Force overflow and levodopa-induced dyskinesias in Parkinson's disease

Force control of pinch grip: Normative data of a holistic evaluation

BACKGROUND

Pulp pinch (PP) is a vital hand movement involving muscle strength and sensory integration. Previous research has primarily focused on Maximal Voluntary Contraction, but PP encompasses broader parameters.

PURPOSE

This study aims to establish normative data for a comprehensive evaluation of thumb and index force control during PP, including endurance, precision, accuracy in unilateral PP, and force coordination in bilateral PP.

STUDY DESIGN

A cross-sectional study.

METHODS

Three hundred and twenty eight healthy Italian cis-gender participants (169 females, 159 males) were enrolled in a multiparametric force control evaluation of pinch grip, consisting in: sustained contraction (SC: ability to maintain a stable contraction at 40% MVC, measured as the time until exhaustion), dynamic contraction (DC: the ability to modulate precisely and accurately force output to follow a dynamic force trace), bimanual strength coordination (BSC: the ability to coordinate in-phase bimanual forces at different combined magnitudes) tasks. The sample was divided per sex and stratified in five age groups taking into account hand dominance. Differences in tasks' results between age, sex and hand-dominance were analysed.

RESULTS

Endurance (SC) was similar between younger and older adults (η2 =0.047 (Females) and η2 < 0.007 (Males)). Older adults exhibited lower precision (DC) and coordination (BSC) compared to young adults in both sexes (η2 >0.16). Females demonstrated greater endurance (SC) but lower precision and coordination (BSC) compared to males (0.01 <η2 <0.1). No hand dominance effect emerged in SC and DC.

CONCLUSIONS

Force accuracy and precision to modulate pinch force to perform a visual feedback force-matching task (DC) and force coordination between hands (BSC) worsen at increasing age. Hand dominance did not influence either endurance or precision of pinch grip in visual-feedback guided task.

Levodopa Dose Equivalency in Parkinson's Disease: Updated Systematic Review and Proposals

BACKGROUND

To compare drug regimens across clinical trials in Parkinson's disease (PD) conversion formulae between antiparkinsonian drugs have been developed. These are reported in relation to levodopa as the benchmark drug in PD pharmacotherapy as 'levodopa equivalent dose' (LED). Currently, the LED conversion formulae proposed in 2010 by Tomlinson et al. based on a systematic review are predominantly used. However, new drugs with established and novel mechanisms of action and novel formulations of longstanding drugs have been developed since 2010. Therefore, consensus proposals for updated LED conversion formulae are needed.

OBJECTIVES

To update LED conversion formulae based on a systematic review.

METHODS

The MEDLINE, CENTRAL, and Embase databases were searched from January 2010 to July 2021. Additionally, in a standardized process according to the GRADE grid method, consensus proposals were issued for drugs with scarce data on levodopa dose equivalency.

RESULTS

The systematic database search yielded 3076 articles of which 682 were eligible for inclusion in the systematic review. Based on these data and the standardized consensus process, we present proposals for LED conversion formulae for a wide range of drugs that are currently available for the pharmacotherapy of PD or are expected to be introduced soon.

CONCLUSIONS

The LED conversion formulae issued in this Position Paper will serve as a research tool to compare the equivalence of antiparkinsonian medication across PD study cohorts and facilitate research on the clinical efficacy of pharmacological and surgical treatments as well as other non-pharmacological interventions in PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Nanomedicine in the Face of Parkinson's Disease: From Drug Delivery Systems to Nanozymes

The complexity and overall burden of Parkinson's disease (PD) require new pharmacological approaches to counteract the symptomatology while reducing the progressive neurodegeneration of affected dopaminergic neurons. Since the pathophysiological signature of PD is characterized by the loss of physiological levels of dopamine (DA) and the misfolding and aggregation of the alpha-synuclein (α-syn) protein, new proposals seek to restore the lost DA and inhibit the progressive damage derived from pathological α-syn and its impact in terms of oxidative stress. In this line, nanomedicine (the medical application of nanotechnology) has achieved significant advances in the development of nanocarriers capable of transporting and delivering basal state DA in a controlled manner in the tissues of interest, as well as highly selective catalytic nanostructures with enzyme-like properties for the elimination of reactive oxygen species (responsible for oxidative stress) and the proteolysis of misfolded proteins. Although some of these proposals remain in their early stages, the deepening of our knowledge concerning the pathological processes of PD and the advances in nanomedicine could endow for the development of potential treatments for this still incurable condition. Therefore, in this paper, we offer: (i) a brief summary of the most recent findings concerning the physiology of motor regulation and (ii) the molecular neuropathological processes associated with PD, together with (iii) a recapitulation of the current progress in controlled DA release by nanocarriers and (iv) the design of nanozymes, catalytic nanostructures with oxidoreductase-, chaperon, and protease-like properties. Finally, we conclude by describing the prospects and knowledge gaps to overcome and consider as research into nanotherapies for PD continues, especially when clinical translations take place.

Cross-frequency phase-amplitude coupling in repetitive movements in patients with Parkinson's disease

Bradykinesia is a cardinal motor symptom in Parkinson’s disease (PD), the pathophysiology of which is not fully understood. We analyzed the role of cross-frequency coupling of oscillatory cortical activity in motor impairment in patients with PD and healthy controls. High-density EEG signals were recorded during various motor activities and at rest. Patients performed a repetitive finger-pressing task normally, but were slower than controls during tapping. Phase-amplitude coupling (PAC) between β (13–30 Hz) and broadband γ (50–150 Hz) was computed from individual EEG source signals in the premotor, primary motor, and primary somatosensory cortices, and the primary somatosensory complex. In all four regions, averaging the entire movement period resulted in higher PAC in patients than in controls for the resting condition and the pressing task (similar performance between groups). However, this was not the case for the tapping tasks where patients performed slower. This suggests the strength of state-related β-γ PAC does not determine Parkinsonian bradykinesia. Examination of the dynamics of oscillatory EEG signals during motor transitions revealed a distinctive motif of PAC rise and decay around press onset. This pattern was also present at press offset and slow tapping onset, linking such idiosyncratic PAC changes to transitions between different movement states. The transition-related PAC modulation in patients was similar to controls in the pressing task but flattened during slow tapping, which related to normal and abnormal performance, respectively. These findings suggest that the dysfunctional evolution of neuronal population dynamics during movement execution is an important component of the pathophysiology of Parkinsonian bradykinesia.

NEW & NOTEWORTHY Our findings using noninvasive EEG recordings provide evidence that PAC dynamics might play a role in the physiological cortical control of movement execution and may encode transitions between movement states. Results in patients with Parkinson’s disease suggest that bradykinesia is related to a deficit of the dynamic regulation of PAC during movement execution rather than its absolute strength. Our findings may contribute to the development of a new concept of the pathophysiology of bradykinesia.

Cognitive outcome following bilateral subthalamic nucleus deep brain stimulation for Parkinson's disease-a comparative observational study in Indian patients

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor symptoms and motor complications of Parkinson's disease (PD). The intervention is expected to result in some cognitive changes, the nature of which is not uniform across the studies which have reported them. PD itself is associated with progressive cognitive decline and hence longitudinal follow-up studies with medically managed control group of patients are needed to explore the cognitive deficits attributable to DBS.

METHODS

We conducted a prospective comparative observational study to assess the effects of bilateral STN DBS on cognition. Cognitive functions were assessed at baseline and after a minimum of two years after surgery, and compared with baseline and follow-up assessments in patients on medical management alone.

RESULTS

Thirty-four patients with PD who underwent bilateral STN DBS and thirty-four medically managed patients participated in the study. At a mean follow-up of around 33 months, we found a significant decline in verbal fluency scores in the DBS group compared to those on medical management alone (1.15 ± 1.23 vs 0.59 ± 0.93, p = 0.034) and a trend for decline was noted in digit span test. There was no difference in the performance in tests addressing other cognitive domains, or tests of global cognitive function. No patient developed dementia. Motor functions and activities of daily living (ADL) were significantly better in the surgical group.

CONCLUSION

STN DBS results in minor deficits in executive functions, particularly verbal fluency. These may be inconsequential, considering the marked improvement in motor functions and ADL.

Asleep deep brain stimulation with intraoperative magnetic resonance guidance: a single-institution experience

OBJECTIVE

Deep brain stimulation (DBS) is traditionally performed on an awake patient with intraoperative recordings and test stimulation. DBS performed under general anesthesia with intraoperative MRI (iMRI) has demonstrated high target accuracy, reduced operative time, direct confirmation of target placement, and the ability to place electrodes without cessation of medications. The authors describe their initial experience with using iMRI to perform asleep DBS and discuss the procedural and radiological outcomes of this procedure.

METHODS

All DBS electrodes were implanted under general anesthesia by a single surgeon by using a neuronavigation system with 3-T iMRI guidance. Clinical outcomes, operative duration, complications, and accuracy were retrospectively analyzed.

RESULTS

In total, 103 patients treated from 2015 to 2019 were included, and all but 1 patient underwent bilateral implantation. Indications included Parkinson's disease (PD) (65% of patients), essential tremor (ET) (29%), dystonia (5%), and refractory epilepsy (1%). Targets included the globus pallidus pars internus (12.62% of patients), subthalamic nucleus (56.31%), ventral intermedius nucleus of the thalamus (30%), and anterior nucleus of the thalamus (1%). Technically accurate lead placement (radial error ≤ 1 mm) was obtained for 98% of leads, with a mean (95% CI) radial error of 0.50 (0.46-0.54) mm; all leads were placed with a single pass. Predicted radial error was an excellent predictor of real radial error, underestimating real error by only a mean (95% CI) of 0.16 (0.12-0.20) mm. Accuracy remained high irrespective of surgeon experience, but procedure time decreased significantly with increasing institutional and surgeon experience (p = 0.007), with a mean procedure duration of 3.65 hours. Complications included 1 case of intracranial hemorrhage (asymptomatic) and 1 case of venous infarction (symptomatic), and 2 patients had infection at the internal pulse generator site. The mean ± SD voltage was 2.92 ± 0.83 V bilaterally at 1-year follow-up. Analysis of long-term clinical efficacy demonstrated consistent postoperative improvement in clinical symptoms, as well as decreased drug doses across all indications and follow-up time points, including mean decrease in levodopa-equivalent daily dose by 53.57% (p < 0.0001) in PD patients and mean decrease in primidone dose by 61.33% (p < 0.032) in ET patients at 1-year follow-up.

CONCLUSIONS

A total of 205 leads were placed in 103 patients by a single surgeon under iMRI guidance with few operative complications. Operative time trended downward with increasing institutional experience, and technical accuracy of radiographic lead placement was consistently high. Asleep DBS implantation with iMRI appears to be a safe and effective alternative to standard awake procedures.

Cerebrospinal fluid cytokines in multiple system atrophy: A cross-sectional Catalan MSA registry study

INTRODUCTION

Neuroinflammation is a potential player in neurodegenerative conditions, particularly the aggressive ones, such as multiple system atrophy (MSA). Previous reports on cytokine levels in MSA using serum or cerebrospinal fluid (CSF) have been inconsistent, including small samples and a limited number of cytokines, often without comparison to Parkinson's disease (PD), a main MSA differential diagnosis.

METHODS

Cross-sectional study of CSF levels of 38 cytokines using a multiplex assay in 73 participants: 39 MSA patients (19 with parkinsonian type [MSAp], 20 with cerebellar type [MSAc]; 31 probable, 8 possible), 19 PD patients and 15 neurologically unimpaired controls. None of the participants was under non-steroidal anti-inflammatory drugs at the time of the lumbar puncture.

RESULTS

There were not significant differences in sex and age among participants. In global non-parametric comparisons FDR-corrected for multiple comparisons, CSF levels of 5 cytokines (FGF-2, IL-10, MCP-3, IL-12p40, MDC) differed among the three groups. In pair-wise FDR-corrected non-parametric comparisons 12 cytokines (FGF-2, eotaxin, fractalkine, IFN-α2, IL-10, MCP-3, IL-12p40, MDC, IL-17, IL-7, MIP-1β, TNF-α) were significantly higher in MSA vs. non-MSA cases (PD + controls pooled together). Of these, MCP-3 and MDC were the most significant ones, also differed in MSA vs. PD, and were significant MSA-predictors in binary logistic regression models and ROC curves adjusted for age. CSF levels of fractalkine and MIP-1α showed a strong and significant positive correlation with UMSARS-2 scores.

CONCLUSION

Increased CSF levels of cytokines such as MCP-3, MDC, fractalkine and MIP-1α deserve consideration as potential diagnostic or severity biomarkers of MSA.

Remnants of Cardinal Symptoms of Parkinson's Disease, Not Dyskinesia, Are Problematic for Dyskinetic Patients Performing Activities of Daily Living

Introduction: The impact of levodopa-induced dyskinesia (LID) on the daily lives of patients with Parkinson's disease (PD) remains to be determined. Furthermore, evidence suggests that cardinal motor symptoms of PD may coexist with LID, but their impact on activities of daily living (ADL) relative to LID is not known. This cross-sectional study aimed at determining the effect of LID and cardinal motor symptoms of PD on ADL in patients who were experiencing peak-dose choreic-type LID.

Method: One hundred and twenty-one patients diagnosed with PD known to experience choreic-type LID were recruited for the study. Patients were asked to perform a set of ADL. Levels of LID, tremor, bradykinesia, and freezing of gait (FoG) were measured using 17 inertial sensors design to capture full body movements, while rigidity, and postural instability were assessed using clinical evaluations. Cognition was also assessed using the mini-mental state examination. Success criteria were set for each ADL using the time needed to perform the task and errors measured in 69 age-gender-matched healthy controls. Binary logistic regressions were used to identify symptoms influencing success or failure for each activity. Receiver operating characteristic curves were computed on each significant symptom, and Youden indexes were calculated to determine the critical level of symptomatology at which the performance significantly changed.

Results: Results show that 97.7% of patients who presented with LID during the experiment also presented with at least one cardinal motor symptom. On average, patients took more time and did more errors during ADL. Multivariate analyses revealed that for the great majority of ADL, LID were not associated with worsening of performance; however, postural instability, tremor, rigidity, and cognitive decline significantly decreased the odds of success.

Conclusions: Residual symptoms of PD, such as tremor, rigidity, and postural instability still present at peak-dose were more problematic than LID in the performance of ADL for patients experiencing slight-to-moderate LID. We also found that cognitive decline was associated with decreased performance in certain tasks. Therefore, a strategy using lower doses of medication to manage LID may be counterproductive since it would not address most of these symptoms already present in patients.

Pallidal Deep-Brain Stimulation Disrupts Pallidal Beta Oscillations and Coherence with Primary Motor Cortex in Parkinson's Disease

In Parkinson's disease (PD), subthalamic nucleus beta band oscillations are decreased by therapeutic deep-brain stimulation (DBS) and this has been proposed as important to the mechanism of therapy. The globus pallidus is a common alternative target for PD with similar motor benefits as subthalamic DBS, but effects of pallidal stimulation in PD are not well studied, and effects of pallidal DBS on cortical function in PD are unknown. Here, in 20 PD and 14 isolated dystonia human patients of both genders undergoing pallidal DBS lead implantation, we recorded local field potentials from the globus pallidus and in a subset of these, recorded simultaneous sensorimotor cortex ECoG potentials. PD patients had elevated resting pallidal low beta band (13-20 Hz) power compared with dystonia patients, whereas dystonia patients had elevated resting pallidal theta band (4-8 Hz) power compared with PD. We show that this results in disease-specific patterns of interaction between the pallidum and motor cortex: PD patients demonstrated relatively elevated phase coherence with the motor cortex in the beta band and this was reduced by therapeutic pallidal DBS. Dystonia patients had greater theta band phase coherence. Our results support the hypothesis that specific motor phenomenology observed in movement disorders are associated with elevated network oscillations in specific frequency bands, and that DBS in movement disorders acts in general by disrupting elevated synchronization between basal ganglia output and motor cortex.SIGNIFICANCE STATEMENT Perturbations in synchronized oscillatory activity in brain networks are increasingly recognized as important features in movement disorders. The globus pallidus is a commonly used target for deep-brain stimulation (DBS) in Parkinson's disease (PD), however, the effects of pallidal DBS on basal ganglia and cortical oscillations are unknown. Using invasive intraoperative recordings in patients with PD and isolated dystonia, we found disease-specific patterns of elevated oscillatory synchronization within the pallidum and in coherence between pallidum and motor cortex. Therapeutic pallidal DBS in PD suppresses these elevated synchronizations, reducing the influence of diseased basal ganglia on cortical physiology. We propose a general mechanism for DBS therapy in movement disorders: functional disconnection of basal ganglia output and motor cortex by coherence suppression.

Cerebrospinal fluid levels of coenzyme Q10 are reduced in multiple system atrophy

INTRODUCTION

The finding of mutations of the COQ2 gene and reduced coenzyme Q10 levels in the cerebellum in multiple system atrophy (MSA) suggest that coenzyme Q10 is relevant to MSA pathophysiology. Two recent studies have reported reduced coenzyme Q10 levels in plasma and serum (respectively) of MSA patients compared to Parkinson's disease and/or control subjects, but with largely overlapping values, limited comparison with other parkinsonisms, or dependence on cholesterol levels. We hypothesized that cerebrospinal fluid (CSF) is reliable to assess reductions in coenzyme Q10 as a candidate biomarker of MSA.

METHODS

In this preliminary cross-sectional study we assessed CSF coenzyme Q10 levels in 20 patients with MSA from the multicenter Catalan MSA Registry and of 15 PD patients, 10 patients with progressive supranuclear palsy (PSP), and 15 control subjects from the Movement Disorders Unit Biosample Collection of Hospital Clinic de Barcelona. A specific ELISA kit was used to determine CSF coenzyme Q10 levels. CSF coenzyme Q10 levels were compared in MSA vs. the other groups globally, pair-wise, and by binary logistic regression models adjusted for age, sex, disease severity, disease duration, and dopaminergic treatment.

RESULTS

CSF coenzyme Q10 levels were significantly lower in MSA than in other groups in global and pair-wise comparisons, as well as in multivariate regression models. Receiver operating characteristic curve analyses yielded significant areas under the curve for MSA vs. PD, PSP and controls.

CONCLUSIONS

These findings support coenzyme Q10 relevance in MSA. Low CSF coenzyme Q10 levels deserve further consideration as a biomarker of MSA.

Cross-sectional and longitudinal associations of motor fluctuations and non-motor predominance with cerebrospinal τ and Aβ as well as dementia-risk in Parkinson's disease

Experimental, neuropathological and cerebrospinal fluid (CSF) studies support τ and amyloid-β (Aβ) relevance in Parkinson's disease (PD) related dementia. Lesser motor fluctuations (MFs) and non-motor features have also been related to PD-dementia. Yet, little is known about the association of MFs and non-motor symptoms with CSF τ and Aβ in PD. We hypothesized that lesser MFs and non-motor predominance are related to these CSF markers and dementia-risk in PD. We studied 58 PD patients (dementia at baseline, n=21; dementia at 18-months, n=35) in whom CSF Aβ and τ had been determined with ELISA techniques. MFs and a number of non-motor symptoms (apathy, anxiety, irritability, depression, visual hallucinations, spatial disorientation, memory complaints) over disease course were dichotomized as absent-mild vs. moderate-severe by retrospective clinical chart review blind to CSF findings. Non-motor predominance was defined as ≥3 non-motor symptoms (after the cohort-median of non-motor symptoms per patient) with ≥2 being moderate-severe and ≥1 having been present from onset, with all these being more disabling overall than motor features. Cross-sectionally, CSF biomarkers were non-parametrically compared according to dichotomized MFs and non-motor predominance. Longitudinally, dementia was the outcome (dependent variable), CSF markers, MFs and non-motor predominance were the predictors (independent variables), and potential modifiers as age, sex, and memory complaints were the covariates in binary regression models. Absent-mild MFs were associated with higher CSF τ markers and shorter time-to-dementia, while non-motor predominance and decreasing CSF Aβ independently increased longitudinal dementia-risk. In summary, absent-mild MFs, non-motor predominance and CSF τ and Aβ might define endophenotypes related to the timing or risk of dementia in PD.

Specific Attentional Disorders and Freezing of Gait in Parkinson's Disease

BACKGROUND

Due to its high prevalence in dual-task paradigms, freezing of gait in Parkinson's disease is thought to be associated with dysexecutive syndrome and attentional disorders. However, the role of specific attentional disorders in patients with freezing of gait is still unclear.

OBJECTIVE

Here, we sought to specifically determine which basic attentional modalities are impaired in patients with freezing of gait.

METHODS

Seventy-eight parkinsonian patients performed a computer-controlled reaction-time paradigm designed to measure the different attentional subcomponents, controlled for visuospatial processing and motor participation.

RESULTS

The freezer (n = 42) and non-freezer (n = 36) groups were matched for age, educational level, MMSE and Mattis Dementia Rating Scale. There were no intergroup differences in simple reaction times, whereas choice reaction times were higher in the freezer group than in the non-freezer group for divided attention (p = 0.023).

CONCLUSIONS

At equivalent levels of overall cognitive efficiency, freezer patients showed a greater slowdown than non-freezer patients with a specific impairment in divided attention.

Clinical management of patients with advanced Parkinson's disease treated with continuous intestinal infusion of levodopa/carbidopa

Patients with Parkinson's disease often have a good initial response to dopaminergic therapy but later usually develop motor fluctuations and dyskinesia. In these patients, continuous infusion of levodopa-carbidopa intestinal gel (LCIG) allows for maintaining adequate dopamine levels and for improving motor and nonmotor symptoms, as well as quality of life and autonomy. Adequate candidate selection and follow-up are crucial for treatment success. Management should be multidisciplinary, and patient and caregiver education is a priority. This expert consensus document has been developed by a team of neurologists, gastroenterologists and nurses who have a vast experience in LCIG therapy, with an intention to provide knowledge and tools to facilitate patient management throughout all phases of LCIG treatment process.

Clinical outcomes using ClearPoint interventional MRI for deep brain stimulation lead placement in Parkinson’s disease

OBJECT

The ClearPoint real-time interventional MRI-guided methodology for deep brain stimulation (DBS) lead placement may offer advantages to frame-based approaches and allow accurate implantation under general anesthesia. In this study, the authors assessed the safety and efficacy of DBS in Parkinson’s disease (PD) using this surgical method.

METHODS

This was a prospective single-center study of bilateral DBS therapy in patients with advanced PD and motor fluctuations. Symptom severity was evaluated at baseline and 12 months postimplantation using the change in Unified Parkinson’s Disease Rating Scale (UPDRS) Part III “off” medication score as the primary outcome variable.

RESULTS

Twenty-six PD patients (15 men and 11 women) were enrolled from 2010 to 2013. Twenty patients were followed for 12 months (16 with a subthalamic nucleus target and 4 with an internal globus pallidus target). The mean UPDRS Part III “off” medication score improved from 40.75 ± 10.9 to 24.35 ± 8.8 (p = 0.001). “On” medication time without troublesome dyskinesia increased 5.2 ± 2.6 hours per day (p = 0.0002). UPDRS Parts II and IV, total UPDRS score, and dyskinesia rating scale “on” medication scores also significantly improved (p < 0.01). The mean levodopa equivalent daily dose decreased from 1072.5 ± 392 mg to 828.25 ± 492 mg (p = 0.046). No significant cognitive or mood declines were observed. A single brain penetration was used for placement of all leads, and the mean targeting error was 0.6 ± 0.3 mm. There were 3 serious adverse events (1 DBS hardware-related infection, 1 lead fracture, and 1 unrelated death).

CONCLUSIONS

DBS leads placed using the ClearPoint interventional real-time MRI-guided method resulted in highly accurate lead placement and outcomes comparable to those seen with frame-based approaches.

Cortical and motor responses to acute forced exercise in Parkinson's disease

INTRODUCTION

Studies in animal models of Parkinson's disease (PD) have suggested that the rate of exercise performance is important in treatment efficacy and neuroprotection. In humans with PD, lower-extremity forced-exercise (FE) produced global improvements in motor symptoms based on clinical ratings and biomechanical measures of upper extremity function.

METHODS

fMRI was used to compare the underlying changes in brain activity in PD patients following the administration of anti-parkinsonian medication and following a session of FE.

RESULTS

Nine individuals with PD completed fMRI scans under each condition: off anti-PD medication, on anti-PD medication, and off medication + FE. Unified Parkinson's Disease Rating Motor Scale scores improved by 50% in the FE condition compared to the off-medication condition. The pattern of fMRI activation after FE was similar to that seen with anti-PD medication. Direct comparison of the fMRI activation patterns showed high correlation between FE and anti-PD medication.

CONCLUSION

These findings suggest that medication and FE likely utilize the same pathways to produce symptomatic relief in individuals with PD.

Reduced plasma taurine level in Parkinson's disease: association with motor severity and levodopa treatment

PURPOSE

This study aimed to evaluate the level of taurine in plasma, and its association with the severity of motor and non-motor symptoms (NMS) and chronic levodopa treatment in Parkinson's disease (PD).

PATIENTS AND METHODS

Plasma taurine level was measured in treated PD (tPD), untreated PD (ntPD) and control groups. Motor symptoms and NMS were assessed using the Unified Parkinson's Disease Rating Scale, the short form of the McGill Pain Questionnaire, the Hamilton Depression Scale, the Scale for Outcomes in Parkinson's disease for Autonomic Symptoms and the Pittsburgh Sleep Quality Index. Longtime exposure to levodopa was indicated by its approximate cumulative dosage.

RESULTS

The plasma taurine levels of PD patients were decreased when compared with controls and negatively associated with motor severity but not NMS. Moreover, tPD patients exhibited lower levels of plasma taurine than ntPD patients. Interestingly, plasma taurine levels negatively correlated with cumulative levodopa dosage in tPD. After controlling for potential confounders, the association between taurine and levodopa remained significant.

CONCLUSION

Our study supports that taurine may play important roles in the pathophysiology of PD and the disturbances caused by chronic levodopa administration.

The association between clinically relevant anxiety and other non-motor symptoms in Parkinson's disease

Anxiety disorders in patients with Parkinson's disease (PD) are often missed due to an overlap with other non-motor symptoms. The relationships between anxiety and other non-motor symptoms in PD still remain unclear. We used the Hamilton anxiety rating scale and the Non-motor Symptoms Questionnaire to measure anxiety and the complex range of non-motor symptoms in 99 PD patients. The relationships between anxiety and other PD-related non-motor symptoms were examined through regression analyses. 25 % of PD patients were diagnosed with clinically relevant anxiety. Non-motor symptoms were more prominent in patients with anxiety. Depression, urinary disorders, and sleep disruption were the factors most likely to influence anxiety in PD. Our findings have revealed a strong interplay between anxiety and other non-motor symptoms of PD and have highlighted the need for a holistic approach towards the clinical treatment of this disabling condition.

Factors contributing to caregivers' stress and burden in Parkinson's disease

BACKGROUND AND OBJECTIVE

To analyze the main determinants of burden and stress in caregivers of Spanish Parkinson's disease (PD) patients.

METHODS

One-hundred and twenty-one non-demented patients with PD (57.9% males; 70.9 ± 8.2 years old) were included in this cross-sectional, monocenter, evaluation study. Caregivers (n = 121; 71.9% females; 60.2 ± 15 years old) were assessed using the Zarit Caregiver Burden Inventory (ZCBI) and Caregiver Strain Index (CSI). Multiple linear regression methods were used to evaluate factors contributing to caregivers' stress and burden: (i) PD motor dysfunction (ON-state Hoehn & Yahr/Unified Parkinson's Disease Rating Scale [UPDRS] part III and motor complications [UPDRS part IV]); (ii) Mood (Beck Depression Inventory [BDI]); (iii) Non-motor symptoms (Non-Motor Symptoms Scale [NMSS]); (iv) Disability (Schwab & England Activities of Daily Living Scale [ADLS]); and (v) Socio-demographic and other disease-related variables.

RESULTS

Zarit Caregiver Burden Inventory and CSI mean scores were 16 ± 13.9 and 2.1 ± 2.3, respectively. High correlation was found between ZCBI and CSI (r = 0.819; P < 0.0001). Moderate to severe burden (ZCBI > 40) was present in 9.1% of caregivers; 5.8% had high levels of stress (CSI ≥ 7). Moderate to strong correlations were observed between patient-related variables (Hoehn&Yahr, UPDRS-III, UPDRS-IV, BDI, NMSS, and ADLS) and ZCBI and CSI (P < 0.0001). Linear regression methods showed that ADLS had the strongest influence on ZCBI and CSI, followed by BDI on ZCBI.

CONCLUSIONS

Disability (ADLS) and mood (BDI) of patients with PD are the main factors contributing to burden and stress in caregivers.

Greater striatal responses to medication in Parkinson׳s disease are associated with better task-switching but worse reward performance

Dopaminergic medication in Parkinson's disease has been proposed to improve cognitive processing by modulating the severely depleted dorsal striatum, while impairing reward processing by modulating the relatively intact ventral striatum. However, there is no direct (neural) evidence for this hypothesis. Here we fill this gap by scanning Parkinson's disease patients (n=15) ON and relatively OFF their dopaminergic medication using functional magnetic resonance imaging. During scanning, patients performed a task that enabled the simultaneous measurement of task-switching and reward-related processing. Brain-behavior correlations revealed that medication-related increases (ON-OFF) in switch-related BOLD signal (switch-repeat) in the dorsomedial striatum were associated, on an individual basis, with improvements in task-switching (i.e. a decreased switch cost). Conversely, medication-related increases (ON-OFF) in reward-related BOLD signal (high-low) in the ventromedial striatum were associated, on an individual basis, with impairments in performance in anticipation of reward (i.e. an increased reward cost). Linear regression analyses demonstrated that the positive relationship between medication-related changes in BOLD and the reward cost was unique to the ventromedial striatum, whereas the negative relationship between medication-related changes in BOLD and the switch cost was not unique to the dorsomedial striatum. These findings extend the dopamine overdose hypothesis, according to which dopamine-induced changes in dorsal and ventral striatal processing lead to cognitive improvement and impairment respectively.

Excessive Sensitivity to Uncertain Visual Input in L-DOPA-Induced Dyskinesias in Parkinson's Disease: Further Implications for Cerebellar Involvement

When faced with visual uncertainty during motor performance, humans rely more on predictive forward models and proprioception and attribute lesser importance to the ambiguous visual feedback. Though disrupted predictive control is typical of patients with cerebellar disease, sensorimotor deficits associated with the involuntary and often unconscious nature of l-DOPA-induced dyskinesias in Parkinson’s disease (PD) suggests dyskinetic subjects may also demonstrate impaired predictive motor control.

Methods: We investigated the motor performance of 9 dyskinetic and 10 non-dyskinetic PD subjects on and off l-DOPA, and of 10 age-matched control subjects, during a large-amplitude, overlearned, visually guided tracking task. Ambiguous visual feedback was introduced by adding “jitter” to a moving target that followed a Lissajous pattern. Root mean square (RMS) tracking error was calculated, and ANOVA, robust multivariate linear regression, and linear dynamical system analyses were used to determine the contribution of speed and ambiguity to tracking performance.

Results: Increasing target ambiguity and speed contributed significantly more to the RMS error of dyskinetic subjects off medication. l-DOPA improved the RMS tracking performance of both PD groups. At higher speeds, controls and PDs without dyskinesia were able to effectively de-weight ambiguous visual information.

Conclusion: PDs’ visually guided motor performance degrades with visual jitter and speed of movement to a greater degree compared to age-matched controls. However, there are fundamental differences in PDs with and without dyskinesia: subjects without dyskinesia are generally slow, and less responsive to dynamic changes in motor task requirements, but in PDs with dyskinesia, there was a trade-off between overall performance and inappropriate reliance on ambiguous visual feedback. This is likely associated with functional changes in posterior parietal–ponto–cerebellar pathways.

Predictors of cognitive impairment in an early stage Parkinson's disease cohort

The impact of Parkinson’s disease (PD) dementia is substantial and has major functional and socioeconomic consequences. Early prediction of future cognitive impairment would help target future interventions. The Montreal Cognitive Assessment (MoCA), the Mini-Mental State Examination (MMSE), and fluency tests were administered to 486 patients with PD within 3.5 years of diagnosis, and the results were compared with those from 141 controls correcting for age, sex, and educational years. Eighteen-month longitudinal assessments were performed in 155 patients with PD. The proportion of patients classified with normal cognition, mild cognitive impairment (MCI), and dementia varied considerably, depending on the MoCA and MMSE thresholds used. With the MoCA total score at screening threshold, 47.7%, 40.5%, and 11.7% of patients with PD were classified with normal cognition, MCI, and dementia, respectively; by comparison, 78.7% and 21.3% of controls had normal cognition and MCI, respectively. Cognitive impairment was predicted by lower education, increased age, male sex, and quantitative motor and non-motor (smell, depression, and anxiety) measures. Longitudinal data from 155 patients with PD over 18 months showed significant reductions in MoCA scores, but not in MMSE scores, with 21.3% of patients moving from normal cognition to MCI and 4.5% moving from MCI to dementia, although 13.5% moved from MCI to normal; however, none of the patients with dementia changed their classification. The MoCA may be more sensitive than the MMSE in detecting early baseline and longitudinal cognitive impairment in PD, because it identified 25.8% of those who experienced significant cognitive decline over 18 months. Cognitive decline was associated with worse motor and non-motor features, suggesting that this reflects a faster progressive phenotype.

Subthalamic nucleus neurons are synchronized to primary motor cortex local field potentials in Parkinson's disease

In Parkinson's disease (PD), striatal dopamine denervation results in a cascade of abnormalities in the single-unit activity of downstream basal ganglia nuclei that include increased firing rate, altered firing patterns, and increased oscillatory activity. However, the effects of these abnormalities on cortical function are poorly understood. Here, in humans undergoing deep brain stimulator implantation surgery, we use the novel technique of subdural electrocorticography in combination with subthalamic nucleus (STN) single-unit recording to study basal ganglia-cortex interactions at the millisecond time scale. We show that in patients with PD, STN spiking is synchronized with primary motor cortex (M1) local field potentials in two distinct patterns: first, STN spikes are phase-synchronized with M1 rhythms in the theta, alpha, or beta (4-30 Hz) bands. Second, STN spikes are synchronized with M1 gamma activity over a broad spectral range (50-200 Hz). The amplitude of STN spike-synchronized gamma activity in M1 is itself rhythmically modulated by the phase of a lower-frequency rhythm (phase-amplitude coupling), such that "waves" of phase-synchronized gamma activity precede the occurrence of STN spikes. We show the disease specificity of these phenomena in PD, by comparison with STN-M1 paired recordings performed in a group of patients with a different disorder, primary craniocervical dystonia. Our findings support a model of the basal ganglia-thalamocortical loop in PD in which gamma activity in primary motor cortex, modulated by the phase of low-frequency rhythms, drives STN unit discharge.

Decomposing effects of dopaminergic medication in Parkinson's disease on probabilistic action selection--learning or performance?

Dopamine has long been implicated in reward-based learning and the expression of such learned associations on performance. Robust evidence supports its effects on learning and performance, but teasing these apart has proved challenging. Here we have adapted a classic test of value-based learning, the probabilistic selection task, to disentangle effects of dopamine on value-based performance from effects on value-based learning. Valence-specific effects of dopamine on this specific task cannot be accounted for by modulation of learning, and therefore must reflect modulation of performance. We found that dopaminergic medication, consisting of levodopa and/or dopamine agonists taken at own dose, in 18 patients with mild Parkinson's disease (Hoehn and Yahr < 2.5) potentiated reward-based approach in terms of both accuracy and reaction times, while leaving punishment-based avoidance unaffected. These data demonstrate that the effects of dopamine on probabilistic action selection are at least partly mediated by effects on the expression of learned associations rather than on learning itself, and help refine current models of dopamine's role in reward.

Clinical outcomes of PD patients having bilateral STN DBS using high-field interventional MR-imaging for lead placement

OBJECTIVE

Recently, an iMRI-guided technique for implanting DBS electrodes without MER was developed at our center. Here we report the clinical outcomes of PD patients undergoing STN DBS surgery using this surgical approach.

METHODS

Consecutive PD patients undergoing bilateral STN DBS using this method were prospectively studied. Severity of PD was determined using the UPDRS scores, Hoehn and Yahr staging score, stand-sit-walk testing, and the dyskinesia rating scale. The primary outcome measure was the change in UPDRS III off medication score at 6 months. DBS stimulation parameters, adverse events, levodopa equivalent daily dose (LEDD), and DBS lead locations were also recorded. Seventeen advanced PD patients (9M/8F) were enrolled from 2007 to 2009.

RESULTS

The mean UPDRS III off medication score improved from 44.5 to 22.5 (49.4%) at 6 months (p=0.001). Other secondary outcome measures (UPDRS II, III on medication, and IV) significantly improved as well (p<0.01). LEDD decreased by an average of 24.7% (p=0.003). Average stimulation parameters were: 2.9V, 66.4μs, 154Hz.

CONCLUSION

This pilot study demonstrates that STN DBS leads placed using the iMRI-guided method results in significantly improved outcomes in PD symptoms, and these outcomes are similar to what has been reported using traditional frame-based, MER-guided stereotactic methods.

Sleep-related falling out of bed in Parkinson's disease

BACKGROUND AND PURPOSE

Sleep-related falling out of bed (SFOB), with its potential for significant injury, has not been a strong focus of investigation in Parkinson's disease (PD) to date. We describe the demographic and clinical characteristics of PD patients with and without SFOB.

METHODS

We performed a retrospective analysis of 50 consecutive PD patients, who completed an REM sleep behavior disorder screening questionnaire (RBDSQ), questionnaires to assess for RBD clinical mimickers and questions about SFOB and resulting injuries. Determination of high risk for RBD was based on an RBDSQ score of 5 or greater.

RESULTS

Thirteen patients reported history of SFOB (26%). Visual hallucinations, sleep-related injury, quetiapine and amantadine use were more common in those patients reporting SFOB. Twenty-two patients (44%) fulfilled criteria for high risk for RBD, 12 of which (55%) reported SFOB. Five patients reported injuries related to SFOB. SFOB patients had higher RBDSQ scores than non-SFOB patients (8.2±3.0 vs. 3.3±2.0, p<0.01). For every one unit increase in RBDSQ score, the likelihood of SFOB increased two-fold (OR 2.4, 95% CI 1.3-4.2, p<0.003).

CONCLUSIONS

SFOB may be a clinical marker of RBD in PD and should prompt confirmatory polysomnography and pharmacologic treatment to avoid imminent injury. Larger prospective studies are needed to identify risk factors for initial and recurrent SFOB in PD.

Oscillations in sensorimotor cortex in movement disorders: an electrocorticography study

Movement disorders of basal ganglia origin may arise from abnormalities in synchronized oscillatory activity in a network that includes the basal ganglia, thalamus and motor cortices. In humans, much has been learned from the study of basal ganglia local field potentials recorded from temporarily externalized deep brain stimulator electrodes. These studies have led to the theory that Parkinson's disease has characteristic alterations in the beta frequency band (13-30 Hz) in the basal ganglia-thalamocortical network. However, different disorders have rarely been compared using recordings in the same structure under the same behavioural conditions, limiting straightforward assessment of current hypotheses. To address this, we utilized subdural electrocorticography to study cortical oscillations in the three most common movement disorders: Parkinson's disease, primary dystonia and essential tremor. We recorded local field potentials from the arm area of primary motor and sensory cortices in 31 subjects using strip electrodes placed temporarily during routine surgery for deep brain stimulator placement. We show that: (i) primary motor cortex broadband gamma power is increased in Parkinson's disease compared with the other conditions, both at rest and during a movement task; (ii) primary motor cortex high beta (20-30 Hz) power is increased in Parkinson's disease during the 'stop' phase of a movement task; (iii) the alpha-beta peaks in the motor and sensory cortical power spectra occur at higher frequencies in Parkinson's disease than in the other two disorders; and (iv) patients with dystonia have impaired movement-related beta band desynchronization in primary motor and sensory cortices. The findings support the emerging hypothesis that disease states reflect abnormalities in synchronized oscillatory activity. This is the first study of sensorimotor cortex local field potentials in the three most common movement disorders.

Nonmotor versus motor symptoms: how much do they matter to health status in Parkinson's disease?

Evidence suggests that both motor and nonmotor symptoms contribute to health status in Parkinson's disease. Less clear is how much change in health status can be expected if these clinical variables change. In addition, anxiety, separate from depression, has rarely been examined as a predictor of health status. We used hierarchical multiple regression analysis and standardized beta coefficients in a prevalent cohort of 462 patients with Parkinson's disease to explore the relative impact on health status (measured using the Parkinson's Disease Questionnaire) of 5 well-recognized symptom domains in Parkinson's disease: motor signs, depression, anxiety, cognition, and other nonmotor symptoms. In the health status scores, 19.6% of variance was explained by age, number of comorbidities, disease duration, and levodopa equivalent dose. Younger age predicted worse health status. A full regression model containing baseline variables and all 5 symptom domains explained 56% of the variance in health status. The standardized beta coefficient for depression was 2.1, 1.6, and 1.3 times that of motor signs, anxiety, and other nonmotor symptoms, respectively. Our findings provide a ranking order of clinical variables for their relative impact on health status in Parkinson's disease and show that depression has more than twice the impact of motor signs on health status. Anxiety and other nonmotor symptoms are also important separate determinants of poor health status in Parkinson's disease. Our results will help to guide the development of individual care and service planning for patients with Parkinson's disease.

Motor imagery evokes increased somatosensory activity in Parkinson's disease patients with tremor

Parkinson's disease (PD) is surprisingly heterogeneous: some patients have a prominent resting tremor, while others never develop this symptom. Here we investigate whether the functional organization of the voluntary motor system differs between PD patients with and without resting tremor, and whether these differences relate to the cerebral circuit producing tremor. We compared 18 PD patients with marked tremor, 20 PD patients without tremor, and 19 healthy controls. Subjects performed a controlled motor imagery task during fMRI scanning. We quantified imagery-related cerebral activity by contrasting imagery of biomechanically difficult and easy movements. Tremor-related activity was identified by relating cerebral activity to fluctuations in tremor amplitude, using electromyography during scanning. PD patients with tremor had better behavioral performance than PD patients without tremor. Furthermore, tremulous PD patients showed increased imagery-related activity in somatosensory area 3a, as compared with both healthy controls and to nontremor PD patients. This effect was independent from tremor-related activity, which was localized to the motor cortex, cerebellum, and thalamic ventral intermediate nucleus (VIM). The VIM, with known projections to area 3a, was unique in showing both tremor- and imagery-related responses. We conclude that parkinsonian tremor influences motor imagery by modulating central somatosensory processing through the VIM. This mechanism may explain clinical differences between PD patients with and without tremor.

Dysfunctions of cerebral networks precede recognition memory deficits in early Parkinson's disease

We aimed to investigate changes in the verbal recognition memory network in patients with early Parkinson's disease (PD) without overt recognition memory alteration. Verbal recognition memory was assessed in 24 PD patients in early stages of the disease and a control group of 24 healthy subjects during fMRI data acquisition. Participants were presented with a list of 35 words before imaging, and later during fMRI scanning they were required to recognize these previously presented words. Both model-based (FEAT) and model-free (MELODIC) analyses of the fMRI data were carried out with FSL software. Memory was also assessed by means of Rey's Auditory Verbal Learning Test (RAVLT). PD patients showed no difference in the fMRI recognition memory task and recognition memory assessed by the RAVLT compared to healthy controls. Model-based analysis did not show significant differences between groups. On the other hand, model-free analysis identified components that fitted the task-model and were common to all the participants, as well as components that differed between PD and healthy controls. PD patients showed decreased task-related activations in areas involved in the recognition memory network and decreased task-related deactivations in the default mode network in comparison with controls. In conclusion, model-free fMRI analysis detected alterations in functional cerebral networks involved in a verbal memory task in PD patients without evident recognition memory deficit.

Assessing manual pursuit tracking in Parkinson's disease via linear dynamical systems

Quantitative assessment of motor performance is important for diseases of motor control, such as Parkinson's disease (PD). Manual tracking tasks are well suited for motor assessment, as they can be performed concomitantly with brain mapping techniques. Here we propose utilizing second-order linear dynamical systems to assess manual pursuit tracking performance. With the desired trajectory as the input, and the subject's actual motor response as the output, a linear model characterized by natural frequency and damping ratio is identified for each subject. We applied this method to 10 PD subjects (on and off L: -dopa medication) and 10 normal subjects performing a multi-frequency sinusoidal tracking task. Model parameters were more sensitive than overall tracking errors in determining significant differences between groups. The effect of L: -dopa medication was to reduce the damping ratio and make the range in natural frequency across individuals approach that of normal subjects. We interpret the changes in damping ratio and natural frequency as possibly related to suppression of compensatory cerebellar activity and/or improvement of motor program selection, and the changes in natural frequency as an implicit strategy to maintain settling time in the face of reduce damping ratio. Our results suggest that simple linear dynamical system models can be a powerful method to assess tracking performance in Parkinson's disease because of the additional insight they can provide into neurological processes.

Systematic review of levodopa dose equivalency reporting in Parkinson's disease

Interpretation of clinical trials comparing different drug regimens for Parkinson's disease (PD) is complicated by the different dose intensities used: higher doses of levodopa and, possibly, other drugs produce better symptomatic control but more late complications. To address this problem, conversion factors have been calculated for antiparkinsonian drugs that yield a total daily levodopa equivalent dose (LED). LED estimates vary, so we undertook a systematic review of studies reporting LEDs to provide standardized formulae. Electronic database and hand searching of references identified 56 primary reports of LED estimates. Data were extracted and the mean and modal LEDs calculated. This yielded a standardized LED for each drug, providing a useful tool to express dose intensity of different antiparkinsonian drug regimens on a single scale. Using these conversion formulae to report LEDs would improve the consistency of reporting and assist the interpretation of clinical trials comparing different PD medications.

Impulse control disorders following deep brain stimulation of the subthalamic nucleus in Parkinson's disease: clinical aspects

Parkinson's disease (PD) has been associated with the development of impulse control disorders (ICDs), possibly due to overstimulation of the mesolimbic system by dopaminergic medication. Preliminary reports have suggested that deep brain stimulation (DBS), a neurosurgical procedure offered to patients with treatment-resistant PD, affects ICD in a twofold way. Firstly, DBS allows a decrease in dopaminergic medication and hence causes an improvement in ICDs. Secondly, some studies have proposed that specific ICDs may develop after DBS. This paper addresses the effects of DBS on ICDs in patients with PD. A literature search identified four original studies examining a total of 182 patients for ICDs and nine case reports of 39 patients that underwent DBS and developed ICDs at some point. Data analysis from the original studies did not identify a significant difference in ICDs between patients receiving dopaminergic medication and patients on DBS, whilst the case reports showed that 56% of patients undergoing DBS had poor outcome with regards to ICDs. We discuss these ambivalent findings in the light of proposed pathogenetic mechanisms. Longitudinal, prospective studies with larger number of patients are required in order to fully understand the role of DBS on ICDs in patients with PD.

Intra- and inter-limb coherency during stance in non-dyskinetic and dyskinetic patients with Parkinson's disease

OBJECTIVE

Examine the level of intra- and inter-limb coherency in non-dyskinetic and dyskinetic patients with Parkinson's disease (PD).

PATIENTS & METHODS

Using a magnetic tracking system, whole-body 3D movements were assessed in 10 dyskinetic patients with clear monophasic peak-dose levodopa-induced dyskinesia (LID), in 10 non-dyskinetic patients and in 10 control subjects, standing with their arms out. Patients were tested during their best ON period. Coherency in the kinematics of pairs of body segments was assessed by spectral analysis. For each pair examined, we calculated the highest coherency between 0.5 and 3.0Hz and the frequency at which this maximum coherency occurred.

RESULTS

Analysis of variance showed that for 34 out of the 44 (77.3%) comparisons we studied, there were significant differences between the means of coherencies of the groups. Typically, the control group had the highest coherency and the patients with LID had the lowest. Patients with LID also tended to have their maximum coherency at higher frequencies than the control and non-dyskinetic patient groups (30 out of 44 comparisons were significant). These trends appeared in all types of inter-segment comparisons, including bilaterally symmetric segments, biomechanically linked segments (in which coherencies were higher overall in all groups, but still different between groups) and in other comparisons, but the trends were not so clear for comparisons involving the feet.

CONCLUSION

LID is indeed incoherent in the frequency domain, suggesting that body segments may be driven by different neural outputs. The challenges of dealing with these incoherent involuntary movements when planning and executing voluntary movements must certainly play a role in motor difficulties observed in patients with LID. The fact that both dyskinetic and non-dyskinetic patients showed less coherency than controls suggests that levodopa may alter postural control by decreasing stiffness and increasing limb independence.

Cerebrospinal tau, phospho-tau, and beta-amyloid and neuropsychological functions in Parkinson's disease

Alzheimer's disease (AD)-pathology may play a role in Parkinson's disease (PD)-related dementia (PDD). The aim of this study was to assess cerebrospinal fluid (CSF) levels of tau, phospho-tau, and beta-amyloid, proposed AD biomarkers, and their relationship with cognitive function in PD. Forty PD patients [20 nondemented (PDND); 20 PDD] and 30 controls underwent CSF tau, phospho-tau, and beta-amyloid analysis using specific ELISA techniques. All PD patients and 15 controls underwent neuropsychological testing of fronto-subcortical (attention, fluency) and neocortical (memory, naming, visuoperceptive) functions. CSF markers levels were compared between groups, and compared and correlated with neuropsychological measures in PDND and PDD separately and as a continuum (PD). CSF tau and phospho-tau were higher in PDD than in PDND and controls (P < 0.05). CSF beta-amyloid ranged from high (controls) to intermediate (PDND) and low (PDD) levels (P < 0.001). In all PD and PDD patients, high CSF tau and phospho-tau were associated with impaired memory and naming. In PDND, CSF beta-amyloid was related with phonetic fluency. These findings suggest underlying AD-pathology in PDD in association with cortical cognitive dysfunction, and that low CSF beta-amyloid in PDND patients with impaired phonetic fluency can constitute an early marker of cognitive dysfunction.

Cerebrospinal hypocretin, daytime sleepiness and sleep architecture in Parkinson's disease dementia

Excessive daytime sleepiness is common in Parkinson's disease and has been associated with Parkinson's disease-related dementia. Narcoleptic features have been observed in Parkinson's disease patients with excessive daytime sleepiness and hypocretin cell loss has been found in the hypothalamus of Parkinson's disease patients, in association with advanced disease. However, studies on cerebrospinal fluid levels of hypocretin-1 (orexin A) in Parkinson's disease have been inconclusive. Reports of sleep studies in Parkinson's disease patients with and without excessive daytime sleepiness have also been disparate, pointing towards a variety of causes underlying excessive daytime sleepiness. In this study, we aimed to measure cerebrospinal fluid hypocretin-1 levels in Parkinson's disease patients with and without dementia and to study their relationship to dementia and clinical excessive daytime sleepiness, as well as to describe potentially related sleep architecture changes. Twenty-one Parkinson's disease patients without dementia and 20 Parkinson's disease patients with dementia, along with 22 control subjects without sleep complaints, were included. Both Epworth sleepiness scale, obtained with the help of the caregivers, and mini-mental state examination were recorded. Lumbar cerebrospinal fluid hypocretin-1 levels were measured in all individuals using a radio-immunoassay technique. Additionally, eight Parkinson's disease patients without dementia and seven Parkinson's disease patients with dementia underwent video-polysomnogram and multiple sleep latencies test. Epworth sleepiness scale scores were higher in Parkinson's disease patients without dementia and Parkinson's disease patients with dementia than controls (P < 0.01) and scores >10 were more frequent in Parkinson's disease patients with dementia than in Parkinson's disease patients without dementia (P = 0.04). Cerebrospinal fluid hypocretin-1 levels were similar among groups (controls = 321.15 +/- 47.15 pg/ml; without dementia = 300.99 +/- 58.68 pg/ml; with dementia = 309.94 +/- 65.95 pg/ml; P = 0.67), and unrelated to either epworth sleepiness scale or mini-mental state examination. Dominant occipital frequency awake was slower in Parkinson's disease patients with dementia than Parkinson's disease patients without dementia (P = 0.05). Presence of slow dominant occipital frequency and/or loss of normal non-rapid eye movement sleep architecture was more frequent among Parkinson's disease patients with dementia (P = 0.029). Thus, excessive daytime sleepiness is more frequent in Parkinson's disease patients with dementia than Parkinson's disease patients without dementia, but lumbar cerebrospinal fluid hypocretin-1 levels are normal and unrelated to severity of sleepiness or the cognitive status. Lumbar cerebrospinal fluid does not accurately reflect the hypocretin cell loss known to occur in the hypothalamus of advanced Parkinson's disease. Alternatively, mechanisms other than hypocretin cells dysfunction may be responsible for excessive daytime sleepiness and the sleep architecture alterations seen in these patients.

Coordination of grasping and walking in Parkinson's disease

Studies on grasp control underlying manual dexterity in people with Parkinson disease (PD) suggest that anticipatory grasp control is mainly unaffected during discrete tasks using simple two-digit grasp. Nevertheless, impaired hand function during daily activities is one of the most disabling symptoms of PD. As many daily grasping activities occur during functional movements involving the whole body, impairments in anticipatory grasp control might emerge during a continuous dynamic task such as object transport during walking. In this case, grasp control must be coordinated along with multiple body segments. The present study investigated the effect of PD on anticipatory grasp control and intersegmental coordination during walking with a hand-held object. Nine individuals with idiopathic PD (tested OFF and ON medication) and nine healthy age-matched controls carried a grip instrument between their right thumb and index finger during self-paced and fast walking. Although the amplitude of grip forces was higher in standing and walking for subjects with PD, both subjects with PD and control subjects coupled grip and inertial force changes in an anticipatory fashion while walking. However, gait-induced motions of the object relative to that of the trunk (i.e., dampening) was reduced in subjects with PD. Medication increased the dampening in all subjects with PD. We suggest that these differences are associated with impairments in intersegmental coordination.

L-dopa induces under-damped visually guided motor responses in Parkinson's disease

Parkinson's disease preferentially affects internally generated movements, e.g., movements recalled from memory, while externally cued movements are relatively preserved. However, L-dopa may have effects on visually guided movements as well as error-related processing. Fourteen Parkinson's disease (PD) subjects (on and off L-dopa medication) as well as ten normal controls performed a tracking task using a joystick. During discrete 30 s blocks, the visual feedback of the actual tracking errors were attenuated, amplified or unaltered. Second order dynamical system models, with the desired trajectory as the input and the actual motor performance as the output, were used to characterize the motor performance by the each subject under each condition. Although the overall root-mean-square tracking error did not significantly differ between groups, the nature of the motor performance differed significantly across groups. A clear dissociation was made between manipulations of error feedback--which altered the natural frequency of the models--and the effects of L-dopa, which affected damping. Compared to normal controls, PD subjects were significantly overdamped before medication and underdamped after medication. We interpret our results as being suggestive of L: -dopa normalization of compensatory overactive cerebellar activity in PD.