title: The clinical significance of freezing while turning in Parkinson's disease.
abstract: Freezing of gait (FoG) in people with Parkinson's disease (PD) is an environmentally sensitive, intermittent problem that occurs most often during turning. FoG is difficult for clinicians to evaluate and treat because it can be difficult to elicit during a clinical visit. Here, we aimed to develop a clinically valid objective measure of freezing severity during a 2-min 360-degree turning-in-place. Twenty-eight subjects with PD (16 freezers, FoG+, and 12 nonfreezers, FoG-) in the "off" state and 14 healthy control subjects were tested. Subjects wore three inertial sensors (one on each shin and one on the waist) while (1) turning in place for 2 min (alternating 360 degrees to the right with 360 degrees to the left) and (2) performing an Instrumented 7-m Timed Up and Go test (ITUG). Performance was videotaped, and clinical severity of FoG was independently rated by two movement disorders specialists (co-authors). Turning in place consistently resulted in FoG (13 out of 16 subjects with PD) while FoG was clinically observed in only two subjects with PD during the ITUG test. The Freezing Ratio during the turning test was significantly correlated with the clinical ratings (ρ=0.7, p=0.003) and with score on the new FoG questionnaire (ρ=0.5, p=0.03). After correcting for symptom severity (UPDRS-III), out of the four objective measures of the turning test (total number of turns, average turn peak speed and average turn smoothness), only the Freezing Ratio was significantly different across groups (p=0.04). Freezing can be well quantified with body-worn inertial sensors during a 2-min turning-in-place protocol.
authors.affiliation: Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97209, USA. Electronic address: mancinim@ohsu.edu.
authors.forename: Martina
authors.initials: M
authors.lastname: Mancini
authors.affiliation: Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97209, USA.
authors.forename: Katrijn
authors.initials: K
authors.lastname: Smulders
authors.affiliation: Department of Psychology & Communication Studies, University of Idaho, 875 Perimeter Drive MS3043, Moscow, ID 83844, USA.
authors.forename: Rajal G
authors.initials: RG
authors.lastname: Cohen
authors.affiliation: Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97209, USA; Medical Veterans Affairs Portland Health Care System (VAPORHCS), 3710 SW US Veterans Hospital Road, Portland, OR 97239, USA.
authors.forename: Fay B
authors.initials: FB
authors.lastname: Horak
authors.affiliation: Neurological Institute Tel Aviv Medical Center, Sackler School of Medicine, Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Nir
authors.initials: N
authors.lastname: Giladi
authors.affiliation: Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97209, USA.
authors.forename: John G
authors.initials: JG
authors.lastname: Nutt
mesh_terms: D000054:Acceleration; D000368:Aged; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D055615:Electrical Equipment and Supplies; D006801:Humans; D007866:Leg / Q000503:physiopathology; D009043:Motor Activity / Q000502:physiology; D015588:Observer Variation; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology*; D057566:Self Report; D012720:Severity of Illness Index; D060726:Torso / Q000503:physiopathology; D014741:Video Recording
keywords: freezing of gait; inertial measurement unit; turning in place