Magnetic Resonance-Guided Focused Ultrasound (MRgFUS)-Thalamotomy for Essential Tremor: Lesion Location and Clinical Outcomes.

BACKGROUND: Factors predicting clinical outcomes after MR-guided focused ultrasound (MRgFUS)-thalamotomy in patients with essential tremor (ET) are not well known. OBJECTIVE: To examine the clinical outcomes and their relationship with patients' baseline demographic and clinical features and lesion characteristics at 6-month follow-up in ET patients. METHODS: A total of 127 patients were prospectively evaluated at 1 (n = 122), 3 (n = 102), and 6 months (n = 78) after MRgFUS-thalamotomy. Magnetic resonance imaging (MRI) was obtained at 6 months (n = 60). Primary outcomes included: (1) change in the Clinical Rating Scale of Tremor (CRST)-A+B score in the treated hand and (2) frequency and severity of adverse events (AEs) at 6 months. Secondary outcomes included changes in all subitems of the CRST scale in the treated hand, CRST-C, axial tremor (face, head, voice, tongue), AEs, and correlation of primary outcomes at 6 months with lesion characteristics. Statistical analysis included linear mixed, standard, and logistic regression models. RESULTS: Scores for CRST-A+B, CRST-A, CRST-B in the treated hand, CRST-C, and axial tremor were improved at each evaluation (P < 0.001). Five patients had severe AEs at 1 month that became mild throughout the follow-up. Mild AEs occurred in 71%, 45%, and 34% of patients at 1, 3, and 6 months, respectively. Lesion volume was associated with the reduction in the CRST-A (P = 0.003) and its overlapping with the ventralis intermedius nucleus (Vim) nucleus with the reduction in CRST-A+B (P = 0.02) and CRST-B (P = 0.008) at 6 months. CONCLUSIONS: MRgFUS-thalamotomy improves hand and axial tremor in ET patients. Transient and mild AEs are frequent. Lesion volume and location are associated with tremor reduction. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Management of Impulse Control and Related Disorders in Parkinson's Disease: An Expert Consensus.

BACKGROUND: Impulse-control and related behavioral disorders (ICBDs) significantly impact the lives of Parkinson's disease (PD) patients and caregivers, with lasting consequences if undiagnosed and untreated. While ICBD pathophysiology and risk factors are well-studied, a standardized severity definition and treatment evidence remain elusive. OBJECTIVE: This work aimed to establish international expert consensus on ICBD treatment strategies. To comprehensively address diverse treatment availabilities, experts from various continents were included. METHODS: From 2021 to 2023, global movement disorders specialists engaged in a Delphi process. A core expert group initiated surveys, involving a larger panel in three iterations, leading to refined severity definitions and treatment pathways. RESULTS: Experts achieved consensus on defining ICBD severity, emphasizing regular PD patient screenings for early detection. General treatment recommendations focused on continuous monitoring, collaboration with significant others, and seeking specialist advice for legal or financial challenges. For mild to severe ICBDs, gradual reduction in dopamine agonists was endorsed, followed by reductions in other PD medications. Second-line treatment strategies included diverse approaches like reversing the last medication change, cognitive behavior therapy, subthalamic nucleus deep brain stimulation, and specific medications like quetiapine, clozapine, and antidepressants. The panel reached consensus on distinct treatment pathways for punding and dopamine dysregulation syndrome, formulating therapy recommendations. Comprehensive discussions addressed management strategies for the exacerbation of either motor or non-motor symptoms following the proposed treatments. CONCLUSION: The consensus offers in-depth insights into ICBD management, presenting clear severity criteria and expert consensus treatment recommendations. The study highlights the critical need for further research to enhance ICBD management. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Cerebral metabolic pattern associated with progressive parkinsonism in non-human primates reveals early cortical hypometabolism.

Dopaminergic denervation in patients with Parkinson's disease is associated with changes in brain metabolism. Cerebral in-vivo mapping of glucose metabolism has been studied in severe stable parkinsonian monkeys, but data on brain metabolic changes in early stages of dopaminergic depletion of this model is lacking. Here, we report cerebral metabolic changes associated with progressive nigrostriatal lesion in the pre-symptomatic and symptomatic stages of the progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) monkey model of Parkinson's Disease. Monkeys (Macaca fascicularis) received MPTP injections biweekly to induce progressive grades of dopamine depletion. Monkeys were sorted according to motor scale assessments in control, asymptomatic, recovered, mild, and severe parkinsonian groups. Dopaminergic depletion in the striatum and cerebral metabolic patterns across groups were studied in vivo by positron emission tomography (PET) using monoaminergic ([11C]-dihydrotetrabenazine; 11C-DTBZ) and metabolic (2-[18F]-fluoro-2-deoxy-d-glucose; 18F-FDG) radiotracers. 11C-DTBZ-PET analysis showed progressive decrease of binding potential values in the striatum of monkeys throughout MPTP administration and the development of parkinsonian signs. 18F-FDG analysis in asymptomatic and recovered animals showed significant hypometabolism in temporal and parietal areas of the cerebral cortex in association with moderate dopaminergic nigrostriatal depletion. Cortical hypometabolism extended to involve a larger area in mild parkinsonian monkeys, which also exhibited hypermetabolism in the globus pallidum pars interna and cerebellum. In severe parkinsonian monkeys, cortical hypometabolism extended further to lateral-frontal cortices and hypermetabolism also ensued in the thalamus and cerebellum. Unbiased histological quantification of neurons in Brodmann's area 7 in the parietal cortex did not reveal neuron loss in parkinsonian monkeys versus controls. Early dopaminergic nigrostriatal depletion is associated with cortical, mainly temporo-parietal hypometabolism unrelated to neuron loss. These findings, together with recent evidence from Parkinson's Disease patients, suggest that early cortical hypometabolism may be associated and driven by subcortical changes that need to be evaluated appropriately. Altogether, these findings could be relevant when potential disease modifying therapies become available.

Abnormal pattern of brain glucose metabolism in Parkinson's disease: replication in three European cohorts.

RATIONALE: In Parkinson's disease (PD), spatial covariance analysis of 18F-FDG PET data has consistently revealed a characteristic PD-related brain pattern (PDRP). By quantifying PDRP expression on a scan-by-scan basis, this technique allows objective assessment of disease activity in individual subjects. We provide a further validation of the PDRP by applying spatial covariance analysis to PD cohorts from the Netherlands (NL), Italy (IT), and Spain (SP). METHODS: The PDRPNL was previously identified (17 controls, 19 PD) and its expression was determined in 19 healthy controls and 20 PD patients from the Netherlands. The PDRPIT was identified in 20 controls and 20 "de-novo" PD patients from an Italian cohort. A further 24 controls and 18 "de-novo" Italian patients were used for validation. The PDRPSP was identified in 19 controls and 19 PD patients from a Spanish cohort with late-stage PD. Thirty Spanish PD patients were used for validation. Patterns of the three centers were visually compared and then cross-validated. Furthermore, PDRP expression was determined in 8 patients with multiple system atrophy. RESULTS: A PDRP could be identified in each cohort. Each PDRP was characterized by relative hypermetabolism in the thalamus, putamen/pallidum, pons, cerebellum, and motor cortex. These changes co-varied with variable degrees of hypometabolism in posterior parietal, occipital, and frontal cortices. Frontal hypometabolism was less pronounced in "de-novo" PD subjects (Italian cohort). Occipital hypometabolism was more pronounced in late-stage PD subjects (Spanish cohort). PDRPIT, PDRPNL, and PDRPSP were significantly expressed in PD patients compared with controls in validation cohorts from the same center (P < 0.0001), and maintained significance on cross-validation (P < 0.005). PDRP expression was absent in MSA. CONCLUSION: The PDRP is a reproducible disease characteristic across PD populations and scanning platforms globally. Further study is needed to identify the topography of specific PD subtypes, and to identify and correct for center-specific effects.

Functional inhibitory control dynamics in impulse control disorders in Parkinson's disease.

BACKGROUND: Impulse control disorders related to alterations in the mesocorticolimbic dopamine network occur in Parkinson's disease (PD). Our objective was to investigate the functional neural substrates of reward processing and inhibitory control in these patients. METHODS: Eighteen PD patients with impulse control disorders, 17 without this complication, and 18 healthy controls performed a version of the Iowa Gambling Task during functional magnetic resonance scanning under 3 conditions: positive, negative, and mixed feedback. Whole-brain contrasts, regions of interest, time courses, functional connectivity analyses, and brain-behavior associations were examined. RESULTS: PD patients with impulse control disorders exhibited hyperactivation in subcortical and cortical regions typically associated with reward processing and inhibitory control compared with their PD and healthy control counterparts. Time-course analyses revealed that only PD patients with impulse control disorders exhibited stronger signal intensity during the initial versus final periods of the negative-feedback condition in bilateral insula, and right ventral striatum. Interestingly, hyperactivation of all the examined right-lateralized frontostriatal areas during negative feedback was positively associated with impulse control disorder severity. Importantly, positive associations between impulse control disorder severity and regional activations in the right insula and right inferior frontal gyrus, but not the right subthalamic nucleus, were mediated by functional connectivity with the right ventral striatum. CONCLUSIONS: During a reward-based task, PD patients with impulse control disorders showed hyperactivation in a right-lateralized network of regions including the subthalamic nucleus that was strongly associated with impulse control disorder severity. In these patients, the right ventral striatum in particular played a critical role in modulating the functional dynamics of right-lateralized inhibitory-control frontal regions when facing penalties. © 2019 International Parkinson and Movement Disorder Society.

Nigrostriatal dopamine transporter availability, and its metabolic and clinical correlates in Parkinson's disease patients with impulse control disorders.

PURPOSE: Previous studies in patients with Parkinson's disease (PD) and impulse control disorders (ICDs) have produced heterogeneous results regarding striatal dopamine transporter (DaT) binding and activity in the mesocorticolimbic network. Our aim here was to study the relationship between striatal DaT availability and cortical metabolism, as well as motor, behavioural and cognitive features of PD patients with ICD. METHODS: In a group of PD patients with ICD (PD-ICD, n = 16) and 16 matched PD patients without ICD (PD-noICD, n = 16), DaT single-photon emission computed tomography (SPECT) imaging (DaTSCAN) was used to study DaT availability in predefined striatal volumes of interest (VOIs): putamen, caudate nucleus and ventral striatum (VS). In addition, the specific association of striatal DaT binding with cortical limbic and associative metabolic activity was evaluated by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in PD-ICD patients and investigated using statistical parametric mapping (SPM8). Finally, associations between DaT availability and motor, behavioural and cognitive features were assessed. RESULTS: PD-ICD patients had a significantly lower DaT density in the VS than PD-noICD patients, which was inversely associated with ICD severity. Lower DaT availability in the VS was associated with lower FDG uptake in several cortical areas belonging to the limbic and associative circuits, and in other regions involved in reward and inhibition processes (p < 0.0001 uncorrected; k > 50 voxels). No significant results were observed using a higher conservative threshold (p < 0.05; FDR corrected). PD-ICD patients also displayed impairment in interference and attentional Stroop Task execution, and more anxiety, all associated with reduced DaT availability in the VS and caudate nucleus. CONCLUSIONS: ICDs in PD patients are related to reduced DaT binding in the VS, which accounts for dysfunction in a complex cortico-subcortical network that involves areas of the mesolimbic and mesocortical systems, being associated with reward evaluation, salience attribution and inhibitory control processes.

Subthalamotomy for Parkinson's disease: clinical outcome and topography of lesions.

OBJECTIVE: Subthalamotomy is an effective alternative for the treatment of Parkinson's disease (PD). However, uncertainty about the optimal target location and the possibility of inducing haemichorea-ballism have limited its application. We assessed the correlation between the topography of radiofrequency-based lesions of the subthalamic nucleus (STN) with motor improvement and the emergence of haemichorea-ballism. METHODS: Sixty-four patients with PD treated with subthalamotomy were evaluated preoperatively and postoperatively using the Unified Parkinson's Disease Rating Scale motor score (UPDRSm), MRI and tractography. Patients were classified according to the degree of clinical motor improvement and dyskinesia scale. Lesions were segmented on MRI and averaged in a standard space. We examined the relationship between the extent of lesion-induced disruption of fibres surrounding the STN and the development of haemichorea-ballism. RESULTS: Maximum antiparkinsonian effect was obtained with lesions located within the dorsolateral motor region of the STN as compared with those centre-placed in the dorsal border of the STN and the zona incerta (71.3%, 53.5% and 20.8% UPDRSm reduction, respectively). However, lesions that extended dorsally beyond the STN showed lower probability of causing haemichorea-ballism than those placed entirely within the nucleus. Tractography findings indicate that interruption of pallidothalamic fibres probably determines a low probability of haemichorea-ballism postoperatively. CONCLUSIONS: The topography of the lesion is a major factor in the antiparkinsonian effect of subthalamotomy in patients with PD. Lesions involving the motor STN and pallidothalamic fibres induced significant motor improvement and were associated with a low incidence of haemichorea-ballism.

Ratios of proteins in cerebrospinal fluid in Parkinson's disease cognitive decline: prospective study.

BACKGROUND: There is a need for biomarkers of dementia in PD. OBJECTIVES: To determine if the levels of the main CSF proteins and their ratios are associated with deterioration in cognition and progression to dementia in the short to mid term. METHODS: The Parkinson's Progression Markers Initiative database was used as an exploratory cohort, and a center-based cohort was used as a replication cohort. Amyloid ß1-42, total tau, threonine-181 phosphorylated tau, and α-synuclein in the CSF and the ratios of these proteins were assessed. RESULTS: In the Parkinson's Progression Markers Initiative cohort (n = 281), the total tau/amyloid ß1-42, total tau/α-synuclein, total tau/amyloid ß1-42+α-synuclein, and amyloid ß1-42/total tau ratios were associated with a risk of progression to dementia over a 3-year follow-up. In the replication cohort (n = 40), the total tau/α-synuclein and total tau/amyloid ß1-42+α-synuclein ratios were associated with progression to dementia over a 41-month follow-up. CONCLUSION: Ratios of the main proteins found in PD patient brain inclusions that can be measured in the CSF appear to have value as short- to mid-term predictors of dementia. © 2018 International Parkinson and Movement Disorder Society.

Detecting Mild Cognitive Deficits in Parkinson's Disease: Comparison of Neuropsychological Tests.

BACKGROUND: Numerous neuropsychological tests and test versions are used in Parkinson's disease research, but their relative capacity to detect mild cognitive deficits and their comparability across studies are unknown. The objective of this study was to identify neuropsychological tests that consistently detect cognitive decline in PD across studies. METHODS: Data from 30 normed neuropsychological tests across 20 international studies in up to 2908 nondemented PD patients were analyzed. A subset of 17 tests was administered to up to 1247 healthy controls. A 2-step meta-analytic approach using standardized scores compared performance in PD with normative data. RESULTS: Pooled estimates of the differences between PD and site-specific healthy controls identified significant cognitive deficits in PD patients on 14 test scores across 5 commonly assessed cognitive domains (attention or working memory, executive, language, memory, and visuospatial abilities), but healthy control performance was statistically above average on 7 of these tests. Analyses based on published norms only, as opposed to direct assessment of healthy controls, showed high between-study variability that could not be accounted for and led to inconclusive results. CONCLUSIONS: Normed neuropsychological tests across multiple cognitive domains consistently detect cognitive deficits in PD when compared with site-specific healthy control performance, but relative PD performance was significantly affected by the inclusion and type of healthy controls versus the use of published norms only. Additional research is needed to identify a cognitive battery that can be administered in multisite international studies and that is sensitive to cognitive decline, responsive to therapeutic interventions, and superior to individual cognitive tests. © 2018 International Parkinson and Movement Disorder Society.

Treatable inherited rare movement disorders.

There are many rare movement disorders, and new ones are described every year. Because they are not well recognized, they often go undiagnosed for long periods of time. However, early diagnosis is becoming increasingly important. Rapid advances in our understanding of the biological mechanisms responsible for many rare disorders have enabled the development of specific treatments for some of them. Well-known historical examples include Wilson disease and dopa-responsive dystonia, for which specific and highly effective treatments have life-altering effects. In recent years, similarly specific and effective treatments have been developed for more than 30 rare inherited movement disorders. These treatments include specific medications, dietary changes, avoidance or management of certain triggers, enzyme replacement therapy, and others. This list of treatable rare movement disorders is likely to grow during the next few years because a number of additional promising treatments are actively being developed or evaluated in clinical trials. © 2017 International Parkinson and Movement Disorder Society.

Tau/α-synuclein ratio and inflammatory proteins in Parkinson's disease: An exploratory study.

BACKGROUND: No CSF or plasma biomarker has been validated for diagnosis or progression of PD. OBJECTIVES: To assess whether the CSF and plasma levels of proteins associated with PD neuropathological inclusions and with neuroinflammation might have value in the diagnosis of PD or in relation to disease severity. METHODS: CSF levels of α-synuclein, amyloid-ß1-42, total tau, and threonine-181 phosphorylated tau, as well as CSF and plasma levels of cytokines (interleukin-1ß, interleukin-2, interleukin, interferon-γ, and tumor necrosis factor α) were studied in 40 PD patients and 40 healthy controls. Plasma levels of cytokines were measured in 51 patients and 26 aditional controls. We also explored the Parkinson's Progression Markers Initiative data set as a replication cohort. RESULTS: CSF levels of α-synuclein, amyloid-ß1-42, and tumor necrosis factor α were lower in patients than in controls, and the total tau/α-synuclein, phosphorylated tau/α-synuclein, total tau/amyloid-ß1-42+α-synuclein, and phosphorylated tau/amyloid-ß1-42+α-synuclein ratios were higher in patients. The best area under the curve value was obtained for the phosphorylated tau/α-synuclein ratio alone (0.86) and also when this was combined with tumor necrosis factor α in CSF (0.91; sensitivity 92.9%, specificity 75% for a cut-off value of ≤ 0.71). Phosphorylated tau/α-synuclein and phosphorylated tau/amyloid-ß1-42+α-synuclein were higher in patients than in controls of the Parkinson's Progression Markers Initiative database. Plasma cytokines did not differ between groups, although interleukin-6 levels were positively correlated with UPDRS-I, -II, and -III scores. CONCLUSIONS: The CSF phosphorylated tau/α-synuclein ratio alone, and in combination with tumor necrosis factor α and plasma interleukin-6 levels, might serve as biomarkers to diagnose PD and monitor its severity. © 2017 International Parkinson and Movement Disorder Society.

Significance of visual hallucinations and cerebral hypometabolism in the risk of dementia in Parkinson's disease patients with mild cognitive impairment.

INTRODUCTION: Mild cognitive impairment (MCI) and visual hallucinations (VH) are common co-morbidities and risk factors for dementia in Parkinson's disease (PD). The relative value of each of them in the progression to dementia is unknown. We investigated cognitive impairment and cerebral hypometabolism in PD-MCI patients with VH (VH-positive) and without (VH-negative). METHODS: Twenty-one PD-MCI patients (12 VH-negative, nine VH-positive) and 19 controls were studied using a comprehensive neuropsychological battery and [18F]-Fluorodeoxyglucose positron emission tomography (FDG-PET). The neuropsychological assessment was repeated after 30 months. Regional FDG uptake was analyzed using statistical parametric mapping. RESULTS: VH-positive patients had lower FDG uptake bilaterally in the occipital, and parietal cortex, right temporal lobe and in the left cingulum compared with VH-negative patients. The two groups showed no significant differences in clinical characteristics and cognitive status at baseline. After 30 months of follow-up, three (25%) and four (50%) of the VH-negative and VH-positive patients, respectively, had progressed to dementia. CONCLUSION: Even in the absence of significant cognitive differences, PD-MCI patients with VH exhibit more severe cerebral hypometabolism and had a higher rate of progression to dementia than VH-negative patients, supporting the importance of VH and cerebral hypometabolism in establishing the risk of dementia in PD-MCI.

Biomarkers for dementia and mild cognitive impairment in Parkinson's disease.

Cognitive decline is one of the most frequent and disabling nonmotor features of Parkinson's disease. Around 30% of patients with Parkinson's disease experience mild cognitive impairment, a well-established risk factor for the development of dementia. However, mild cognitive impairment in patients with Parkinson's disease is a heterogeneous entity that involves different types and extents of cognitive deficits. Because it is not currently known which type of mild cognitive impairment confers a higher risk of progression to dementia, it would be useful to define biomarkers that could identify these patients to better study disease progression and possible interventions. In this sense, the identification among patients with Parkinson's disease and mild cognitive impairment of biomarkers associated with dementia would allow the early detection of this process. This review summarizes studies from the past 25 years that have assessed the potential biomarkers of dementia and mild cognitive impairment in Parkinson's disease patients. Despite the potential importance, no biomarker has as yet been validated. However, features such as low levels of epidermal and insulin-like growth factors or uric acid in plasma/serum and of Aß in CSF, reduction of cerebral cholinergic innervation and metabolism measured by PET mainly in posterior areas, and hippocampal atrophy in MRI might be indicative of distinct deficits with a distinct risk of dementia in subgroups of patients. Longitudinal studies combining the existing techniques and new approaches are needed to identify patients at higher risk of dementia. © 2016 International Parkinson and Movement Disorder Society.

The expanding universe of disorders of the basal ganglia.

The basal ganglia were originally thought to be associated purely with motor control. However, dysfunction and pathology of different regions and circuits are now known to give rise to many clinical manifestations beyond the association of basal ganglia dysfunction with movement disorders. Moreover, disorders that were thought to be caused by dysfunction of the basal ganglia only, such as Parkinson's disease and Huntington's disease, have diverse abnormalities distributed not only in the brain but also in the peripheral and autonomic nervous systems; this knowledge poses new questions and challenges. We discuss advances and the unanswered questions, and ways in which progress might be made.

Goal-directed and habitual control in the basal ganglia: implications for Parkinson's disease.

Progressive loss of the ascending dopaminergic projection in the basal ganglia is a fundamental pathological feature of Parkinson's disease. Studies in animals and humans have identified spatially segregated functional territories in the basal ganglia for the control of goal-directed and habitual actions. In patients with Parkinson's disease the loss of dopamine is predominantly in the posterior putamen, a region of the basal ganglia associated with the control of habitual behaviour. These patients may therefore be forced into a progressive reliance on the goal-directed mode of action control that is mediated by comparatively preserved processing in the rostromedial striatum. Thus, many of their behavioural difficulties may reflect a loss of normal automatic control owing to distorting output signals from habitual control circuits, which impede the expression of goal-directed action.

The relationship between atrophy and hypometabolism: is it regionally dependent in dementias?

Neuronal failure leading to dementia in neurodegenerative diseases is evidenced in vivo by functional and structural changes in the brain such as reductions of glucose consumption and volume of grey matter. The earliest phase of cognitive decline and presymptomatic stages of these diseases are heralded by specific patterns of hypometabolism, even in the absence of atrophy, which are currently considered as diagnostic biomarkers. Atrophy is less consistently found as an initial marker of these diseases and is invariably present in moderate to severe stages with a disease-related topography. The relationship between these two markers is not uniform, but in the two diseases in which they have been directly compared, Alzheimer's and Parkinson's disease, altered hypometabolism precedes and exceeds atrophy in most regions. This suggests a two-step degenerative process. In contrast to these findings, the hippocampus skips this pattern and is more structurally than functionally affected, thereby suggesting a different pathological mechanism in this particular area. More studies are needed to disentangle the mechanisms underlying both markers and their relationship in neurodegenerative diseases.

Grey matter hypometabolism and atrophy in Parkinson's disease with cognitive impairment: a two-step process.

The pathophysiological process underlying cognitive decline in Parkinson's disease is not well understood. Cerebral atrophy and hypometabolism have been described in patients with Parkinson's disease and dementia or mild cognitive impairment with respect to control subjects. However, the exact relationships between atrophy and hypometabolism are still unclear. To determine the extension and topographical distribution of hypometabolism and atrophy in the different cognitive states of Parkinson's disease, we examined 46 patients with Parkinson's disease (19 female, 27 male; 71.7 ± 5.9 years old; 14.6 ± 4.2 years of disease evolution; modified Hoehn and Yahr mean stage 3.1 ± 0.7). Cognitive status was diagnosed as normal in 14 patients, as mild cognitive impairment in 17 and as dementia in 15 patients. Nineteen normal subjects (eight female, 11 male; 68.1 ± 3.2 years old) were included as controls. (18)F-fluorodeoxyglucose positron emission tomography and magnetic resonance imaging scans were obtained, co-registered, corrected for partial volume effect and spatially normalized to the Montreal Neurological Institute space in each subject. Smoothing was applied to the positron emission tomography and magnetic resonance imaging scans to equalize their effective smoothness and resolution (10 mm and 12 mm full-width at half-maximum and Gaussian kernel, respectively). Z-score maps for atrophy and for hypometabolism were obtained by comparing individual images to the data set of control subjects. For each group of patients, a paired Student's t-test was performed to statistically compare the two Z-map modalities (P < 0.05 false discovery rate corrected) using the direct voxel-based comparison technique. In patients with mild cognitive impairment, hypometabolism exceeded atrophy in the angular gyrus, occipital, orbital and anterior frontal lobes. In patients with dementia, the hypometabolic areas observed in the group with mild cognitive impairment were replaced by areas of atrophy, which were surrounded by extensive zones of hypometabolism. Areas where atrophy was more extended than hypometabolism were found in the precentral and supplementary motor areas in both patients with mild cognitive impairment and with dementia, and in the hippocampus and temporal lobe in patients with dementia. These findings suggest that there is a gradient of severity in cortical changes associated with the development of cognitive impairment in Parkinson's disease in which hypometabolism and atrophy represent consecutive stages of the same process in most of the cortical regions affected.

The subthalamic nucleus and inhibitory control: impact of subthalamotomy in Parkinson's disease.

The aim of our study was to investigate two inter-related hypotheses about the role of the subthalamic nucleus. First that the subthalamic nucleus plays a role in adjusting response thresholds and speed-accuracy trade-offs and second that it is involved in reactive and proactive inhibition and conflict resolution. These were addressed by comparing the performance of 10 patients with Parkinson's disease treated with right subthalamotomy and 12 patients with left subthalamotomy, to 14 unoperated patients with Parkinson's disease and 23 age-matched healthy control participants on a conditional stop signal task and applying the drift diffusion model. Unilateral subthalamotomy significantly improved Parkinson's disease motor signs. Patients with right subthalamotomy had significantly faster Go reaction times with their contra-lesional hand than the unoperated patients and did not differ from the control participants, indicating their speed of response initiation was 'normalized'. However, operated patients made significantly more discrimination errors than unoperated patients and controls, suggesting that subthalamotomy influenced speed-accuracy trade-offs. This was confirmed by the drift diffusion model, revealing that while the unoperated patients had significantly lower drift rate and higher response thresholds than the control participants, the response thresholds for the operated groups did not differ from the controls and the patients with right subthalamotomy had a significantly higher drift rate than unoperated patients and similar to that of controls. The drift diffusion model further established that unlike the control participants, operated patients failed to show context-dependent strategic modulation of response thresholds. The patients with right subthalamotomy could not engage in late phase, fast inhibition of the response and showed minimal proactive inhibition when tested with the contra-lesional hand. These results provide strong evidence that the subthalamic nucleus is involved in response inhibition, in modulating the rate of information accumulation and the response threshold and influencing the balance between speed and accuracy of performance. Accordingly, the subthalamic nucleus can be considered a key component of the cerebral inhibitory network.

Prevalence of cancer in Parkinson's disease related to R1441G and G2019S mutations in LRRK2.

An inverse relationship between Parkinson's disease (PD) and cancer has been described. However, the association between cancers and genetic forms of PD, in particular the R1441G mutation in the LRRK2 gene, is not well known. The objective of this work was to analyze cancer prevalence in PD patients with R1441G or G2019S mutations in LRRK2, and in idiopathic PD (iPD). A total of 732 patients with PD (70 and 25 carriers of R1441G or G2019S mutations, respectively), and 177 controls, were linked using a population-based cancer registry of the Spanish province of Gipuzkoa. Cancer prevalence was not significantly higher in PD-G2019S carriers (20%) than in PD-R1441G carriers (14.3%), iPD (13.8%), or controls (12.5%). With the exception of a high prevalence of hematological cancers (crude odds ratio of 7.1) in the R1441G group, specific cancer types were not increased in PD mutation carriers. In both the carrier and iPD groups, cancers were diagnosed after the onset of PD. PD patients had a similar prevalence of cancer to control subjects. There was no increased association between G2019S or R1441G mutations and any type of cancer. Although there was a higher prevalence of hematological cancers in the R1441G group, the low number of such cancers overall makes this finding of uncertain significance. There was a slightly higher but not statistically significant prevalence of non-skin cancers in the G2019S group, suggesting that further study to evaluate the association should be undertaken prior to ascribing an increased cancer risk to this population.