title: Freezer or non-freezer: clinical assessment of freezing of gait.
abstract: BACKGROUND
  Freezing of gait (FOG) is both common and debilitating in patients with Parkinson's disease (PD). Future pathophysiology studies will depend critically upon adequate classification of patients as being either 'freezers' or 'non-freezers'. This classification should be based ideally upon objective confirmation by an experienced observer during clinical assessment. Given the known difficulties to elicit FOG when examining patients, we aimed to investigate which simple clinical test would be the most sensitive to provoke FOG objectively.
  
  
  METHODS
  We examined 50 patients with PD, including 32 off-state freezers (defined as experiencing subjective 'gluing of the feet to the floor'). Assessment including a FOG trajectory (three trials: normal speed, fast speed, and with dual tasking) and several turning variants (180° vs. 360° turns; leftward vs. rightward turns; wide vs. narrow turning; and slow vs. fast turns).
  
  
  RESULTS
  Sensitivity of the entire assessment to provoke FOG in subjective freezers was 0.74, specificity was 0.94. The most effective test to provoke FOG was rapid 360° turns in both directions and, if negative, combined with a gait trajectory with dual tasking. Repeated testing improved the diagnostic yield. The least informative tests included wide turns, 180° turns or normal speed full turns. Sensitivity to provoke objective FOG in subjective freezers was 0.65 for the rapid full turns in both directions and 0.63 for the FOG trajectory.
  
  
  CONCLUSIONS
  The most efficient way to objectively ascertain FOG is asking patients to repeatedly make rapid 360° narrow turns from standstill, on the spot and in both directions.
authors.affiliation: Radboud University Nijmegen Medical Centre, Donders Institute for Brain, Cognition and Behavior, Department of Neurology, The Netherlands.
authors.forename: Anke H
authors.initials: AH
authors.lastname: Snijders
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Haaxma
authors.forename: Yolien J
authors.initials: YJ
authors.lastname: Hagen
authors.forename: Marten
authors.initials: M
authors.lastname: Munneke
authors.forename: Bastiaan R
authors.initials: BR
authors.lastname: Bloem
mesh_terms: D005260:Female; D005684:Gait / Q000502:physiology; D020233:Gait Disorders, Neurologic / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology; D010808:Physical Examination / Q000379:methods / Q000592:standards*; D011795:Surveys and Questionnaires