P. Krystkowiak

Subthalamic nucleus stimulation induces deficits in decoding emotional facial expressions in Parkinson’s disease

Background: Bilateral subthalamic nucleus (STN) stimulation is recognised as a treatment for parkinsonian patients with severe levodopa related motor complications. Although adverse effects are infrequent, some behavioural disturbances have been reported. Objective: To investigate the consequences of STN stimulation on emotional information processing in Parkinson’s disease by assessing the performance of an emotional facial expression (EFE) decoding task in a group of patients before and after surgery. Methods: 12 non-demented patients with Parkinson’s disease were studied. They were assessed one month before surgery and three months after. Their ability to decode EFEs was assessed using a standardised quantitative task. Overall cognitive function, executive function, visuospatial perception, depression, and anxiety were also measured. Twelve healthy controls were matched for age, sex, and duration of education. Results: Before surgery, the patients showed no impairment in EFE decoding compared with the controls. Their overall cognitive status was preserved but they had a moderate dysexecutive syndrome. Three months after surgery, they had significant impairment of EFE decoding. This was not related to their overall cognitive status or to depression/anxiety scores. Visuospatial perception was not impaired. There was no change in the extent of the dysexecutive syndrome except for a reduction in phonemic word fluency. Conclusions: Bilateral STN stimulation disturbs negative emotional information processing in Parkinson’s disease. The impairment appears specific and unrelated to certain secondary variables. This behavioural complication of STN may have implications for the patient’s social life.

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 Parkinsons 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.

Are gait initiation parameters early markers of Huntington's disease in pre-manifest mutation carriers?

Huntingtons disease (HD) pre-manifest mutation carriers (PMCs) present early-onset gait disturbances. Gait initiation encompasses the preparation and execution of the first step. By using paradigms with and without external cues, a gait initiation analysis can highlight the interaction between motor and cognitive aspects of movement preparation and execution. Hence, gait initiation disorders may constitute particularly interesting early markers of HD. The objective of the present study was to quantify gait initiation in PMCs. In a case-control study, 17 PMCs (median age: 36.5) were compared with a group of 25 healthy controls (HCs, median age: 36) for gait initiation and a group of 57 HCs (median age: 38) for gait. Presymptomatic mutation carriers displayed a shorter first step duration and lower-amplitude postural adjustments. For the first step duration and speed, these impairments were more pronounced under self-triggered (ST) conditions. The PMCs displayed a lower gait speed, cadence and stride length and higher stride-to-stride variability. The latter parameter seemed capable of differentiating between PMCs and HCs with adequate sensitivity (0.81) and specificity (0.87). We confirmed the early-onset impairment of gait in general and first step execution in particular in PMCs (particularly under ST conditions). The temporal parameters of step execution (e.g. duration) and spatial parameters of postural adjustment (e.g. a backward shift in the centre of pressure) may be worth investigating as early markers of HD. However, two such parameters (stride-to-stride variability and first step duration under ST conditions) already appear to be sufficiently reliable diagnostic tools for differentiating between PMCs and HCs.