Jean Daniel Guieu

Heart rate variability and Parkinson’s disease severity

Summary. Heart rate variability (HRV) decrease in Parkinson’s disease (PD) could only be a consequence of reduce motor activity besides of being a marker of cardiovascular dysautonomia. Under continuously recorded and standardised motor activity, we studied thirty patients compared to controls in 3 PD stages: group I: less than 2 year-evolution, slight impaired without L-dopa; group II: mildly impaired with L-dopa; group III: advanced PD with motor complications. No difference was observed between group I and controls. The diurnal low frequency power (LF) and the ratio of LF/high frequency (HF) power decreased in groups II and III. The nocturnal vagal indicators: HF power and pNN50 were decreased in group III. Those parameters were correlated with Off-drug-motor handicap, suggesting an evolutive HRV decrease with disease severity but not with On-drug-motor activity. The low LF despite the higher motor activity in group III, due to dyskinesias, suggested a defective cardiovascular up-regulation.

Ankle dorsiflexion delay can predict falls in the elderly.

The aim of this study was to investigate the kinematic and kinetic characteristics of walking in healthy non-faller elderly in order to develop predictive parameters for falls. A 1-year prospective trial was completed on a walking circuit with two integrated force platforms and an optoelectronic system for three-dimensional movement analysis. Gait was investigated in 54 volunteers who were healthy people over 60 who had not fallen in the previous year. The subjects were contacted 2-monthly over a period of 1 year. The results showed that 16 of the 54 people tested had fallen. There was no significant age difference between the group of fallers and the group of non-fallers. Fallers walked more slowly and tended to use a double support for a longer period of time. Fallers were less powerful but mainly showed fewer power and moment variations. The range of motion at the ankle and the hip was reduced. We noticed a change in the walking pattern, showing a delay in the dorsiflexion of the ankle at the swing phase. In conclusion, subclinical gait parameters occur in older people. The advent of neuromotor pattern alterations when walking is related to the tendency to fall. Ankle dorsiflexion delays, in particular, appear to be predictive of falls.

Motor evoked potentials to magnetic stimulation: technical considerations and normative data from 50 subjects.

SummaryMagnetic stimulation of the brain and cervical and lumbar spinal roots was performed on 50 healthy volunteers. Compound muscle action potentials (CMAPs) were recorded from biceps brachii, abductor digiti minimi (ADM), rectus femoris and tibiahs anterior (TA). We assessed central conduction times by subtraction of peripheral from central latencies and compared results using either spinal root stimulation or the F-wave method. Side-to-side differences of total conduction time, peripheral conduction time and central conduction time (CCT) were measured and the effect of clockwise vs counterclockwise stimulations on latencies and sizes of CMAPs is emphasized. Amplitudes and areas of CMAPs were expressed as a percentage of the peripheral M response for ADM and TA. There was a positive correlation between CCT to the lumbosacral region and height, but not between the cervical region and height. No correlation was observed between genders and central conduction times, amplitudes or areas of CMAPs.

P300 component of the event-related potentials (ERP) during an attention task: effects of age, stimulus modality and event probability

The effects of age, stimulus modality and event probability on event-related potentials (ERP) were studied in 12 young and 12 elderly healthy subjects. The ERP were recorded from 15 electrodes referred to linked ears. Results showed that both amplitude and latency of the P300 component are affected by aging. Study of the latency of the earlier ERP components in the two age groups revealed that the P300 delay was not imputable to a delay of the earlier components. P300 amplitude and latency were also affected by event probability and stimulus modality: infrequent stimulus involved higher and later P300, but this effect was more pronounced in the young than in the old group; higher and later P300 were also recorded during the visual task compared to the auditory. Topographical repartition of the brain wave revealed a predominance of the central sites (Fz, Cz, Pz). The findings are discussed in relation to the sensitivity of the ERP assessment procedures in age related modifications of information processing.

Chronic bilateral pallidal stimulation and levodopa do not improve gait in the same way in Parkinson's disease: a study using a video motion analysis system.

Abstract Chronic bilateral internal globus pallidus (GPi) stimulation allows control of levodopa induced dyskinesias (LID) and motor symptoms in severe Parkinsons disease (PD). The effect on gait has not been clearly established. Different results have been reported, mostly consisting of clinical data. The aim of this study was to evaluate, by means of a video motion analysis system (optoelectronic VICON system), the influence of bilateral GPi stimulation on gait in PD.Five patients underwent bilateral GPi stimulation. The preoperative and postoperative (3 months after surgery) clinical gait disturbances (items 29 and 30 of the motor UPDRS), as well as spatial and temporal gait measurements (namely cadence, velocity, stride and step times, single and double limb support times, stride and step lengths) were analysed in off condition (the patient had received no treatment for 12 hours or merely the lowest dose of levodopa allowing him to walk for the gait analysis) and in the on drug condition (after administration of 200 mg of levodopa). The gait analysis was performed with the VICON system.In off condition, there was a statistically significant improvement after surgery for UPDRS III and gait (clinically assessed). In on drug condition, there was a significant improvement for LID whereas UPDRS III and clinical assessment of gait were unchanged.The VICON system also showed that surgery improved gait especially in off condition, but also in on drug condition.Our method allowed exact quantification of the influence of surgery on gait characteristics. As compared with levodopa treatment, the effect of stimulation seems to be different. Indeed, the results suggest only limited effects of pallidal stimulation on the control of stride length and rather point to compensatory additional mechanisms.

Motor programming is more affected in progressive supranuclear palsy than in Parkinson's disease: A spatiotemporal study of event‐related desynchronization

To determine the benefit of motor programming analysis for distinguishing patients with parkinsonism, we compared the spatiotemporal pattern of event‐related desynchronization (ERD) preceding a self‐paced voluntary wrist flexion between two groups of 10 patients with progressive supranuclear palsy (PSP) and Parkinsons disease (PD) and 10 control subjects. ERD of the mu rhythm was computed from 11 source derivations covering the medial frontocentral, central, and parietocentral areas during two successive left and right experimental conditions (80 self‐paced wrist flexions). ERD began in the control group 1750 ms before movement onset over the contralateral central area and then appeared bilaterally on movement execution. In both patient groups, spatiotemporal distribution differed from that in the control group. In the PSP group, ERD had a shorter latency over the contralateral primary sensorimotor area compared with the PD group (PSP: 375 ms before movement onset for both conditions; PD: right flexion 1125 ms before movement onset, left flexion 1000 ms). ERD was observed over the parietocentral area in both groups but also with a clear reduction of latency before movement onset in the PSP group. In both groups, a bilateral central pattern appeared 250 ms before movement execution. In conclusion, our study indicates that ERD analysis is a useful method for observing the changes in cortical activation and for measuring motor programming impairment in parkinsonism, which was more affected in PSP than in PD.