title: Impaired perception of surface tilt in progressive supranuclear palsy.
abstract: BACKGROUND
  Progressive supranuclear palsy (PSP) is characterized by early postural instability and backward falls. The mechanisms underlying backward postural instability in PSP are not understood. The aim of this study was to test the hypothesis that postural instability in PSP is a result of dysfunction in the perception of postural verticality.
  
  
  METHODS
  We gathered posturography data on 12 subjects with PSP to compare with 12 subjects with idiopathic Parkinson's Disease (PD) and 12 healthy subjects. Objective tests of postural impairment included: dynamic sensory perception tests of gravity and of surface oscillations, postural responses to surface perturbations, the sensory organization test of postural sway under altered sensory conditions and limits of stability in stance.
  
  
  RESULTS
  Perception of toes up (but not toes down) surface tilt was reduced in subjects with PSP compared to both control subjects (p≤0.001 standing, p≤0.007 seated) and subjects with PD (p≤0.03 standing, p≤0.04 seated). Subjects with PSP, PD and normal controls accurately perceived the direction of gravity when standing on a tilting surface. Unlike PD and control subjects, subjects with PSP exerted less postural corrective torque in response to toes up surface tilts.
  
  
  CONCLUSIONS
  Difficulty perceiving backward tilt of the surface or body may account for backward falls and postural impairments in patients with PSP. These observations suggest that abnormal central integration of sensory inputs for perception of body and surface orientation contributes to the pathophysiology of postural instability in PSP.
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, Oregon, United States of America.|Parkinson's Disease Research, Education and Clinical Center, P3-PADRECC, Veterans Affairs Portland Healthcare System (VAPORHCS), Portland, Oregon, United States of America.
authors.forename: Marian L
authors.initials: ML
authors.lastname: Dale
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, Oregon, United States of America.|Parkinson's Disease Research, Education and Clinical Center, P3-PADRECC, Veterans Affairs Portland Healthcare System (VAPORHCS), Portland, Oregon, United States of America.
authors.forename: Fay B
authors.initials: FB
authors.lastname: Horak
authors.affiliation: Departments of Physical Therapy and Bioengineering, Temple University, Philadelphia, Pennsylvania, United States of America.
authors.forename: W Geoffrey
authors.initials: WG
authors.lastname: Wright
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, Oregon, United States of America.
authors.forename: Bernadette M
authors.initials: BM
authors.lastname: Schoneburg
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, Oregon, United States of America.
authors.forename: John G
authors.initials: JG
authors.lastname: Nutt
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, Oregon, United States of America.
authors.forename: Martina
authors.initials: M
authors.lastname: Mancini
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006112:Gravitation; D018475:Head-Down Tilt; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation; D010300:Parkinson Disease / Q000503:physiopathology / Q000523:psychology; D013028:Space Perception; D013494:Supranuclear Palsy, Progressive / Q000503:physiopathology* / Q000523:psychology*