Liesbeth Münks

Explaining freezing of gait in Parkinson's disease: Motor and cognitive determinants

Freezing of gait (FOG) is part of a complex clinical picture in Parkinsons 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 (R2 = 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 Parkinsons 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.

Effects of deep brain stimulation of the subthalamic nucleus on freezing of gait in Parkinson's disease: a prospective controlled study

Background Freezing of gait (FOG) is a debilitating gait disorder in Parkinsons disease (PD) with partial responsiveness to dopaminergic medication. To date, notions about the effects of subthalamic deep brain stimulation (STN-DBS) on FOG remain controversial. Objectives To compare the effects of bilateral STN-DBS and continued best medical treatment (BMT) on FOG occurrence, FOG severity and clinical outcomes in PD patients at 6 and 12 months follow-up. Methods In this prospective, controlled study, 41 PD patients with at least 5 years disease duration participated. Twenty-four subjects (20 with FOG) were treated with STN-DBS and seventeen (15 with FOG) continued BMT. The primary outcome was the New Freezing of Gait Questionnaire (NFOGQ) at 6 months postsurgery. Other outcomes were the NFOGQ at 12 months and clinical outcomes (Unified Parkinsons Disease Rating Scale III (UPDRS III), timed gait, falls and quality of life) at both time points. Results STN-DBS increased the likelihood to convert from being a freezer to a non-freezer at 6 and 12 months follow-up (relative risk reduction=0.4). However, 45% of baseline freezers still experienced FOG 6 and 12 months postsurgery although with reduced severity. Three baseline non-freezers (1/2 BMT-treated, 2/4 STN-DBS-treated) developed FOG during follow-up. STN-DBS-induced benefits on FOG were mostly mediated by baseline levodopa equivalent dose, altered medication-intake and reduced motor fluctuations. Conclusions In contrast to continued BMT, STN-DBS reduced FOG occurrence and severity at 6 months postsurgery with largely sustained effects at 12 months follow-up. Longer follow-up periods are needed to test whether FOG improvements after STN-DBS persist with disease progression.

Protocol for a randomized comparison of integrated versus consecutive dual task practice in Parkinson's disease: the DUALITY trial

BackgroundMultiple tasking is an integral part of daily mobility. Patients with Parkinson’s disease have dual tasking difficulties due to their combined motor and cognitive deficits. Two contrasting physiotherapy interventions have been proposed to alleviate dual tasking difficulties: either to discourage simultaneous execution of dual tasks (consecutive training); or to practice their concurrent use (integrated training). It is currently unclear which of these training methods should be adopted to achieve safe and consolidated dual task performance in daily life. Therefore, the proposed randomized controlled trial will compare the effects of integrated versus consecutive training of dual tasking (tested by combining walking with cognitive exercises).Methods and designHundred and twenty patients with Parkinson’s disease will be recruited to participate in this multi-centered, single blind, randomized controlled trial. Patients in Hoehn & Yahr stage II-III, with or without freezing of gait, and who report dual task difficulties will be included. All patients will undergo a six-week control period without intervention after which they will be randomized to integrated or consecutive task practice. Training will consist of standardized walking and cognitive exercises delivered at home four times a week during six weeks. Treatment is guided by a physiotherapist twice a week and consists of two sessions of self-practice using an MP3 player. Blinded testers will assess patients before and after the control period, after the intervention period and after a 12-week follow-up period. The primary outcome measure is dual task gait velocity, i.e. walking combined with a novel untrained cognitive task to evaluate the consolidation of learning. Secondary outcomes include several single and dual task gait and cognitive measures, functional outcomes and a quality of life scale. Falling will be recorded as a possible adverse event using a weekly phone call for the entire study period.DiscussionThis randomized study will evaluate the effectiveness and safety of integrated versus consecutive task training in patients with Parkinson’s disease. The study will also highlight whether dual task gait training leads to robust motor learning effects, and whether these can be retained and carried-over to untrained dual tasks and functional mobility.Trial registrationClinicaltrials.gov NCT01375413.

Training dual tasks together or apart in Parkinson's disease: Results from the DUALITY trial

Background and Objectives: Many controversies surround the usefulness of dual‐task training in Parkinsons disease (PD). This study (1) compared the efficacy of two different dual‐task training programs for improving dual‐task gait and (2) assessed the possible fall risk of such training.

Dual tasking in Parkinson’s disease: should we train hazardous behavior?

Dual-task (DT) circumstances aggravate gait disorders in Parkinson’s disease (PD) and are associated with an increased risk of falling and reduced functional mobility. Clinical rehabilitation guidelines for PD consider DT interventions as potentially hazardous and recommend avoiding them in daily life. The current article challenges this notion and addresses the necessity of implementing DT training in PD. First, underlying reasons for DT interference in PD and current theoretical models are discussed. Subsequently, different training approaches to tackle DT difficulties are put forward. Finally, the effectiveness and limitations of DT training in PD are reviewed. We conclude that there is a need for DT interventions in PD and recommend randomized, power-based studies to further test their efficacy.

Test-Retest Reliability of Dual-Task Outcome Measures in People With Parkinson Disease

Background Dual-task (DT) training is gaining ground as a physical therapy intervention in people with Parkinson disease (PD). Future studies evaluating the effect of such interventions need reliable outcome measures. To date, the test-retest reliability of DT measures in patients with PD remains largely unknown. Objective The purpose of this study was to assess the reliability of DT outcome measures in patients with PD. Design A repeated-measures design was used. Methods Patients with PD (“on” medication, Mini-Mental State Examination score ≥24) performed 2 cognitive tasks (ie, backward digit span task and auditory Stroop task) and 1 functional task (ie, mobile phone task) in combination with walking. Tasks were assessed at 2 time points (same hour) with an interval of 6 weeks. Test-retest reliability was assessed for gait while performing each secondary task (DT gait) for both cognitive tasks while walking (DT cognitive) and for the functional task while walking (DT functional). Results Sixty-two patients with PD (age=39–89 years, Hoehn and Yahr stages II–III) were included in the study. Intraclass correlation coefficients (ICCs) showed excellent reliability for DT gait measures, ranging between .86 and .95 when combined with the digit span task, between .86 and .95 when combined with the auditory Stroop task, and between .72 and .90 when combined with the mobile phone task. The standard error of measurements for DT gait speed varied between 0.06 and 0.08 m/s, leading to minimal detectable changes between 0.16 and 0.22 m/s. With regard to DT cognitive measures, reaction times showed good-to-excellent reliability (digit span task: ICC=.75; auditory Stroop task: ICC=.82). Limitations The results cannot be generalized to patients with advanced disease or to other DT measures. Conclusions In people with PD, DT measures proved to be reliable for use in clinical studies and look promising for use in clinical practice to assess improvements after DT training. Large effects, however, are needed to obtain meaningful effect sizes.

Are factors related to dual-task performance in people with Parkinson's disease dependent on the type of dual task?

BACKGROUND Impaired dual-task performance significantly impacts upon functional mobility in people with Parkinsons disease (PD). The aim of this study was to identify determinants of dual-task performance in people with PD in three different dual tasks to assess their possible task-dependency. METHODS We recruited 121 home-dwelling patients with PD (mean age 65.93 years; mean disease duration 8.67 years) whom we subjected to regular walking (control condition) and to three dual-task conditions: walking combined with a backwards Digit Span task, an auditory Stroop task and a Mobile Phone task. We measured dual-task gait velocity using the GAITRite mat and dual-task reaction times and errors on the concurrent tasks as outcomes. Motor, cognitive and descriptive variables which correlated to dual-task performance (p < 0.20) were entered into a stepwise forward multiple linear regression model. RESULTS Single-task gait velocity and executive function, tested by the alternating intake test, was significantly associated with gait velocity during the Digit Span (R(2) = 0.65; p < 0.001), the Stroop (R(2) = 0.73; p < 0.001) and the Mobile Phone task (R(2) = 0.62; p < 0.001). In addition, disease severity proved correlated to gait velocity during the Stroop task. Age was a surplus determinant of gait velocity while using a mobile phone. CONCLUSION Single-task gait velocity and executive function as measured by a verbal fluency switching task were independent determinants of dual-task gait performance in people with PD. In contrast to expectation, these factors were the same across different tasks, supporting the robustness of the findings. Future study needs to determine whether these factors predict dual-task abnormalities prospectively.