Brain Advance Access originally published online on November 26, 2008
Brain 2009 132(1):103-115; doi:10.1093/brain/awn306
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Vergence deficits in patients with cerebellar lesions
1 Department of Neurology, University Hospitals Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, Germany 2 Institute of Neuroradiology, University Lübeck, D-23538 Lübeck, Germany
Correspondence to: Thurid Sander, MD, Department of Neurology, University Hospitals Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany E-mail: thurid.sander{at}neuro.uni-luebeck.de
The cerebellum is part of the cortico–ponto–cerebellar circuit for conjugate eye movements. Recent animal data suggest an additional role of the cerebellum for the control of binocular alignment and disconjugate, i.e. vergence eye movements. The latter is separated into two different components: fast vergence (to step targets) and slow vergence (to ramp and sinusoidal targets). The aim of this study was to investigate whether circumscribed cerebellar lesions affect these dynamic vergence eye movements. Disconjugate fast and slow vergence, conjugate smooth pursuit and saccades were binocularly recorded by a scleral search coil system in 20 patients with acute cerebellar lesions (all ischemic strokes except for one) and 20 age-matched healthy controls. Patients showed impairment of slow vergence while fast vergence was unaffected. Slow vergence gain to sinusoidal targets was significantly reduced, both in convergence and divergence direction. Divergence but not convergence velocity to ramp targets was reduced. Conjugate smooth pursuit eye movements to sinusoidal and to step-ramp targets were impaired. Patients had saccadic hypometria. All defects were particularly expressed in patients with vermis lesions. In contrast to recent animal data fast vergence was not impaired in any of our patient subgroups. We conclude that (i) the human cerebellum, in particular the vermis, is involved in the processing of dynamic vergence eye movements and (ii) cerebellar lesions elicit dissociable effects on fast and slow vergence.
Key Words: fast vergence; slow vergence; divergence; vermis
Abbreviations: FEF, frontal eye field; FOR, fastigial oculomotor region; IP, posterior interposed nucleus; MST, medial superior temporal area; NRTP, nucleus reticularis tegmenti pontis; SEF, supplementary eye field; SE, standard error; SPEM, smooth pursuit eye movements.
Received June 30, 2008. Revised September 22, 2008. Accepted October 21, 2008.
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