title: Insights into gait disorders: walking variability using phase plot analysis, Huntington's disease.
abstract: Huntington's disease (HD) is a progressive inherited neurodegenerative disorder. Identifying sensitive methodologies to quantitatively measure early motor changes have been difficult to develop. This exploratory observational study investigated gait variability and symmetry in HD using phase plot analysis. We measured the walking of 22 controls and 35 HD gene carriers (7 premanifest (PreHD)), 16 early/mid (HD1) and 12 late stage (HD2) in Oxford and Cardiff, UK. The unified Huntington's disease rating scale-total motor scores (UHDRS-TMS) and disease burden scores (DBS) were used to quantify disease severity. Data was collected during a clinical walk test (8.8 or 10 m) using an inertial measurement unit attached to the trunk. The 6 middle strides were used to calculate gait variability determined by spatiotemporal parameters (co-efficient of variation (CoV)) and phase plot analysis. Phase plots considered the variability in consecutive wave forms from vertical movement and were quantified by SDA (spatiotemporal variability), SDB (temporal variability), ratio ∀ (ratio SDA:SDB) and Δangleβ (symmetry). Step time CoV was greater in manifest HD (p<0.01, both manifest groups) than controls, as was stride length CoV for HD2 (p<0.01). No differences were found in spatiotemporal variability between PreHD and controls (p>0.05). Phase plot analysis identified differences between manifest HD and controls for SDB, Ratio ∀ and Δangle (all p<0.01, both manifest groups). Furthermore Ratio ∀ was smaller in PreHD compared with controls (p<0.01). Ratio ∀ also produced the strongest correlation with UHDRS-TMS (r=-0.61, p<0.01) and was correlated with DBS (r=-0.42, p=0.02). Phase plot analysis may be a sensitive method of detecting gait changes in HD and can be performed quickly during clinical walking tests.
authors.affiliation: Movement Science Group, Oxford Brookes University, Oxford, UK. Electronic address: jcollett@brookes.ac.uk.
authors.forename: Johnny
authors.initials: J
authors.lastname: Collett
authors.affiliation: Movement Science Group, Oxford Brookes University, Oxford, UK. Electronic address: pesser@brookes.ac.uk.
authors.forename: Patrick
authors.initials: P
authors.lastname: Esser
authors.affiliation: Department of Rehabilitation Science, Jordan University of Science and Technology, Jordan. Electronic address: hwkhalil8@just.edu.jo.
authors.forename: Hanan
authors.initials: H
authors.lastname: Khalil
authors.affiliation: School of Healthcare Studies, Cardiff University, Cardiff, UK. Electronic address: BusseME@cardiff.ac.uk.
authors.forename: Monica
authors.initials: M
authors.lastname: Busse
authors.affiliation: School of Healthcare Studies, Cardiff University, Cardiff, UK. Electronic address: quinnL1@cardiff.ac.uk.
authors.forename: Lori
authors.initials: L
authors.lastname: Quinn
authors.affiliation: School of Healthcare Studies, Cardiff University, Cardiff, UK. Electronic address: DebonoK1@cardiff.ac.uk.
authors.forename: Katy
authors.initials: K
authors.lastname: DeBono
authors.affiliation: Cardiff Schools of Biosciences and Medicine, Cardiff University, Cardiff, UK. Electronic address: rosserae@cardiff.ac.uk.
authors.forename: Anne
authors.initials: A
authors.lastname: Rosser
authors.affiliation: Clinical Genetics, University of Oxford, Oxford, UK; Department of Clinical Neurology, University of Oxford,Oxford, UK. Electronic address: andrea.nemeth@eye.ox.ac.uk.
authors.forename: Andrea H
authors.initials: AH
authors.lastname: Nemeth
authors.affiliation: Movement Science Group, Oxford Brookes University, Oxford, UK; School of Healthcare Studies, Cardiff University, Cardiff, UK; Department of Clinical Neurology, University of Oxford,Oxford, UK. Electronic address: hdawes@brookes.ac.uk.
authors.forename: Helen
authors.initials: H
authors.lastname: Dawes
mesh_terms: D005260:Female; D020233:Gait Disorders, Neurologic / Q000503:physiopathology*; D006801:Humans; D006816:Huntington Disease / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D015203:Reproducibility of Results; D012720:Severity of Illness Index
keywords: Gait; Huntington's disease; Motor control; Outcome measure; Variability