Apomorphine delays simple reaction time in Parkinsonian patients

Feasibility of using the Leap Motion Controller to administer conventional motor tests: a proof-of-concept study

Although upper-limb movement impairments are common, the primary tools for assessing and tracking impairments in clinical settings are limited. Markerless motion capture (MMC) technology has the potential to provide a large amount of quantitative, objective movement data in routine clinical use. Many past studies have focused on whether MMC are sufficiently accurate. However, another necessary step is to create meaningful clinical tests that can be administered via MMC in a robust manner. Four conventional upper-limb motor tests common in clinical assessments (visually guided movement, finger tapping, postural tremor, and reaction time) were modified so they can be administered via a particular MMC sensor, the Leap Motion Controller (LMC). In this proof-of-concept study, we administered these modified tests to 100 healthy subjects and present here the successes and challenges we encountered. Subjects generally found the LMC and the graphical user interfaces of the tests easy to use. The LMC recorded movement with sufficiently high sampling rate (>106 samples/s), and the rate of LMC malfunctions (mainly jumps in time or space) was low, so only 1.9% of data was discarded. However, administration of the tests also revealed some significant weaknesses. The visually guided movement test was easily implemented with the LMC; the modified reaction time test worked reasonably well with the LMC but is likely more easily implemented with other existing technologies; and the modified tremor and finger tapping tests did not work well because of the limited bandwidth of the LMC. Our findings highlight the need to develop and evaluate motor tests specifically suited for MMC. The real strength of MMC may not be in replicating conventional tests but rather in administering new tests or testing conditions not possible with conventional clinical tests or other technologies.

EuroInf 2: Subthalamic stimulation, apomorphine, and levodopa infusion in Parkinson's disease

OBJECTIVE

Real-life observational report of clinical efficacy of bilateral subthalamic stimulation (STN-DBS), apomorphine (APO), and intrajejunal levodopa infusion (IJLI) on quality of life, motor, and nonmotor symptoms (NMS) in Parkinson's disease (PD).

METHODS

In this prospective, multicenter, international, real-life cohort observation study of 173 PD patients undergoing STN-DBS (n = 101), IJLI (n = 33), or APO (n = 39) were followed-up using PDQuestionnaire-8, NMSScale (NMSS), Unified PD Rating Scale (UPDRS)-III, UPDRS-IV, and levodopa equivalent daily dose (LEDD) before and 6 months after intervention. Outcome changes were analyzed with Wilcoxon signed-rank or paired t test when parametric tests were applicable. Multiple comparisons were corrected (multiple treatments/scales). Effect strengths were quantified with relative changes, effect size, and number needed to treat. Analyses were computed before and after propensity score matching, balancing demographic and clinical characteristics.

RESULTS

In all groups, PDQuestionnaire-8, UPDRS-IV, and NMSS total scores improved significantly at follow-up. Levodopa equivalent daily dose was significantly reduced after STN-DBS. Explorative NMSS domain analyses resulted in distinct profiles: STN-DBS improved urinary/sexual functions, mood/cognition, sleep/fatigue, and the miscellaneous domain. IJLI improved the 3 latter domains and gastrointestinal symptoms. APO improved mood/cognition, perceptual problems/hallucinations, attention/memory, and the miscellaneous domain. Overall, STN-DBS and IJLI seemed favorable for NMSS total score, and APO favorable for neuropsychological/neuropsychiatric NMS and PDQuestionnaire-8 outcome.

CONCLUSIONS

This is the first comparison of quality of life, nonmotor. and motor outcomes in PD patients undergoing STN-DBS, IJLI, and APO in a real-life cohort. Distinct effect profiles were identified for each treatment option. Our results highlight the importance of holistic nonmotor and motor symptoms assessments to personalize treatment choices. © 2019 International Parkinson and Movement Disorder Society.

Neurophysiological mechanisms of circadian cognitive control in RLS patients - an EEG source localization study

The circadian variation of sensory and motor symptoms with increasing severity in the evening and at night is a key diagnostic feature/symptom of the restless legs syndrome (RLS). Even though many neurological diseases have shown a strong nexus between motor and cognitive symptoms, it has remained unclear whether cognitive performance of RLS patients declines in the evening and which neurophysiological mechanisms are affected by the circadian variation. In the current study, we examined daytime effects (morning vs. evening) on cognitive performance in RLS patients (n = 33) compared to healthy controls (n = 29) by analyzing flanker interference effects in combination with EEG and source localization techniques. RLS patients showed larger flanker interference effects in the evening than in the morning (p = .023), while healthy controls did not display a comparable circadian variation. In line with this, the neurophysiological data showed smaller N1 amplitudes in RLS patients compared to controls in the interfering task condition in the evening (p = .042), but not in the morning. The results demonstrate diurnal cognitive changes in RLS patients with intensified impairments in the evening. It seems that not all dopamine-regulated cognitive processes are altered in RLS and thus show daytime-dependent impairments. Instead, the daytime-related cognitive impairment emerges from attentional selection processes within the extra-striate visual cortex, but not from later cognitive processes such as conflict monitoring and response selection.

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RLS patients have larger flanker interference effect in the evening.

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RLS patients have enhanced impairment of attentional selection in the evening.

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Nocturnal attentional impairment relies on the extra-striate visual cortex.

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Conflict monitoring and response selection are not affected by RLS.

Parkinson's disease, visual hallucinations and apomorphine: A review of the available evidence

BACKGROUND

Visual hallucinations (VH) occur in the clinical course of Parkinson's disease (PD) and are predictive for PD dementia. The genesis of VH is related to impaired bottom-up and/or top-down visual processing which can be linked to cholinergic dysfunction and mono-amine imbalance. The risk of developing VH with oral dopamine agonists seems to increase with advancing disease, while in contrast some clinical studies suggest that apomorphine does not worsen VH, or might even improve VH.

METHODS

The aim of this study is to review the current evidence of apomorphine and its effects on VH in PD patients.

RESULTS

Apomorphine is well-tolerated in PD patients with VH, also in long-term follow-up studies. Apomorphine is also suggested to have the potential to alleviate VH. Some data suggest that the positive effect of apomorphine on VH is related to its piperidine moiety, part of many anti-psychotics. Irrespective this piperidine moiety, apomorphine has a high D1-like receptor affinity, and acts as a serotonin 5-HT2A receptor antagonist, which might explain the potential anti-hallucinogenic properties as well.

CONCLUSION

The anecdotal evidence suggesting that apomorphine has a relatively low proclivity to induce VH in PD may be due to its capacity to reduce serotonergic activity in particular. Therefore apomorphine is still an option to consider in fluctuating PD patients with VH, if they are treated properly with respect to their cholinergic deficits and existing VH.

Amelioration of non-motor dysfunctions after transplantation of human dopamine neurons in a model of Parkinson's disease

Background

Patients suffering from Parkinson's disease (PD) display cognitive and neuropsychiatric dysfunctions, especially with disease progression. Although these impairments have been reported to impact more heavily upon a patient's quality of life than any motor dysfunctions, there are currently no interventions capable of adequately targeting these non-motor deficits.

Objectives

Utilizing a rodent model of PD, we investigated whether cell replacement therapy, using intrastriatal transplants of human-derived ventral mesencephalic (hVM) grafts, could alleviate cognitive and neuropsychiatric, as well as motor, dysfunctions.

Methods

Rats with unilateral 6-hydroxydopamine lesions to the medial forebrain bundle were tested on a complex operant task that dissociates motivational, visuospatial and motor impairments sensitive to the loss of dopamine. A subset of lesioned rats received intrastriatal hVM grafts of ~ 9 weeks gestation. Post-graft, rats underwent repeated drug-induced rotation tests and were tested on two versions of the complex operant task, before post-mortem analysis of the hVM tissue grafts.

Results

Post-graft behavioural testing revealed that hVM grafts improved non-motor aspects of task performance, specifically visuospatial function and motivational processing, as well as alleviating motor dysfunctions.

Conclusions

We report the first evidence of human VM cell grafts alleviating both non-motor and motor dysfunctions in an animal model of PD. This intervention, therefore, is the first to improve cognitive and neuropsychiatric symptoms long-term in a model of PD.

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Non-motor dysfunctions affect quality of life in Parkinson's disease.

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We tested whether human-derived foetal dopamine cells could improve these deficits.

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Human dopamine cells improved rotational bias and movement impairments in a rat model.

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Non-motor dysfunctions, specifically visuospatial and motivational deficits, improved.

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This is the first evidence of improved non-motor deficits from human dopamine cells.

Acute and chronic cognitive effects of levodopa and dopamine agonists on patients with Parkinson's disease: a review

The spatiotemporal progression of dopamine depletion in Parkinson's disease (PD) provides a special model for assessing dopaminergic effects on neural systems with differential baseline dopamine levels. This study aims at reviewing cognitive effects of dopaminergic stimulation in PD. While considering dopaminergic drugs (levodopa or dopamine agonists), temporal intervals (acute or chronic) and cognitive domains, we found that empirical evidence was almost focused on acute effects of levodopa on executive functions. The paucity of empirical evidence suggests that no meaningful conclusions can be actually drawn and further research is needed in relation to: (1) other cognitive domains; (2) the acute cognitive effects of dopamine agonists, as compared with levodopa; (3) possible differences between cognitive effects of different dopamine agonists; (4) the cognitive effects of chronic dopaminergic therapies. The latter issue is of particular clinical interest considering that many PD patients present a mild cognitive impairment: is this cognitive feature worsened or improved by the prolonged dopaminergic therapy? In addition to the potential risk of inducing dyskinesia and behavioral side effects such as impulse control disorders, also cognitive effects of prolonged dopaminergic treatments should be taken in account by clinicians in order to anticipate or to delay their prescription to PD patients.

Differential effects of dopaminergic therapies on dorsal and ventral striatum in Parkinson's disease: implications for cognitive function

Cognitive abnormalities are a feature of Parkinson's disease (PD). Unlike motor symptoms that are clearly improved by dopaminergic therapy, the effect of dopamine replacement on cognition seems paradoxical. Some cognitive functions are improved whereas others are unaltered or even hindered. Our aim was to understand the effect of dopamine replacement therapy on various aspects of cognition. Whereas dorsal striatum receives dopamine input from the substantia nigra (SN), ventral striatum is innervated by dopamine-producing cells in the ventral tegmental area (VTA). In PD, degeneration of SN is substantially greater than cell loss in VTA and hence dopamine-deficiency is significantly greater in dorsal compared to ventral striatum. We suggest that dopamine supplementation improves functions mediated by dorsal striatum and impairs, or heightens to a pathological degree, operations ascribed to ventral striatum. We consider the extant literature in light of this principle. We also survey the effect of dopamine replacement on functional neuroimaging in PD relating the findings to this framework. This paper highlights the fact that currently, titration of therapy in PD is geared to optimizing dorsal striatum-mediated motor symptoms, at the expense of ventral striatum operations. Increased awareness of contrasting effects of dopamine replacement on dorsal versus ventral striatum functions will lead clinicians to survey a broader range of symptoms in determining optimal therapy, taking into account both those aspects of cognition that will be helped versus those that will be hindered by dopaminergic treatment.

Lower limb reaction time discriminates between multiple and single fallers

Despite research supporting its validity in predicting falls, simple reaction time (SRT) is not typically included in a clinical falls assessment battery because there is no standardised, clinically feasible testing protocol with published cutoff scores. This study aimed to determine whether SRT scores obtained using a clinically viable protocol could discriminate between multiple and single fallers. SRT scores were obtained from 147 participants (88 women and 59 men) over the age of 65 years (mean 80.1 years; SD 8.4 years) who had reported one or more falls in the previous 12 months. Forty-eight single and 99 multiple fallers were recruited from the subacute public hospital sector. SRT scores significantly discriminated between faller groups (Wilk's λ = 0.89, p = 0.05), with SRT score being the dominating predictor between groups. A receiver operating characteristic (ROC) curve showed good diagnostic accuracy with the area under curve = 0.78. A cutoff score of 394.5 ms provided the best balance between sensitivity and specificity. Once data were dichotomized as being above or below this cutoff value, a binary regression analysis revealed an odds ratio of 7.18 (95% CI 3.3-15.6), with a positive predictive value of 84.5%. The clinically feasible lower limb SRT testing protocol described provided good discrimination between single and multiple fallers. This test may be useful in clinical practice to help identify older people at greater risk of future falls.

The effects of apomorphine on visual perception in patients with Parkinson disease and visual hallucinations: a pilot study

Visual hallucinations (VHs) often occur in patients with advanced Parkinson disease (PD). Overstimulation of dopamine receptors has been considered as one of the causes for VHs in PD. However, several clinical studies suggested that apomorphine infusion did not worsen existing VHs in PD, but could even improve VHs in some PD patients. This pilot study included 4 PD patients with VHs, who were examined before, during, and after an intravenous infusion with apomorphine. The examinations included tests for lower- and higher-order visual functions, attention, and motor functions. Apomorphine had a significantly positive effect on contrast sensitivity and showed a significantly negative effect on attention. These results may explain why apomorphine is able to improve VHs in PD in some patients with mainly visual perceptive problems, but may also worsen VHs in other patients because of impaired attention.

Saccadic latency distributions in Parkinson's disease and the effects of L-dopa

Parkinson's disease (PD) is associated with a loss of central dopaminergic pathways in the brain leading to an abnormality of movement, including saccades. In PD, analysis of saccadic latency distributions, rather than mean latencies, can provide much more information about how the neural decision process that precedes movement is affected by disease or medication. Subject to the constraints of intersubject variation and reproducibility, latency distribution may represent an attractive potential biomarker of PD. Here we report two studies that provide information about these parameters, and demonstrate a novel effect of dopamine on saccadic latency, implying that it influences the neural decision process itself. We performed a detailed cross-sectional study of saccadic latency distributions during a simple step task in 22 medicated patients and 27 age-matched controls. This revealed high intersubject variability and an overlap of PD and control distributions. A second study was undertaken on a different population specifically to investigate the effects of dopamine on saccadic latency distributions in 15 PD patients. L-dopa was found to prolong latency, although the magnitude of the effect varied between subjects. The implications of these observations for the use of saccadic latency distributions as a potential biomarker of PD are discussed, as are the effects of L-dopa on neural decision making, where it is postulated to increase the criterion level of evidence required before the decision to move is made.

Gender related effects of heroin abuse on the simple reaction time task

Accumulated studies have demonstrated that there are serious negative consequences of drug abuse, especially the impairment of central nervous system (CNS) function. The simple reaction time (SRT) is the simplest model of measuring the function of the CNS. The purpose of the present study is to examine whether the SRT is affected by heroin abuse and whether such drug effect, if exists, is gender related. We found significant slowing of the SRT in both male and female heroin dependent patients at 1-3 months from withdrawal. However, the SRT slowing remitted after 3 months of abstinence in heroin dependent males but not in females. Our results suggested that the SRT is slowed by heroin abuse and such slowing is gender related.