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ABSTRACT: Turning is the most important trigger for freezing of gait (FOG). The aim of this study was to investigate the relationship between impaired head-pelvis rotation during turning and FOG. Head, trunk, and pelvic rotation were measured at onset and throughout a 180-degree turn in 13 freezers and 14 nonfreezers (OFF medication). We also studied 14 controls at preferred and slow speed to investigate the influence of turn velocity on axial rotation. Location and duration of FOG episodes were defined during the turn. At turning onset, head rotation preceded thorax and pelvic rotation in all groups, but this craniocaudal sequence disappeared when FOG occurred. Maximum head-pelvis separation was significantly greater in controls, compared to freezers and nonfreezers (35.4 versus 25.7 and 27.3 degrees; P < 0.01), but this finding was speed dependent. Timing of maximum head-pelvis separation was delayed in freezers, compared to nonfreezers and controls, irrespective of turn velocity. This delay was correlated with increased neck rigidity (R = 0.62; P = 0.02) and worsened during FOG trials. FOG occurred more often at the end of the turn, when difference in rotation velocity between head and pelvis was greatest. Even after controlling for speed and disease severity, turning in freezers was characterized by delayed head rotation and a closer coupling between head and pelvis, especially in turns where FOG occurred. These changes may be attributed to delayed preparation for the change in walking direction and, as such, contribute to FOG. © 2013 Movement Disorder Society.
Movement Disorders 02/2013; · 4.51 Impact Factor
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ABSTRACT: Objective: Freezing of gait (FOG) in Parkinson's disease (PD) may involve specific impairments in acquiring automaticity under working memory load. This study examined whether implicit sequence learning, with or without a secondary task, is impaired in patients with FOG. Method: Fourteen freezers (FRs), 14 nonfreezers (nFRs), and 14 matched healthy controls (HCs) performed a serial reaction time (SRT) task with a deterministic stimulus sequence under single-task (ST) and dual-task (DT) conditions. The increase in reaction times (RTs) for random compared with sequenced blocks was used as a measure of implicit sequence learning. Neuropsychological tests assessing global cognitive functioning and executive dysfunction were administered in order to investigate their relation to sequence learning. Results: nFRs and HCs showed significant implicit sequence learning effects (p < 0.001). FRs demonstrated a tendency to learn sequence-specific information in the SRT-ST task (p = 0.07) but not in the SRT-DT task (p = 0.69). Severity of FOG, however, correlated positively with SRT-DT task performance (r = -0.56; p < 0.05). Conclusions: The present results suggest that PD patients suffering from FOG pathology exhibit a specific impairment in the acquisition of automaticity. When working memory capacity is supplementarily loaded by adding a DT, sequence learning in FRs becomes increasingly impaired. These findings indicate that therapies should focus on extensive training in acquiring novel motor activities and reducing working memory load to improve learning in FOG. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
Neuropsychology 01/2013; 27(1):28-36. · 3.82 Impact Factor
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ABSTRACT: Freezing of gait (FOG) is part of a complex clinical picture in Parkinson's disease (PD) and is largely refractory to standard care. Diverging hypotheses exist about its origins, but a consolidated view on what determines FOG is lacking. The aim of this study was to develop an integrative model of FOG in people with PD. This cross-sectional study included 51 Parkinson subjects: 24 patients without FOG and 27 with FOG matched for age, gender, and disease severity. Subjects underwent an extensive clinical test battery evaluating general disease characteristics, gait and balance, nongait freezing, and cognitive functions. The relative contribution of these outcomes to FOG was determined using logistic regression analysis. The combination of the following four independent contributors provided the best explanatory model of FOG (R(2) = 0.49): nongait freezing; levodopa equivalent dose (LED); cognitive impairment; and falls and balance problems. The model yields a high-risk profile for FOG (P > 95%) when Parkinson patients are affected by at least one type of nongait freezing (e.g., freezing of other repetitive movements), falls or balance problems during the last 3 months, and a Scales for Outcomes in Parkinson's Disease-Cognition score below 28. A high LED further increases the risk of FOG to 99%. Nongait freezing, increased dopaminergic drug dose, cognitive deficits, and falls and balance problems are independent determinants of FOG in people with PD and may play a synergistic role in its manifestation. © 2012 Movement Disorder Society.
Movement Disorders 10/2012; · 4.51 Impact Factor
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ABSTRACT: Freezing of gait (FOG) is an incapacitating problem in Parkinson's disease that is difficult to manage therapeutically. We tested the hypothesis that impaired rhythm and amplitude control is a common mechanism of freezing which is also present during other rhythmic tasks. Therefore, we compared the occurrence and spatiotemporal profiles of freezing episodes during upper limb motion, lower limb motion, and FOG. Eleven freezers, 12 non-freezers, and 11 controls performed a rhythmic bilateral finger movement task. The triggering effect of movement speed, amplitude, and coordination pattern was evaluated. Regression slopes and spectral analysis addressed the spatial and temporal kinematic changes inherent to freezing episodes. The FOG Questionnaire score significantly predicted severity of upper limb freezing, present in 9 freezers, and of foot freezing, present in 8 freezers. Similar to gait, small-amplitude movements tended to trigger upper limb freezing, which was preceded by hastened movement and a strong amplitude breakdown. Upper limb freezing power spectra were broadband, including increased energy in the "freeze band" (3-8 Hz). Contrary to FOG, unilateral upper limb freezing was common and occurred mainly on the disease-dominant side. The findings emphasize that a core motor problem underlies freezing which can affect various movement effectors. This deficit may originate on the disease-dominant body side and interfere with amplitude and timing regulation during repetitive limb movements. These results may shift current thinking on the origins of freezing as being not exclusively a gait failure.
Movement Disorders 02/2012; 27(2):254-63. · 4.51 Impact Factor
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ABSTRACT: Freezing of gait (FOG) is a significant clinical problem in Parkinson disease (PD). Similar freezing-like episodes occur during finger movements, but little is known about ongoing motor problems during repetitive hand movements.
To investigate if the regulation of bimanual movements is impaired in those with FOG and if withdrawal of an auditory cue amplifies this problem.
A total of 23 PD patients (11 with and 12 without FOG) and 11 controls (CTRLs) performed repetitive finger movements, either externally paced or following cue withdrawal. Movement frequency, amplitude, and coordination pattern were manipulated. The stability and accuracy of movement were evaluated after exclusion of freezing trials.
With auditory pacing present, movement performance was comparable between groups. Following cue withdrawal, motor control deteriorated in those with FOG, resulting in smaller and less stable amplitudes, hastened and more variable frequency, and decreased coordination stability. Conversely, the performance of those without FOG remained mostly similar to that of CTRLs.
Compared with those without FOG, those with FOG show greater continuous dyscontrol of bimanual movements, similar to the continuous timing and scaling difficulties during locomotion. Those with FOG also benefit from auditory cueing during upper-limb movements, but these are highly cue dependent. This implies that internal timekeeping functions are more disturbed in those with FOG, who may require rehabilitation strategies for repetitive upper-extremity tasks that include cueing and imagery.
Neurorehabilitation and neural repair 01/2012; 26(6):636-45. · 4.49 Impact Factor
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ABSTRACT: Freezing of gait (FOG) in Parkinson disease (PD) may involve executive dysfunction. This study examined whether executive functioning and attention are more affected in patients with FOG compared with those without and determined whether these processes are influenced by anti-Parkinson medication.
A total of 11 PD patients with FOG, 11 without FOG, and 10 healthy control subjects, matched for age, gender, and education, participated. General motor, mental and cognitive screening tests, as well as specific neuropsychological assessment of executive functions and the Attention Network Test (ANT) were administered. The ANT was conducted in both ON and OFF phases in a counterbalanced design to determine medication-specific effects.
FOG showed a clear association with impairment in the executive control network for conflict resolution (inhibition of unwanted responses and impaired response selection), compared with nonfreezers and healthy controls, F(2, 28) = 5.41, P = .01. Orienting and alerting function did not differ between groups, F < 1. Other executive functions, such as abstract problem solving and mental flexibility were not associated with FOG (P > .10). Anti-Parkinson medication did not ameliorate conflict resolution (P > .10), although orienting attention improved with medication, F(1, 17) = 9.81, P < .01.
This study shows an association between impaired conflict resolution and FOG, important in understanding the interplay between cognitive and motor problems, which can lead to specific rehabilitation strategies.
Neurorehabilitation and neural repair 04/2011; 25(8):765-73. · 4.49 Impact Factor
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ABSTRACT: Turning is the most important trigger for freezing of gait (FOG) in Parkinson's disease (PD), and dual-tasking has been suggested to influence FOG as well.
To understand the effects of dual tasking and turning on FOG. Methods: 14 Freezers and 14 non-freezers matched for disease severity and 14 age-matched controls were asked to turn 180° and 360° with and without a cognitive dual-task during the off-period of the medication cycle. Total number of steps, duration, cadence, freezing-frequency, and secondary-task performance were measured.
Seven freezers froze during the protocol. Freezing occurred in 37.5% of trials during 180° turning compared to 0% during straight-line walking (X(2) = 10.44, p < 0.01). The occurrence of FOG increased during 360° when also a dual-task was added (X(2) = 4.23, p = 0.04). Freezers took significantly more steps and were slower than controls in all conditions. The presence of a dual-task increased these differences. Cadence increased significantly for freezers during 360° and 180° compared to straight-line walking. In contrast, cadence was decreased during turning in controls and non-freezers. During straight-line walking, only freezers made errors in the secondary task. Controls increased their error-rate during 180° turning, whereas freezers deteriorated their secondary task performance during 360°.
360° turning in combination with a dual-task is the most important trigger for freezing. During turning, non-freezers and controls decreased their cadence whereas freezers increased it, which may be related to FOG. Freezers adopted a posture second strategy in contrast to non-freezers when confronted with a dual task.
Movement Disorders 11/2010; 25(15):2563-70. · 4.51 Impact Factor
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ABSTRACT: Turning has been associated with instability, falls, and freezing in people with Parkinson's disease (PD).
To investigate the effect of different modalities of rhythmic cueing on the duration of a functional turn in freezers and nonfreezers.
A total of 133 patients with idiopathic PD while in the on phase of the medication cycle participated in this study as part of a subanalysis from the RESCUE trial. The effect of 3 different cue modalities on functional turning performance was investigated, involving a 180 degrees turn while picking up a tray. Time to perform this task was measured using an activity monitor. Tests were performed without cues and with auditory, visual, and somatosensory cues delivered in a randomized order at preferred straight-line stepping frequency.
Cueing (all types) increased the speed of the turn in all subjects. There was no difference between turn performance of freezers and nonfreezers in cued and noncued conditions. Auditory cues made turning significantly faster than visual cues (P < .01) but not compared with somatosensory cues, except in nonfreezers. There was a short-term carryover in the final noncued trial.
Rhythmical cueing yielded faster performance of a functional turn in both freezers and nonfreezers. This may be explained by enhancing attentional mechanisms during turning. Although no harmful effects were recorded, the safety of cueing for turning as a therapeutic strategy needs further study.
Neurorehabilitation and neural repair 06/2009; 23(8):831-6. · 4.49 Impact Factor
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ABSTRACT: Freezing of gait (FOG) in patients with Parkinson's disease (PD) is a common problem of unknown origin, which possibly reflects a general motor control deficit. We investigated the relationship between the frequency of freezing episodes during gait and during a bimanual task in control and subjects with PD with and without FOG. Group differences in spatiotemporal characteristics were also examined as well as the effects of visual cueing. Twenty patients with PD in the off-phase of the medication cycle and five age-matched controls performed a repetitive drawing task in an anti-phase pattern on a digitizer tablet. The task was offered at two different speeds (comfortable and maximal) and two different amplitudes (small and large) with and without visual cueing. The results showed that freezing episodes in the upper limbs occurred in only 10.4% of patient trials and that their occurrence was correlated with FOG scores (Spearman's rho = 0.64). Overall, few spatiotemporal differences were found between freezers, non-freezers and controls, except for an overshooting of the target amplitude in controls. Effects of visual cueing were largely similar in all groups, except for the variability of relative phase, which decreased in non-freezers and controls, and was unaffected in freezers. Despite the fact that general motor differences between subgroups were small, freezing episodes were manifest during a bimanual repetitive upper limb task and were correlated to FOG. Further study into upper limb movement breakdown is warranted to understand the parallel deficits that lead up to FOG.
European Journal of Neuroscience 05/2009; 29(7):1422-30. · 3.63 Impact Factor
