title: Development and validation of the deep brain stimulation impairment scale (DBS-IS).
abstract: Bilateral deep brain stimulation of the subthalamic nucleus (STN-DBS) has considerable influence on motor and non-motor symptoms in Parkinson's disease (PD). While improvements in motor functioning can be easily assessed with general quality of life questionnaires, the measurement of specific STN-DBS-associated impairments often remains insufficient. Hence, we aimed to develop a questionnaire that measures STN-DBS-related impairments.
  
  
  
  The development of the (STN-)DBS Impairment Scale (DBS-IS) consisted of four steps. First, 30 semi-structured interviews before, three and twelve months after STN-DBS-surgery were performed to create 76 items that relate to motor and non-motor functioning in STN-DBS PD patients. Second, pilot-testing led to a rewording of the questions for better understanding. Third, a first multicentre survey was performed to reduce items by applying principal component analysis (PCA). Fourth, a second multicentre survey was conducted to examine factor structure, reliability (internal consistency) and validity.
  
  
  
  After the first survey (N = 215), the PCA lead to a reduction of 54 items. After the second survey (N = 391), exploratory factor analysis determined six factors with 22 items: 1. Postural instability and gait difficulties (5 items), 2. Cognitive impairment (5 items), 3. Speaking problems (3 items), 4. Apathy (3 items), 5. Impulsivity (3 items), and 6. Difficulties related to the DBS device (3 items). High reliability was reported for all subscales (Cronbach's alpha 0.71-0.90). Similarly, construct validity was high (r > 0.50, p < 0.001).
  
  
  
  With this new questionnaire patients can be followed-up and STN-DBS-specific problems might be adequately measured. Also, comparisons between patients with and without STN-DBS might be possible.
authors.affiliation: Department of Neurology, University of Cologne, Cologne, Germany. Electronic address: franziska.maier@uk-koeln.de.
authors.forename: Franziska
authors.initials: F
authors.lastname: Maier
authors.affiliation: Department of Neurology, University of Cologne, Cologne, Germany.
authors.forename: Catharine J
authors.initials: CJ
authors.lastname: Lewis
authors.affiliation: Department of Neurology, University of Cologne, Cologne, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Eggers
authors.affiliation: Department of Neurology, Movement Disorders Unit, Charité - University Medicine (CVK), Berlin, Germany.
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Kühn
authors.affiliation: Department of Neurology, Movement Disorders Unit, Charité - University Medicine (CVK), Berlin, Germany.
authors.forename: Henriette
authors.initials: H
authors.lastname: Krug
authors.affiliation: Department of Neurology, University of Wuerzburg, Wuerzburg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Volkmann
authors.affiliation: Department of Neurology, University of Wuerzburg, Wuerzburg, Germany.
authors.forename: Anna D
authors.initials: AD
authors.lastname: Kirsch
authors.affiliation: Department of Neurology, Movement Disorders and Neuromodulation, University Clinic Duesseldorf, Duesseldorf, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Wojtecki
authors.affiliation: Department of Neurology, Movement Disorders and Neuromodulation, University Clinic Duesseldorf, Duesseldorf, Germany.
authors.forename: Alfons
authors.initials: A
authors.lastname: Schnitzler
authors.affiliation: Department of Neurology, Christian-Albrecht-University, Kiel, Germany.
authors.forename: Günther
authors.initials: G
authors.lastname: Deuschl
authors.affiliation: Department of Neurosurgery, Medical School Hannover, Hannover, Germany.
authors.forename: Joachim K
authors.initials: JK
authors.lastname: Krauss
authors.affiliation: Research Unit Ethics, Institute for the History of Medicine and Medical Ethics, University of Cologne, Cologne, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Woopen
authors.affiliation: Department of Neurology, University of Cologne, Cologne, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Timmermann
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D046690:Deep Brain Stimulation / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000523:psychology / Q000601:surgery*; D010865:Pilot Projects; D011183:Postoperative Complications / Q000175:diagnosis* / Q000523:psychology; D011788:Quality of Life; D015203:Reproducibility of Results; D020531:Subthalamic Nucleus / Q000601:surgery; D011795:Surveys and Questionnaires / Q000592:standards*
keywords: Deep brain stimulation; Factor analysis; Parkinson's disease; Patient outcome; Quality of life