Maladaptive One-Leg Balance Control in Parkinson’s Disease

Balance disorders are very frequent in Parkinson’s disease (PD). One-leg stance performance is a predictor of fall risk. We investigated one-leg stance strategies in people with PD. We hypothesized that patients would choose, and better perform on, the leg on the least affected body side. Fifty participants with 2 to 19 years of PD duration stood on one leg while ON medication. The leg spontaneously chosen was recorded. Performance was compared between the spontaneously chosen vs. contralateral, and most vs. least stable legs. Influence of disease duration, severity, age, cognition, and motor fluctuations was analyzed. Twenty-eight patients spontaneously stood on the leg of the least affected body side, which was not always the most stable one. The chosen standing leg was influenced by disease duration with a switch between the least vs. most affected body side after seven years of disease duration. Fourteen patients (28%) spontaneously stood on their least stable leg. Thus, some patients with PD choose the least stable leg when asked to perform one-leg stance. It is important to identify these patients since they may be at greater risk of falls and/or gait difficulties. Specific rehabilitation may help prevent such maladaptive strategy

Motricité, cognition, émotion dans la maladie de Parkinson : rôle des oscillations du noyau subthalamique

Deep brain stimulation may be used to study the oscillatory activity of the subthalamic nucleus (STN) local field potentials in Parkinson's disease (PD) patients. The aim of this study was to characterize the STN oscillatory activity during voluntary movements, executive functions and emotion perception. Our results show that akinesia is associated and correlated with beta band hypersynchronization recorded in the dorsolateral part of the STN. The beta band oscillatory activity differs within decision making, inhibition and movement preparation functions. The default of emotion perception is associated with a lack of alpha band synchronisation in OFF dopaminergic medication condition. Levodopa modulates, at least partly, the oscillatory activities of the motor, executive and emotional basal ganglia functional pathways. The alpha, beta and gamma oscillatory activities are balanced in the normal functioning of the neuronal networks.La maladie de Parkinson constitue un modèle de fonctionnement et d'étude des ganglions de la base (GB). Le traitement par stimulation du noyau subthalamique (NST) offre l'opportunité d'enregistrer in vivo l'activité électrophysiologique des potentiels de champs locaux dans les fonctions mettant en jeu les boucles motrice, préfrontale dorsolatérale et limbique des GB. L'akinésie est associée à une hypersynchronisation dans la bande de fréquence bêta prédominant dans la partie dorsolatérale du NST, corrélée au degré d'akinésie. Les tâches de prise de décision et d'inhibition sont associées à une activité bêta différente des tâches de préparation et d'attente réflexe. L'altération de la perception de stimuli à contenu émotionnel est associée à un défaut de synchronisation alpha. La lévodopa module partiellement ces activités oscillatoires. Une balance entre les activités alpha, bêta et gamma constituerait le mode de fonctionnement normal des réseaux neuronaux

Effects of varying subthalamic nucleus stimulation on apraxia of lid opening in Parkinson's disease

Apraxia of lid opening (ALO) is a non-paralytic inability to open the eyes or sustain lid elevation at will. The exact pathophysiological mechanisms underlying the syndrome are still unknown. ALO has been reported in patients with Parkinson's disease (PD) after subthalamic nucleus (STN) deep brain stimulation (DBS), suggesting a possible involvement of the basal ganglia. We aimed to assess the effects of varying STN stimulation voltage on ALO in PD patients. Seven out of 14 PD patients with bilateral STN stimulation consecutively seen in our centre presented with ALO. We progressively increased voltage on each STN, using either 130 Hz (high-frequency stimulation, HFS) or 2 or 3 Hz (low-frequency stimulation, LFS). In five patients, HFS induced ALO time-locked to stimulation in 7 out of 10 STNs at a voltage higher than that used for chronic stimulation. LFS induced myoclonus in the pretarsal orbicularis oculi muscle (pOOm) with a rhythm synchronous to the frequency. In the other two patients with ALO already present at the time of the study, HFS improved ALO in 3 out of 4 STNs. ALO recurred within minutes of stimulation arrest. Our findings show that STN-DBS can have opposite effects on ALO. On the one hand, ALO is thought to be a corticobulbar side effect due to lateral current spreading from the STN, in which case it is necessary to use voltages below the ALO-inducing threshold. On the other hand, ALO may be considered a form of off-phase focal dystonia possibly improved by increasing the stimulation voltages

Effects of subthalamic nucleus stimulation on motor cortex excitability in Parkinson's disease.

International audienceOBJECTIVE: To study the effects of subthalamic nucleus (STN) stimulation on motor cortex excitability in Parkinson's disease (PD). METHODS: Fifteen patients were evaluated under off-medication, OFF- and ON-STN conditions, using the UPDRS. We studied the effects of STN stimulation on motor cortex excitability under three conditions (OFF, ON with chronic therapeutic parameters, ON HighV with a voltage set 10% under permanent side effects threshold), using transcranial magnetic stimulation. We measured the central motor conduction time (CMCT), rest and active motor threshold (MT), F-wave persistence and amplitude, silent period (SP), intracortical inhibition and facilitation at 3, 5 and 15 ms interstimulus intervals (ISI). RESULTS: The UPDRS motor score decreased from 44.4+/-14.0 under OFF, to 15.2+/-8.0 under ON-STN condition. The CMCT and MT did not change across STN conditions. The F-wave parameters were within normal range under STN stimulation. STN stimulation lengthened the SP and induced facilitation at 15 ms ISI compared to the OFF-STN condition. CONCLUSION: Therapeutic STN stimulation modulates cortical excitability in PD. High voltage STN stimulation could also act on spinal excitability. SIGNIFICANCE: At the motor cortical level, STN stimulation may have a direct effect on intracortical interneurons, modifying the balance between excitation and inhibition

Bilateral subthalamic stimulation effects on oral force control in Parkinson's disease

International audienceDysarthria in Parkinson's disease (PD) consists of articulatory, p honatory and respiratory impairment. Bilateral subthalamic nucleus (STN) stimulation greatly improves motor disability,b ut its long-term effect on speech within a large group of patients has not been precisely evaluated. The aim of this study was to determine the effect of bilateral STN stimulation on oral force control in PD.We measured forces of the upper lip, lower lip and tongue in twenty-six PD patients treated with bilateral STN stimulation.Measurements of the articulatory organ force,as well as a motor evaluation using the Unified Parkinson's Disease Rating Scale (UPDRS),were made with and without STN stimulation.Maximal voluntary force (MVF),reaction time (RT),movement time (MT),im precision of the peak force (PF) and the hold phase (HP) were all improved with STN stimulation during the articulatory force task, as well as the motor examination scores of the UPDRS. It seems that the beneficial STN stimulation-induced effect on articulatory forces persisted whatever the duration of post-surgical follow-up.However, dysarthria evaluated by the UPDRS was worse in two subgroups of patients with a one to two year and three to five year post-surgical follow- up,in comparison with a subgroup of patients with a three month follow-up. STN stimulation has a beneficial long-term effect on the articulatory organs involved in speech production,and this indicates that parkinsonian dysarthria is associated,a t least in part,w ith an alteration in STN neuronal activity. Nevertheless,t o confirm the persistence of the beneficial effect of STN stimulation on parkinsonian dysarthria,a longitudinal evaluation is still needed

Lifetime of Itrel II pulse generators for subthalamic nucleus stimulation in Parkinson's disease.

International audienceThe efficacy of bilateral subthalamic nucleus (STN) stimulation in Parkinson's disease (PD) is well-established but little is known about the lifetime of implanted pulse generators (IPG). To investigate the lifetime of the bilaterally implanted Itrel II(R) (Medtronic, Minneapolis) pulse generator, the first 49 consecutive patients with PD having been operated on at our center for bilateral STN chronic stimulation were reviewed with noting of the stimulation parameters in use prior to IPG replacement. The mean electrical voltage was 3.2 +/- 0.3 V, mean pulse width was 65 +/- 10 mus, and mean frequency was 145 +/- 16 Hz. Replacement of an IPG was anticipated in 25% due to unilateral low-battery signaling, or end of life. In either case, replacement of the contralateral IPG was undertaken simultaneously. The mean IPG lifetime was 83 +/- 14 [40-113] months. The IPG lifetime correlated with the total electrical energy delivered (P = 0.002, r = -0.496). Unilateral IPG end-of-life generally led to subacute worsening of contralateral parkinsonism. In 25% of patients, there was also a worsening of axial symptoms leading to potential medical emergencies such as falls (10%), aspiration pneumonia (10%), or psychosis (5%). A close monitoring of patients and an anticipation of IPG replacement in the case of a low-battery signal are recommended