Central nystagmus in progressive supranuclear palsy: A neglected clinical feature?

Background: Progressive supranuclear palsy (PSP) features parkinsonism characterized by early postural insta-bility, falls and prominent eye movement abnormalities that consist of saccadic slowing, followed by gaze limitation. Nystagmus is not considered typical for PSP, being more commonly associated with multiple system atrophy. Objectives: To describe the prevalence and phenomenology of nystagmus in patients with PSP. Methods: 42 patients with probable PSP underwent detailed clinical eye movement examination. Patients with nystagmus performed video-nystagmography. T-test, Chi-Square test and Wilcoxon signed-rank test were used to test differences in demographic data, disease duration and PSP subtype between patients with and without nystagmus, and for analysis of video-nystagmographic data. Results: Among 42 patients with PSP, we identified 15 patients (35,7%) with gaze-evoked nystagmus, predom-inantly horizontal. Clinically, 10/15 patients had symmetrical or asymmetrical gaze -evoked nystagmus (Type 1), while 5/15 patients had dissociated gaze-evoked nystagmus related to internuclear ophthalmoplegia (Type 2). Nystagmus and eye movement abnormalities were further characterized by video-nystagmography. There was no significant difference in age, disease duration or PSP subtypes between patients with and without nystagmus. Conclusion: Central nystagmus is present in more than a third of patients with progressive supranuclear palsy. It may present as symmetrical or asymmetrical gaze-evoked nystagmus or as dissociated gaze-evoked nystagmus related to internuclear ophthalmoplegia and probably arises from neurodegeneration of the neural integrator. Nystagmus in PSP has been a hitherto under-described feature and its presence should not deter clinicians from a diagnosis of PSP.