Chava Peretz

Dual tasking, gait rhythmicity, and Parkinson's disease: which aspects of gait are attention demanding?

Cognitive function and the performance of a secondary, dual task may affect certain aspects of gait, but the relationships between cognitive function and gait are not well understood. To better understand the motor control of gait and the relationship between cognitive function and gait, we studied cognitive function and the effects of different types of dual tasking on the gait of patients with Parkinsons disease (PD) and controls, contrasting measures of gait automaticity and rhythmicity with other features. Patients with idiopathic PD (n = 30; mean age 71.8 year) with moderate disease severity (Hoehn and Yahr Stage 2–3) were compared to age and gender‐matched healthy controls (n = 28). Memory and executive function were also assessed. In both groups, gait speed decreased in response to dual tasking, in a parallel fashion. For the PD group only, gait variability increased compared to usual walking. Executive function was significantly worse in the PD group, while memory was not different in the two groups. Executive function measures were significantly correlated with gait variability during dual tasking, but not during usual walking. These findings demonstrate that regulation of gait variability and rhythmicity is apparently an automatic process that does not demand attention in healthy adults. In patients with PD, however, this ability becomes attention‐demanding and worsens when subjects perform secondary tasks. Moreover, the associations between executive function and gait variability suggest that a decline in executive function in PD may exacerbate the effects of dual tasking on gait, potentially increasing fall risk.

Dual-tasking effects on gait variability: the role of aging, falls, and executive function.

The objectives of the present study were to test the hypothesis that the dual‐tasking effect on gait variability is larger in healthy older adults than it is in healthy young adults; that this effect is larger in idiopathic elderly fallers than it is in healthy older adults; and that the dual‐tasking effects on gait variability are correlated with executive function (EF). Young adults and older adults who were classified as fallers and nonfallers were studied. Gait speed, swing time, and swing time variability, a marker of fall risk, were measured during usual walking and during three different dual‐tasking conditions. EF and memory were evaluated. When performing dual tasks, all three groups significantly decreased their gait speed. Dual tasking did not affect swing time variability in the young adults and in the nonfallers. Conversely, dual tasking markedly increased swing time variability in the fallers. While memory was similar in fallers and nonfallers, EF was different. The faller‐specific response to dual tasking was significantly correlated with tests of EF. These findings demonstrate that dual tasking does not affect the gait variability of elderly nonfallers or young adults. In contrast, dual tasking destabilizes the gait of idiopathic elderly fallers, an effect that appears to be mediated in part by a decline in EF.

Rhythmic auditory stimulation modulates gait variability in Parkinson's disease

Patients with Parkinsons disease (PD) walk with a shortened stride length and high stride‐to‐stride variability, a measure associated with fall risk. Rhythmic auditory stimulation (RAS) improves stride length but the effects on stride‐to‐stride variability, a marker of fall risk, are unknown. The effects of RAS on stride time variability, swing time variability and spatial‐temporal measures were examined during 100‐m walks with the RAS beat set to 100 and 110% of each subjects usual cadence in 29 patients with idiopathic PD and 26 healthy age‐matched controls. Carryover effects were also evaluated. During usual walking, variability was significantly higher (worse) in the patients with PD compared with the controls (P < 0.01). For the patients with PD, RAS at 100% improved gait speed, stride length and swing time (P < 0.02) but did not significantly affect variability. With RAS at 110%, reductions in variability were also observed (P < 0.03) and these effects persisted 2 and 15 min later. In the control subjects, the positive effects of RAS were not observed. For example, RAS increased stride time variability at 100 and 110%. These results demonstrate that RAS enables more automatic movement and reduces stride‐to‐stride variability in patients with PD. Further, these improvements are not simply a by‐product of changes in speed or stride length. After walking with RAS, there also appears to be a carryover effect that supports the possibility of motor plasticity in the networks controlling rhythmicity in PD and the potential for using RAS as an intervention to improve mobility and reduce fall risk.

Is freezing of gait in Parkinson's disease related to asymmetric motor function?

Freezing of gait (FOG) is a disabling phenomenon common in patients with advanced Parkinsons disease (PD). The cause of FOG is unclear. The objective of this study was to explore a novel hypothesis stating that FOG is related to asymmetric motor performance. We compared PD patients that experience FOG episodes (PD+FOG) with PD patients that do not (PD−FOG) and studied the relationship of FOG to asymmetry in gait and in rhythmic hand movement performance to determine whether potential FOG‐related gait asymmetry is unique to walking or whether it is systemic. Subjects were tested in an “off” (unmedicated) and again in an “on” (medicated) state. Gait was more asymmetric in PD+FOG than in PD−FOG during “off” state (p = 0.005) and during “on” (p = 0.016). Rhythmicity of foot swing in one leg was correlated with the other leg in PD−FOG but not in PD+FOG. There was no difference in asymmetry in performance of rhythmic hand movements between the two groups. No correlation was found between asymmetry of clinical symptoms and gait asymmetry. Taken together, the results of this study suggest that bilateral uncoordinated gait and marked gait asymmetry, but not asymmetry in motor performance in general, are associated with FOG. Ann Neurol 2005;57:656–663

Marked alterations in the gait timing and rhythmicity of patients with de novo Parkinson's disease

Little is known about the gait characteristics of subjects with de novo Parkinsons disease (PD). We hypothesized that alterations in the spatio‐temporal characteristics of gait will already be quantifiable in these patients. The gait of 35 patients with idiopathic PD (mean age 60 years) who were in the early stages of the disease (Hoehn and Yahr stage 1.8 ± 0.5, median 2.0, range 1.0–2.5) and were not yet treated with any anti‐parkinsonian medications were compared with the gait of age‐ and sex‐matched healthy controls (n = 22). The patients walked more slowly and with reduced swing times while also exhibiting increased left/right swing asymmetry and marked inconsistencies in the timing of gait. By contrast, significant group differences in the peak forces at heel‐strike and in the stride‐to‐stride variability of the ground reaction forces (a reflection of muscle output consistency) were not observed. These findings indicate that in de novo PD, an altered gait pattern is observed, even though dramatic changes in the gait pattern may not yet be apparent visually (e.g. fairly intact gait speed). Furthermore, the results demonstrate that the observed alterations are not just side‐effects of treatments or complications of the disease. Instead, there is evidence for motor programming deficits in gait, as revealed by increased gait variability and asymmetry in timing. PD apparently impinges on the regulation of a consistent gait rhythm, even early in the course of the disease when observed alterations are not the result of any pharmacologic treatment.

Freezing of gait affects quality of life of peoples with Parkinson's disease beyond its relationships with mobility and gait

The aim of this study was to examine the association between freezing of gait (FOG) and quality of life (QoL) in patients with Parkinsons disease (PD). PD patients (n = 118) completed the PDQ‐39 (QoL) and FOG‐Q questionnaires. Disease severity was assessed by the Hoehn and Yahr (H&Y) staging and the Unified Parkinsons Disease Rating Scale (UPDRS). The relations between those parameters were assessed using regression models. 66 men and 52 women (mean age 65.8 ± 10.2 years, UPDRS total score 48.4 ± 17.1, disease duration 8.5 ± 5.8 years, H&Y stage 2.7 ± 0.8) participated. FOG severity had a significant effect on QoL (P < 0.0015), accounting for disease severity assessed by UPDRS. Specifically, FOG severity was correlated with all the dimensions of the PDQ‐39 except for stigma and social support, as follows: with mobility, bodily discomfort, activity of daily living (ADL) (P < 0.005 in all), with emotional, communication, and cognition (P < 0.05 in all). FOG severity (FOG‐Q) was also found to affect a modified PDQ total score, without the mobility aspect (P = 0.0081). FOG should be viewed as a highly important symptom with regard to QoL of PD patients beyond its effect on gait and mobility. On the basis of the present results, special attention should be given to FOG in the treatment of patients with PD.

New onset heightened interest or drive for gambling, shopping, eating or sexual activity in patients with Parkinson's disease: the role of dopamine agonist treatment and age at motor symptoms onset

Alterations of impulse control that have recently been associated with Parkinsons disease (PD) are serious behavioural disturbances with significant impact on PD patients and their families. A total of 193 consecutive PD patients with no history of psychiatric illness and 190 age/gender-matched healthy controls were queried on the presence of new onset heightened interest or drive for gambling, shopping, eating or sexual activity (GSES). Clinical data were retrieved from medical charts and interviews. logistic regressions models assessed risk factors for these specific troublesome behaviours. New or heightened interests or drives for GSES behaviours were reported by 27 patients (14% vs 0% for controls). Younger age at PD motor symptoms onset (OR = 0.99, p = 0.0172), male gender (OR = 1.10, p = 0.0576) and longer duration of treatment with dopamine agonists (DAs)(OR = 1.18, ≥6 years versus never treated, p = 0.0459) contributed additively to the risk of developing one or more of these behavioural features. New onset heightened interests or drives for GSES are not rare behavioural disturbances among patients with PD. Age, gender and duration of treatment with DAs have an independent and additive effect on the risk to develop such behavioural changes. Patients should be informed about potential treatment-associated behavioural changes.

Assessing Fear of Falling: Can a Short Version of the Activities-Specific Balance Confidence Scale Be Useful?

We present the process of further validation of the 16‐item Activities‐specific Balance Confidence scale (ABC‐16) and a short version (ABC‐6) derived by us, to assess balance confidence and fear of falling (FOF). The ABC‐16 was administrated to three groups who were anticipated to have a range of balance confidence: 70 patients with higher level gait disorders (HLGDs), 68 healthy controls, and 19 patients with Parkinsons disease (PD). Item reduction was based on identifying items with the lowest scores (high FOF) among the patients. Internal consistency and discriminative validity were assessed using Cronbachs alpha and logistic regression, respectively. The intraclass correlation (ICC) between the short and long versions was assessed using a mixed model approach, accounting for the difference between the scores of the two versions. Six items were found to reflect the most frightening conditions, especially in the patient groups, and to form the short version (ABC‐6). Internal consistency of the ABC‐16 and ABC‐6 were high in the three groups: Cronbachs alpha was between 0.83 and 0.91 and 0.81 and 0.90, respectively. Compared to the control group, the sensitivity of the ABC‐16 was 96% for identification of patients with HLGDs (greatest FOF) and 58% for identification of PDs (moderate FOF), based only on the ABC scores. Similar values were obtained for the short version, i.e., 91% for HLGDs and 53% for PDs. ICCs between the short and the long versions was 0.88 (HLGDs), 0.83 (PDs), and 0.78 (Controls). To conclude, the short version of the ABC has properties analogous to the parent questionnaire and is apparently useful in assessing FOF.

Gait in attention deficit hyperactivity disorder : effects of methylphenidate and dual tasking.

BackgroundCognitive function and the loading of attention presumably play an important role in gait as well as in fall risk, but previous work has not demonstrated this in any cause-and-effect way.ObjectivesTo gain insight into the relationship between gait and cognitive function, we sought: (1) To compare the gait rhythmicity (stride time variability) of children with attention deficit hyperactivity disorder (ADHD) to controls, (2) To test the hypothesis that dual tasking leads to increased stride-to-stride variability in ADHD, and (3) To test whether pharmacological treatment that relieves ADHD symptoms reduces stride-to-stride variability.Patients and MethodsGait was quantified in children with ADHD and in age-matched healthy controls under single task and dual task conditions on three occasions: off medications (both groups) and, in the ADHD group, after double blinded, randomized administration of methylphenidate (MPH) or placebo.ResultsAt baseline, children with ADHD tended to walk with increased stride-to-stride variability compared to the controls during the single task condition (p = 0.09). During dual task walking, stride time variability was significantly reduced in the children with ADHD (p < 0.004), but not in the controls. In the children with ADHD, the placebo did not significantly affect stride-to-stride variability or the dual tasking response. In contrast, stride time variability was significantly reduced on MPH (p < 0.001) such that dual tasking no longer affected variability.ConclusionsThe present findings demonstrate alterations in the gait of children with ADHD, support a cause and effect link between cognitive function and gait, and suggest that enhancement of attention abilities may, in certain populations, improve gait rhythmicity.

Segmental noxious versus innocuous electrical stimulation for chronic pain relief and the effect of fading sensation during treatment

It is not clear whether segmental innocuous stimulation has a stronger analgesic effect than segmental noxious stimulation for chronic pain and whether the fading of current sensation during treatment interferes with the analgesic effect, as suggested by the gate control theory. Electrical stimulation (by way of Interferential Current) applied at the pain area (segmental) was administered to 4 groups of patients with osteoarthritis (OA) knee pain. Two groups were administered with noxious stimulation (30% above pain threshold) and two with innocuous stimulation (30% below pain threshold). In each group half of the patients received a fixed current intensity while the other half raised the intensity continuously during treatment whenever fading of sensation was perceived. Group 5 and 6 received sham stimulation and no treatment, respectively. The outcome measures were: chronic pain intensity, morning stiffness, range of motion (ROM), pain threshold and % pain reduction. Both noxious and innocuous stimulation significantly decreased chronic pain (P<0.001) and morning stiffness (P<0.01) and significantly increased pain threshold (P<0.001) and ROM (P<0.001) compared with the control groups. Nevertheless, noxious stimulation decreased pain intensity (P<0.05) and increased pain threshold (P<0.001) significantly more than innocuous stimulation. No differences in treatment outcomes were found between adjusted and unadjusted stimulation. (a) Interferential current is very effective for chronic OA knee pain, (b) segmental noxious stimulation produces a stronger analgesic effect than segmental innocuous stimulation, (c) the fading of sensation during treatment, does not decrease the analgesic effect. Possible mechanisms explaining the findings are discussed.