Rebound nystagmus, a window into the oculomotor integrator.

Rebound nystagmus, a common cerebellar sign, is a transient nystagmus that appears on returning to straight-ahead gaze after prolonged eccentric gaze. The slow phases of rebound nystagmus are in the direction of prior eccentric gaze. After eccentric gaze, healthy subjects also show rebound nystagmus when fixation is removed. Rebound nystagmus is thought to be related to the function of the oculomotor neural integrator-the circuit that ensures accurate gaze holding after any eye movement-but the exact mechanism of rebound nystagmus is unknown. Here, we combine experimental data with mathematical modeling to test several hypotheses for the generation of rebound nystagmus. We show that two mechanisms contribute, one relies on vision and the other does not. Future experiments must determine if (1) the non-visual mechanism is related to eye position or to eye velocity signals and (2) whether these signals are based on afferent (proprioception) or efferent (corollary) information.

Neuro-ophthalmology of subacute sclerosing panencephalitis: two cases and a review of the literature.

PURPOSE OF REVIEW: To review the literature on early visual manifestations of subacute sclerosing panencephalitis (SSPE) with regard to two patients who had visual problems preceding the onset of neurological symptoms. One patient had cortical visual disturbances and the other had visual loss due to retinal pigment epithelial changes. RECENT FINDINGS: SSPE is a chronic encephalitis characterized by a history of measles infection and a progressive disease of the central nervous system that still occurs frequently in countries with insufficient measles immunization. Visual manifestations can occur as a result of involvement of the pathways that lead from the retina to the occipital cortex during the course of the disease, but are rare as a presenting sign. Fundus changes, especially macular retinitis and macular pigment disturbances, appear to be the most common ocular manifestations of SSPE. SUMMARY: Ophthalmologists must be aware that SSPE can knock their door with ocular findings of SSPE, months or years before the onset of neurological symptoms.