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Abnormalities of optokinetic nystagmus in progressive supranuclear palsy

¹ Department of Neurology, Case Western Reserve University, Cleveland, Ohio 44106, USA
² Department of Biomedical Engineering, Case Western Reserve University
³ Neurology Service, Department of Veterans Affairs Medical Center and University Hospitals, Case Western Reserve University
⁴ Department of Physiology & WM Keck Foundation Center for Intergrative, Neuroscience, University of California, San Francisco, California 94143, USA
⁵ City College of New York, NY 10031, USA

Correspondence to:
Correspondence to:
Dr R J Leigh
Department of Neurology, University Hospitals, 11100 Euclid Avenue, Cleveland, Ohio, 44106-5040, USA; rjl4{at}po.cwru.edu

Objectives: To measure vertical and horizontal responses to optokinetic (OK) stimulation and investigate directional abnormalities of quick phases in progressive supranuclear palsy (PSP).

Methods: Saccades and OK nystagmus were studied in six PSP patients, five with Parkinson’s disease (PD), and 10 controls. The OK stimulus subtended 72° horizontally, 60° vertically, consisted of black and white stripes, and moved at 10–50°/s.

Results: All PSP patients showed slowed voluntary vertical saccades and nystagmus quick phases compared with PD or controls. Small, paired, horizontal saccadic intrusions (SWJ) were more frequent and larger in PSP during fixation. Vertical saccades were transiently faster at the time of SWJ and horizontal saccades in PSP. During vertical OK nystagmus, small quick phases were often combined with horizontal SWJ in all subjects; in PSP the vector was closer to horizontal. Vertical OK slow phase gain was reduced in PSP but, in most PD patients, was similar to normals. The average position of gaze shifted in the direction of vertical OK stimulus in PSP patients with preserved slow phase responses but impaired quick phases.

Conclusions: Vertical OK responses in PSP show impaired slow phase responses, and quick phases that are slowed and combined with SWJ to produce an oblique vector. SWJ facilitate vertical saccades and quick phases in PSP, but it is unclear whether this is an adaptive process or a result of the disease. A large OK stimulus is useful to induce responses that can be quantitatively analysed in patients with limited voluntary range of vertical gaze.

Abbreviations: A, amplitude; D, duration; FEM, fast eye movement; OK, optokinetic; OKN, optokinetic nystagmus; PD, Parkinson’s disease; PSP, progressive supranuclear palsy; PPRF, paramedian pontine reticular formation; PV, peak velocity; riMLF, interstitial nucleus of the medial longitudinal fasciculus; SWJ, square wave jerks

Keywords: parkinsonism; saccades; vertical gaze

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