Split-belt locomotion in Parkinson's disease with and without freezing of gait.

BACKGROUND: Parkinson's disease (PD) patients have an increased gait asymmetry and variability, which is most pronounced in patients with freezing of gait (FOG). We examined if stride time variability and deficits in interlimb coordination between the upper and lower limbs would increase during split-belt locomotion in PD, and particularly so in patients with FOG. METHODS: Fourteen PD patients (seven with FOG, matched for disease severity with the seven non-freezers) and 10 healthy controls walked on a treadmill with split belts at different speeds (2 versus 3km/h). Gait was recorded by means of a video motion analysis system. Outcome measures were stride length asymmetry and variability, stride time asymmetry and variability, ipsilateral and contralateral interlimb coordination, and phase coordination index. RESULTS: Both PD subjects and controls were able to adapt to split-belt walking by modulating their stride length. However, freezers showed a larger increase in stride time asymmetry and stride time variability due to split-belt walking compared to non-freezers. Furthermore, contralateral interlimb coordination improved in control subjects during split-belt walking, but not in PD patients (freezers and non-freezers). Phase coordination index did not change differently across the three groups. CONCLUSIONS: The ability to walk under split-belt conditions was preserved in PD. Non-freezers and controls compensated for the experimentally increased stride length asymmetry by decreasing their stride time asymmetry. This ability was lost in freezers, who in fact increased their stride time asymmetry during split-belt walking. As a result, stride time variability also increased in freezers. These findings support the hypothesis that FOG is related to gait asymmetries and to gait timing deficits.

The effects of vibrotactile biofeedback training on trunk sway in Parkinson's disease patients.

BACKGROUND: Postural instability in Parkinson's disease (PD) can lead to falls, injuries and reduced quality of life. We investigated whether balance in PD can improve by offering patients feedback about their own trunk sway as a supplement to natural sensory inputs. Specifically, we investigated the effect of artificial vibrotactile biofeedback on trunk sway in PD. METHODS: Twenty PD patients were assigned to a control group (n = 10) or biofeedback group (n = 10). First, all patients performed two sets of six gait tasks and six stance tasks (pre-training assessment). Subsequently, all subjects trained six selected tasks five times (balance training). During this training, the feedback group received vibrotactile feedback of trunk sway, via vibrations delivered at the head. After training, both groups repeated all twelve tasks (post-training assessment). During all tasks, trunk pitch and roll movements were measured with angular velocity sensors attached to the lower trunk. Outcomes included sway angle and sway angular velocity in the roll and pitch plane, and task duration. RESULTS: Overall, patients in the feedback group had a significantly greater reduction in roll (P = 0.005) and pitch (P < 0.001) sway angular velocity. Moreover, roll sway angle increased more in controls after training, suggesting better training effects in the feedback group (P < 0.001). CONCLUSIONS: One session of balance training in PD using a biofeedback system showed beneficial effects on trunk stability. Additional research should examine if these effects increase further after more intensive training, how long these persist after training has stopped, and if the observed effects carry over to non-trained tasks.

First trial reactions and habituation rates over successive balance perturbations in Parkinson's disease.

BACKGROUND: Balance control in Parkinson's disease is often studied using dynamic posturography, typically with serial identical balance perturbations. Because subjects can learn from the first trial, the magnitude of balance reactions rapidly habituates during subsequent trials. Changes in this habituation rate might yield a clinically useful marker. We studied balance reactions in Parkinson's disease using posturography, specifically focusing on the responses to the first, fully unpractised balance disturbance, and on the subsequent habituation rates. METHODS: Eight Parkinson patients and eight age- and gender-matched controls received eight consecutive toe-up rotations of a support-surface. Balance reactions were measured with a motion analysis system and converted to centre of mass displacements (primary outcome). RESULTS: Mean centre of mass displacement during the first trial was 51% greater in patients than controls (P=0.019), due to excessive trunk flexion and greater ankle plantar-flexion. However, habituated trials were comparable in both groups. Patients also habituated slower: controls were fully habituated at trial 2, whereas habituation in patients required up to five trials (P=0.004). The number of near-falls during the first trial was significantly correlated with centre of mass displacement during the first trial and with habituation rate. CONCLUSIONS: Higher first trial reactions and a slow habituation rate discriminated Parkinson's patients from controls, but habituated trials did not. Further work should demonstrate whether this also applies to clinical balance tests, such as the pull test, and whether repeated delivery of such tests offers better diagnostic value for evaluating fall risks in parkinsonian patients.

Walking patterns in Parkinson's disease with and without freezing of gait.

The pathophysiology underlying freezing of gait (FOG) in Parkinson's disease remains incompletely understood. Patients with FOG ("freezers") have a higher temporal variability and asymmetry of strides compared to patients without FOG ("non-freezers"). We aimed to extend this view, by assessing spatial variability and asymmetry of steps and interlimb coordination between the upper and lower limbs during gait. Twelve freezers, 15 non-freezers, and 15 age-matched controls were instructed to walk overground and on a treadmill. Kinematic data were recorded with a motion analysis system. Both freezers and non-freezers showed an increased spatial variability of leg movements compared to controls. In addition, both patient groups had a deficit in interlimb coordination, not only between ipsilateral arms and legs, but also between diagonally positioned limbs. The only difference between freezers and non-freezers was a decreased step length during treadmill walking. We conclude that parkinsonian gait-regardless of FOG-is irregular, not only in the legs, but also with respect to interlimb coordination between the arms and legs. FOG is reflected by abnormal treadmill walking, presumably because this provides a greater challenge to the defective supraspinal control than overground walking, hampering the ability of freezers to increase their stride length when necessary.