To call attention to palato-ocular synchrony, a little-known manifestation of palatal tremor.

Palatal tremor due to a lesion of the dentato-rubro-olivary pathway (Guillain-Mollaret triangle) may spread to contiguous or remote muscles. When it involves the eyes it is known as oculopalatal tremor (OPT) manifesting as pendular nystagmus, typically vertical and/or torsional, causing oscillopsia. Nystagmus may be minimal or absent with eyes open and appear only under closed eyelids, a phenomenon described in 1976 by Jacobs and Bender, and called palato-ocular synchrony (Arch Neurol;33:289) . These authors observed that palato-ocular synchrony was caused by eyelid closure rather than simply the removal of vision.

Two illustrative video case reports.  

Following brainstem hemorrhage (patient 1 – midbrain; patient 2 – pons) involving the Guillain-Mollaret triangle, two patients developed hypertrophic olivary degeneration and asymptomatic palatal tremor. In patient 1, there was no nystagmus with eyes open, but under closed eyelids, vertical oscillations were readily apparent. In patient 2, there was very subtle torsional pendular nystagmus without oscillopsia, but large vertical oscillations were apparent with eyelid closure that were synchronous with PT. The mechanism of palato-ocular synchrony is unknown but may be related to the observation that palatal tremor, due to a lesion of the Guillain-Mollaret triangle, is one of the few movement disorders that persist during sleep, and this may simply reflect eyelid closure.

 A lesion, typically stroke, involving the Guillain-Mollaret triangle often leads to delayed development of palatal tremor. Such patients should undergo a careful ocular motor examination looking for oculopalatal tremor; if absent, then the globes should be observed during active eye closure. A visible or palpable ocular oscillation under closed eyelids is known as palato-ocular synchrony, an underappreciated phenomenon that extends the spectrum of manifestations of palatal tremor.