tremor. Latter can be noteworthy with instrumented measures. It can cause artefactual pseudo nystagmus in oculography with head mounted sensing system.