Attention modulates step initiation postural adjustments in Parkinson freezers.

BACKGROUND: In view of freezing of gait's circumstances of occurrence in Parkinson's disease, attentional resources appear to be involved in step initiation failure. Anticipatory postural adjustments (APAs) are essential because they allow unloading of the stepping leg and so create the conditions required for progression. Our main objective was to establish whether or not a change in attentional load during step initiation modulates APAs differently in patients with vs. without freezing of gait. METHODS: Three groups of 15 subjects were recruited: elderly people and parkinsonian patients with or without freezing of gait. Attention was modulated before step execution by means of an auditory oddball discrimination task with event-related potential recording. The primary endpoint was the occurrence of inappropriate APAs following the attentional task, i.e. APAs not followed by a step after an intercurrent auditory stimulus. RESULTS: In parkinsonian patients with freezing of gait, inappropriate APAs were recorded in 63% of the trials and were observed more frequently than in patients without freezing of gait (51%) and elderly controls (48%). Furthermore, inappropriate APAs in freezers were longer and more ample than in parkinsonian non-freezers and controls. Lastly, postural preparation was impaired in the parkinsonian patients. CONCLUSION: Our results indicate that allocation of attentional resources during step preparation influences the release of APAs differently in freezers and non-freezers. Modulating attentional load is partly responsible for triggering an inappropriate motor program. This difficulty in focusing attention or resisting interference may contribute (at least in part) to the gait initiation failure observed in parkinsonian freezers.

External globus pallidus stimulation modulates brain connectivity in Huntington's disease.

Positron emission tomography with O-15-labeled water was used to study at rest the neurophysiological effects of bilateral external globus pallidus (GPe) deep brain stimulation in patients with Huntington's disease (HD). Five patients were compared with a control group in the on and off states of the stimulator. External globus pallidus stimulation decreased neuronal activity and modulated cerebral connectivity within the basal ganglia-thalamocortical circuitry, the sensorimotor, and the default-mode networks. These data indicate that GPe stimulation modulates functional integration in HD patients in accordance with the basal ganglia-thalamocortical circuit model.

[Therapeutic strategies for Parkinson's disease]. / Les stratégies du traitement antiparkinsonien.

The remarkable efficacy of L-dopa on the akinesia, tremor and rigidity of Parkinson's disease is incontestable. It is responsible for the functional improvement and the regained quality of life. Unfortunately, after this classical "honeymoon" appear the "motor complications of dopamine therapy" (MCD), motor fluctuations and dyskinesia. Even more frequent and severe when the patient is young, it compromises the patient's autonomy. Certainly, the manipulation of L-dopa, the modification of its metabolism, and its association with an agonist permit amelioration but this is inconstant, imperfect and brief. The pulsatility of dopaminergic stimulation is the determinant physiopathological element in the genesis of MCD. New strategies of anti-Parkinsonian treatment find there within their justification. Some of them aim to treat the MCD: the high frequency electric stimulation of the sub-thalamic core is the most recent example. The criteria of selection for the electric stimulation should be respected in order to ensure its efficacy. These symptomatic treatments however, have no influence on the natural history of the disease and/or the affect on other dopaminergic systems. Perhaps hope should rather be placed in neuroprotection.

Ictal movement disorders and hypothalamic hamartoma.

We report the case of a woman presenting with unusual, symptomatic epilepsy related to a hypothalamic hamartoma, in the absence of mental retardation or precocious puberty. The seizures manifested themselves clinically as characteristic, paroxysmal movement disorders, such as choreic/ballistic movement. This type of phenomenon is rarely of epileptic origin: we thus suggest that the movement disorder observed here could be due to functional disorganization of the basal ganglia network by the epileptic discharge, causing loss of the inhibition of thalamic activity and thus allowing the occurrence of abnormal movements.

Effects of subthalamic nucleus stimulation on parkinsonian dysarthria and speech intelligibility.

Subthalamic stimulation is known to improve tremor, akinesia and rigidity in Parkinson's disease. However, other signs such as hypophonia and swallowing disorders can be relatively resistant to this technique. The effect on dysarthria remains unclear. The aim of this study was to investigate the effects of implantation of electrode and stimulation of the subthalamic nucleus (STN) on parkinsonian dysarthria. Seven patients were prospectively included. Electrodes (Medtronic) were implanted in both STN. The electrode contacts and stimulation parameters were adjusted to provide best relief of symptoms with fewest side effects. Assessment used global scales (Unified Parkinson Disease Rating Scale, UPDRS II and III), dyskinesia scale, exhaustive dysarthria assessment (bucco-facial movements, voice, articulation, intelligibility) and the 'dysarthria' item from the UPDRS III. Evaluations were performed in six conditions: before and three months after surgery (pre-op, post-op) stimulation turned off or on (off-stim, onstim), and without or with a suprathreshold levodopa dose (offdrug, on-drug). Performance level on the UPDRS III significantly improved following electrode implantation and stimulation. For dysarthria, modest beneficial effects were observed on several motor parameters, especially lip movements. Voice mildly improved, especially for the modulation in loudness and pitch. Articulation was not affected. Furthermore, intelligibility was slightly reduced in the on-stimulation condition, especially when patients received levodopa. At an individual level, negative effects on intelligibility were observed in two patients, and this was associated with a discrete increase in facial and trunk dyskinesias, but not with the electrode position or stimulation parameters. In conclusion, surgery had weak effects on dysarthria. Intelligibility can be worsened, especially in the on-drug condition. Thus, adaptation of the stimulation parameters can be difficult.

Effects of subthalamic nucleus stimulation and levodopa treatment on gait abnormalities in Parkinson disease.

BACKGROUND: Stimulation of the subthalamic nucleus is proposed for the treatment of patients presenting with severe Parkinson disease. The effect on gait is not clearly established. OBJECTIVES: To evaluate objectively the influence of bilateral subthalamic nucleus stimulation on gait in Parkinson disease and to compare it with the effects of levodopa treatment. METHODS: Ten patients underwent bilateral subthalamic nucleus stimulation. The preoperative and postoperative (3 months after surgery) clinical gait disturbances, as well as spatial and temporal gait parameters, were analyzed in off and on-drug conditions. The gait analysis was performed using a video motion analysis system (optoelectronic VICON system; Oxford Metrics, Oxford, England). RESULTS: In the off condition, there was an improvement after surgery for the total motor score and the gait subscore. In the on-drug condition, there was an improvement in levodopa-induced dyskinesias and the motor score, whereas the gait subscore was unchanged. For the gait parameters measured by the video motion analysis system system, there was also an improvement in the off condition and to a lesser extent in the on-drug condition. CONCLUSIONS: Our method allowed exact quantification of the benefit of surgery on gait parameters. Compared with the levodopa treatment, the effect of stimulation on gait kinematic parameters seems to be qualitatively similar but quantitatively different with a lower benefit on gait velocity and stride length. Concerning the pathophysiology of gait troubles in Parkinson disease, the deficit in control of stride length would be the fundamental deficit. The study underlines the possible role of the subthalamic nucleus on the stride length regulation.

Influence of pallidal stimulation and levodopa on gait and preparatory postural adjustments in Parkinson's disease.

In order to assess the influence of the bilateral internal globus pallidus (GPi) stimulation on gait and postural instability in Parkinson's disease (PD), we compared gait kinematic parameters and preparatory postural adjustments before and 3 months after stimulation in off- and on-drug conditions for seven patients. Gait kinematic parameters and displacements of centre of pressure (CP) and shoulder computed before a lateral raising task of the leg, were recorded using optoelectric Vicon system. Levodopa (L-dopa) induced a clear benefit for gait velocity (related to an increase of stride length) and also an increase of swing phase duration. GPi stimulation had a limited effect, since the increase of gait velocity was induced by a concomitant increase of stride length and cadence corresponding to a compensatory mechanism. The benefit on swing phase duration was also moderate. Displacements of CP were improved mainly by L-dopa. GPi stimulation and L-dopa had the same beneficial effect on the speed at which the CP was transferred back towards the support side, the ankle velocity, the onset time for ankle displacement, and the decrease of shoulder amplitude towards the support side, which reflects a better postural adjustment phase. This study, based on an objective method, revealed that chronic bilateral GPi stimulation may improve gait and preparatory postural adjustments in severe PD patients with a more limited effect than L-dopa.