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A case report on fixation instability in Parkinson’s disease with bilateral deep brain stimulation implants
  1. H A C Wark1,4,
  2. P C Garell3,4,
  3. A L Walker2,
  4. M A Basso1,2
  1. 1
    Department of Physiology, University of Wisconsin, Madison Medical School, Madison, Wisconsin, USA
  2. 2
    Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison Medical School, Madison, Wisconsin, USA
  3. 3
    Neurological Surgery, University of Wisconsin, Madison Medical School, Madison, Wisconsin, USA
  4. 4
    Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA
  1. Dr M A Basso, Department of Physiology, University of Wisconsin-Madison, 1300 University Ave, Room 127 SMI, Madison, WI 53706, USA; michele{at}


We report on fixation instabilities in a patient diagnosed with Parkinson’s disease (PD). This patient underwent deep brain stimulation (DBS) surgery bilaterally in the vicinity of the subthalamic nuclei (STN). Examination of the eye movements of this patient revealed marked fixation instability compared with a healthy age matched control. The eye movements occurring during fixation differed from other reports of fixation instabilities in that they interrupted fixation for only brief durations. These interruptive saccades (IS) had saccade-like amplitude velocity relationships. The frequency of these IS was higher in the patient with PD than in the healthy age matched control. Furthermore, the frequency of the IS in the patient reduced toward control with application of bilateral DBS in the vicinity of the STN. From our observations we conclude that fixation ability may be altered in PD and improved with DBS.

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  • Funding: This work was supported by NIH EY13692 (MAB), the Esther A and Joseph Klingenstein Foundation (MAB), a faculty development award from the Howard Hughes Medical Institute (PCG), a Hilldale Research Fellowship (HACW) and a Parkinson’s Disease Foundation Summer Research Fellowship (HACW).

  • Competing interests: None.

  • Ethics approval: The study was approved by the University of Wisconsin-Madison Institutional Review Board (IRB).