Effect of chronic bilateral subthalamic nucleus (STN) stimulation on postural control in Parkinson's disease

Abstract

Postural instability is one of the most incapacitating factors in Parkinson's disease (PD). The underlying deficits and the effects of treatment are still not well understood. The aims of the present study were: (i) to identify abnormalities of postural control in PD patients during unperturbed stance and externally perturbed stance (anterior-posterior tilts of the support surface and of the visual scene); (ii) to assess the effects of L-dopa medication and subthalamic nucleus (STN) stimulation on posture control; and (iii) to characterize potential differential or additive effects of both treatments. Eight PD patients under chronic STN stimulation were investigated and compared with 10 normal controls. The assessment was performed in a crossover design (+/- STN stimulation, +/- L-dopa). During unperturbed stance, we recorded measures of spontaneous sway in terms of displacement, velocity and frequency of the centre of pressure (COP), lower body (LB) and upper body (UB) excursions. In addition, inter-segmental UB-LB coupling was investigated as a measure of axial stiffness. All these measures were abnormally large in patients OFF treatment. Under L-dopa treatment, the velocity, frequency and coupling measures were reduced, whereas sway amplitude increased. Very similar effects were obtained under STN stimulation, and these effects became more pronounced in the combined treatment condition. In these data, reduction of inter-segmental coupling correlated with increase in sway amplitude. The finding suggests that axial stiffness reduction under treatment revealed a treatment- resistant deficit in the sensorimotor postural control loop. However, these two effects did not correlate with the motor subscores of the unified Parkinson's disease rating scale (UPDRS), which indicates that they are of minor functional relevance for posture control. A frequency peak in the COP excursions at 0.7-1.1 Hz, which we take to indicate a resonance behaviour of the postural control loop, became reduced under therapy. The reduction of this peak did correlate with most improvements in the UPDRS under therapy. Support surface tilt revealed that an UB righting on the LB segment, which is present in normal controls, is missing in the patients. The postural responses to visual tilt were abnormally large in patients, independent of whether the support was stable or slightly moving, while the control subjects clearly profited from a stable support. This finding suggests that PD patients lack the ability of normal subjects to use sensory or cognitive information when suppressing the destabilizing effect of visual tilt. These abnormal tilt reactions of the patients were resistant to treatment with L-dopa, STN stimulation and a combination of the two. Overall, the effects of STN stimulation on posture control essentially paralleled those of L-dopa during both unperturbed and externally perturbed stance.

Falls and freezing of gait in Parkinson's disease: A review of two interconnected, episodic phenomena

“…59,[95][96][97][98] Bilateral interventions seem more effective than unilateral interventions, 99,100 and the effects were generally greatest for off state axial symptoms. A recent meta-analysis showed that bilateral pallidal stimulation and bilateral subthalamic nucleus stimulation were significantly more effective than unilateral pallidotomy in reducing gait and balance impairment during the off state.…”

The contribution of each leg to bipedal balance control : it takes two

“…That is, the cross terms of the FRFs were not significantly different from controls in PD patients. In contrast, an increased intersegmental coupling has been proposed by Maurer and colleagues (Maurer et al, 2003), but they studied a much smaller group of only eight patients that differed markedly from the patients in our sample: their patients were more severely affected and had been treated with STN-DBS.…”

“…It has been suggested that PD patients have a decreased intersegmental coordination (Maurer et al, 2003;Termoz et al, 2008) or an increased hip stiffness . In this study, the most pronounced difference between the healthy controls and the PD patients was found in the…”

“…Previous mentioned studies used either no external balance perturbations (Termoz et al, 2008), or only one perturbation ; Colnat-Coulbois et al, 2011; Kim et al, 2009;Maurer et al, 2003). However, to determine multisegmental balance control mechanisms, it may be better to use two perturbations .…”

Aplicação das Análises Biomecânicas da Pressão Plantar na Marcha de Indivíduos com Doença de Parkinson

“…A estabilidade postural, uma habilidade física associada ao controle postural e importante para a execução segura de atividades diárias, foi avaliada através da área de oscilação do COP na posição estática, em indivíduos após ECP-NST 22 , revelando que a associação entre ECP--NST e a fase on do tratamento dopaminérgico mostrou os maiores ganhos na estabilidade postural. A ECP-NST também mostrou-se capaz de provocar aumento no comprimento da passada e na velocidade da marcha, habilidades que normalmente apresentam-se com valores reduzidos em pacientes com DP, e este incremento foi maior quando associado ao tratamento dopaminérgico 23 .…”