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Eyelid Movements During Blinking in Patients With Parkinson’s Disease Marko Koros ˇec, MD, MSc, 1 * Ignac Zidar, BSc, 1 Dik Reits, PhD, 2 Craig Evinger, PhD, 3 and Frans VanderWerf, PhD 2 1 Institute of Clinical Neurophysiology, Division of Neurology, University Medical Center, Ljubljana, Slovenia; 2 Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands; 3 Departments of Neurobiology & Behavior and Ophthalmology, State University of New York Stony Brook, Stony Brook, New York, USA Abstract: We examined eyelid movements during spontane- ous, voluntary, and trigeminal reflex blinks in 16 patients with mild to moderate Parkinson’s disease (PD) off medi- cation and 14 controls. Voluntary and reflex blink ampli- tudes tended to be smaller than normal for PD patients, whereas eyelid kinematics (amplitude–maximum velocity relationship) for all three blink types were normal. Spon- taneous blink rate was less than normal for 10 patients and abnormally high for 6 patients. A significant positive cor- relation between spontaneous blink amplitude and blink rate was found. These observations suggest that PD modi- fies the gain of a premotor blink circuit shared by sponta- neous, voluntary, and reflex blinks. © 2006 Movement Dis- order Society Key words: Parkinson’s disease; eyelid movements; blink kinematics; blink rate Spontaneous and voluntary limb movements of pa- tients with Parkinson’s disease (PD) typically are of low velocity (bradykinesia) and reduced amplitude (hypoki- nesia). 1 Consistent with limb movement deficits in PD, some studies indicate that the spontaneous blinks of patients with advanced PD are smaller than those of controls. 2 Nevertheless, unlike limb movements, the pat- tern of muscle activity that generates blinks is stereo- typed and movement direction is constant. An antago- nistic interaction between the lid closing orbicularis oculi (OO) and the lid opening levator palpebrae superioris (LPS) muscles results in a rapid down motion of upper eyelid, followed by a slower return to the open position. This finding is true for all types of blinks: spontaneous, voluntary, or reflex. 3,4 Like saccadic eye movements, all blinks exhibit a positive linear relationship between am- plitude and maximum velocity, blink kinematics. 3,4 It is possible that PD affects the amplitude of blinks without changing their kinematics. A low velocity, small ampli- tude blink does not necessarily indicate abnormal move- ment kinematics as it does with limb movements. Thus, it is essential to measure the eyelid movements for dif- ferent types of blinks in PD quantitatively. The purpose of this study was to test whether mild to moderately motor-impaired PD patients had hypokinetic eyelid movements during spontaneous and voluntary blinks, which achieved appropriate maximum velocities, i.e., had normal blink kinematics. Despite the reduced inhibition of the trigeminal blink system caused by PD, 5,6 reflex blinks should be hypokinetic but also exhibit nor- mal kinematics. Finally, we predicted that mild to mod- erate PD modified spontaneous blink rate as occurs with more severe PD. SUBJECTS AND METHODS Sixteen patients with idiopathic PD were recruited consecutively from the outpatient movement disorder clinic at University Medical Center Ljubljana (Table 1). Patients were studied after overnight withdrawal of antiparkinsonian medication. The motor disability of patients off medication was evaluated using the Uni- fied Parkinson’s Disease Rating Scale (UPDRS) motor subsection score. Although disease duration ranged between 0.8 and 15 years, all the patients were in the Hoehn & Yahr stage 2.5 or 3. No patients exhibited any signs of blepharospasm, and none complained of dry eye symptoms. 7 Fourteen age-matched healthy subjects with no history of neurological disease nor receiving medication known to affect blinking served as controls. The national research ethics committee approved the study. Movements of both upper eyelids were measured with the magnetic search coil technique 8 (for detailed infor- *Correspondence to: Dr. Marko Koros ˇec, Institute of Clinical Neu- rophysiology, Division of Neurology, University Medical Center, Za- los ˇka 7, SI-1525 Ljubljana, Slovenia. E-mail: marko.korosec@kclj.si Received 28 June 2005; Revised 16 December 2005; Accepted 23 December 2005 Published online 9 May 2006 in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/mds.20930 1248 M. KOROS ˇ EC ET AL. Movement Disorders, Vol. 21, No. 8, 2006