title: Involuntary eyelid closure after STN-DBS: evidence for different pathophysiological entities.
abstract: OBJECTIVE
  Involuntary eyelid closure (IEC) may occur after deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson's disease (PD) and is often categorised as apraxia of lid opening (ALO), albeit the appropriateness of this term is under debate. To gain insight into the hitherto undefined pathophysiology of IEC after STN-DBS, we performed a comprehensive clinical and electrophysiological characterisation of lid function in a total of six PD patients.
  
  
  METHODS
  The study was carried out in six PD patients who developed IEC after STN-DBS. They underwent neurological examination and electromyography recording of activity in the orbicularis oculi muscle (OO) upon varying stimulation patterns. Intraoperative studies were performed in one patient.
  
  
  RESULTS
  Increasing STN-DBS intensity induced IEC in four patients, whereas it improved the condition in two. Needle EMG showed tonic hyperactivity of the OO in STN-DBS induced IEC, while variable patterns of OO activity (irregular and tonic) were seen in patients with STN-DBS-relieved IEC. Intraoperative analysis in one patient showed evidence for IEC being induced by activation of corticobulbar fibres.
  
  
  CONCLUSIONS
  We identified two groups of IEC after STN-DBS based on clinical and EMG patterns: (1) STN-DBS induced IEC associated with tonic OO overactivity and (2) STN-DBS relieved IEC presenting with variable EMG patterns. Our findings provide relevant information on pathophysiology of STN-DBS related IEC and implications for its therapeutic management.
authors.affiliation: Center of Neurology, Hertie Institute for Clinical Brain Research, and German Center for Neurodegenerative Diseases (DZNE), University of Tübingen, Tübingen, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Weiss
authors.forename: Tobias
authors.initials: T
authors.lastname: Wächter
authors.forename: Sorin
authors.initials: S
authors.lastname: Breit
authors.forename: Simon N
authors.initials: SN
authors.lastname: Jacob
authors.forename: Jörn K
authors.initials: JK
authors.lastname: Pomper
authors.forename: Friedrich
authors.initials: F
authors.lastname: Asmus
authors.forename: Josep
authors.initials: J
authors.lastname: Valls-Solé
authors.forename: Christian
authors.initials: C
authors.lastname: Plewnia
authors.forename: Thomas
authors.initials: T
authors.lastname: Gasser
authors.forename: Alireza
authors.initials: A
authors.lastname: Gharabaghi
authors.forename: Rejko
authors.initials: R
authors.lastname: Krüger
mesh_terms: D000368:Aged; D046690:Deep Brain Stimulation / Q000009:adverse effects* / Q000379:methods; D004576:Electromyography / Q000379:methods; D005141:Eyelid Diseases / Q000150:complications / Q000503:physiopathology*; D005143:Eyelids / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000628:therapy*; D011712:Pyramidal Tracts / Q000503:physiopathology; D020531:Subthalamic Nucleus / Q000503:physiopathology*