Body side and predominant motor features at the onset of Parkinson's disease are linked to motor and nonmotor progression

Huntington Disease: Linking Pathogenesis to the Development of Experimental Therapeutics

Huntington disease (HD) is an autosomal dominant neurodegenerative condition caused by a CAG trinucleotide expansion in the huntingtin gene. At present, the HD field is experiencing exciting times with the assessment for the first time in human subjects of interventions aimed at core disease mechanisms. Out of a portfolio of interventions that claim a potential disease-modifying effect in HD, the target huntingtin has more robust validation. In this review, we discuss the spectrum of huntingtin-lowering therapies that are currently being considered. We provide a critical appraisal of the validation of huntingtin as a drug target, describing the advantages, challenges, and limitations of the proposed therapeutic interventions. The development of these new therapies relies strongly on the knowledge of HD pathogenesis and the ability to translate this knowledge into validated pharmacodynamic biomarkers. Altogether, the goal is to support a rational drug development that is ethical and cost-effective. Among the pharmacodynamic biomarkers under development, the quantification of mutant huntingtin in the cerebral spinal fluid and PET imaging targeting huntingtin or phosphodiesterase 10A deserve special attention. Huntingtin-lowering therapeutics are eagerly awaited as the first interventions that may be able to change the course of HD in a meaningful way.

Advances in the Clinical Differential Diagnosis of Parkinson's Disease

The differential diagnosis of Parkinson's disease has widened considerably in recent years. This chapter aims to summarize the current knowledge on the clinical differential diagnoses of sporadic Parkinson's disease. As the number of monogenic familial Parkinson's disease variants and risk factors is growing, so is the number of appreciated etiologies of atypical parkinsonian and other pallidopyramidal syndromes. This work aims at summarizing the current knowledge on both motor and nonmotor neurological signs and symptoms that aid the clinical diagnosis of Parkinson's disease and its differential diagnoses.

Psychosis in Parkinson's Disease: Epidemiology, Pathophysiology, and Management

Psychotic symptoms are common in Parkinson's disease (PD) and are associated with poorer quality of life and increased caregiver burden. PD psychosis is correlated with several factors, such as more advanced disease, cognitive impairment, depression, and sleep disorders. The underlying causes of psychosis in PD thus involve a complex interplay between exogenous (e.g., drugs, intercurrent illnesses) and endogenous (e.g., PD disease pathology) factors. Current theories of the pathophysiology of PD psychosis have come from several neuropathological and neuroimaging studies that implicate pathways involving visual processing and executive function, including temporo-limbic structures and neocortical gray matter with altered neurotransmitter functioning (e.g., dopamine, serotonin, and acetylcholine). Treatment of PD psychosis requires a step-wise process, including initial careful investigation of treatable triggering conditions and a comprehensive evaluation with adjustment of PD medications and/or initiation of specific antipsychotic therapies. Clozapine remains the only recommended drug for the treatment of PD psychosis; however, because of regular blood monitoring, quetiapine is usually first-line therapy, although less efficacious. Emerging studies have focused on agents involving other neurotransmitters, including the serotonin 5-HT2A receptor inverse agonist pimavanserin, cholinesterase inhibitors, and antidepressants and anxiolytics.

Marked brain asymmetry with intact cognitive functioning in idiopathic Parkinson's disease: a longitudinal analysis

OBJECTIVE

A 71-year-old (MN) with an 11-year history of left onset tremor diagnosed as Parkinson's disease (PD) completed longitudinal brain magnetic resonance imaging (MRI) and neuropsychological testing. MRI scans showed an asymmetric caudate nucleus (right < left volume). We describe this asymmetry at baseline and the progression over time relative to other subcortical gray, frontal white matter, and cortical gray matter regions of interest. Isolated structural changes are compared to MN's cognitive profiles.

METHOD

MN completed yearly MRIs and neuropsychological assessments. For comparison, left onset PD (n = 15) and non-PD (n = 43) peers completed the same baseline protocol. All MRI scans were processed with FreeSurfer and the FMRIB Software Library to analyze gray matter structures and frontal fractional anisotropy (FA) metrics. Processing speed, working memory, language, verbal memory, abstract reasoning, visuospatial, and motor functions were examined using reliable change methods.

RESULTS

At baseline, MN had striatal volume and frontal lobe thickness asymmetry relative to peers with mild prefrontal white matter FA asymmetry. Over time only MN's right caudate nucleus showed accelerated atrophy. Cognitively, MN had slowed psychomotor speed and visuospatial-linked deficits with mild visuospatial working memory declines longitudinally.

CONCLUSIONS

This is a unique report using normative neuroimaging and neuropsychology to describe an individual diagnosed with PD who had striking striatal asymmetry followed secondarily by cortical thickness asymmetry and possible frontal white matter asymmetry. His decline and variability in visual working memory could be linked to ongoing atrophy of his right caudate nucleus.

The cortical signature of symptom laterality in Parkinson's disease

Patients with Parkinson's disease (PD) often present with unilateral motor symptoms that eventually spread to the other side. This symptom lateralization is diagnostically important, as it serves to distinguish PD from other motor disorders with overlapping symptom profiles. Further, recent studies have shown that the side of symptom onset is important for prognosis, as there are differences in the rate of disease progression and the incidence of secondary symptoms between right- and left-dominant (RD, LD) patients. Physiologically, previous studies have shown asymmetrical decline in structure and metabolism throughout the basal ganglia, although connecting this directly to motor function has been difficult. To identify the neurophysiological basis of symptom laterality in PD, we recorded magnetoencephalography (MEG) during left- and right-hand movement paradigms in patients with PD who exhibited either RD or LD symptomatology. The beta oscillations serving these movements were then imaged using beamforming methods, and we extracted the time series of the peak voxel in the left and right primary motor cortices for each movement. In addition, each patient's symptom asymmetry was quantitated using the Unified Parkinson's Disease Rating Scale (UPDRS), which allowed the relationship between symptom asymmetry and neural asymmetry to be assessed. We found that LD patients had stronger beta suppression during movement, as well as greater post-movement beta rebound compared to patients with RD symptoms, independent of the hand that was moved. Interestingly, the asymmetry of beta activity during right-hand movement uniquely correlated with symptom asymmetry, such that the more LD the symptom profile, the more left-lateralized (i.e., contralateral to movement) the beta response; conversely, the more RD the symptom profile, the more right-lateralized (i.e., ipsilateral to movement) the beta response. This study is the first to directly probe the relationship between symptom asymmetry and the laterality of neural activity during movement in patients with PD, and suggests that LD patients have a fundamentally different and more “healthy” oscillatory pattern relative to RD patients.

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Right-dominant expression of Parkinson's has been connected to faster progression.

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Linkage between symptom asymmetry and cortical physiology remains unknown.

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Cortical motor activity was measured in patients with left/right-dominant symptoms.

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Patients with left-dominant symptoms had “healthier” pattern of motor responses.

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Laterality of cortical activity during movement was related to symptom laterality.

Side-of-onset of Parkinson's disease in relation to neuropsychological measures

BACKGROUND

Parkinson's disease (PD) usually emerges with a unilateral side-of-onset (left-onset: LOPD; right-onset: ROPD; Marinus & van Hilten, 2015) due to an asymmetrical degeneration of striatal dopaminergic neurons (Donnemiller et al., Brain, 135, 2012, 3348). This has led to a body of research exploring the cognitive, neuropsychological, and clinical differences between LOPD and ROPD (e.g., Verreyt et al., Neuropsychology Review, 21, 2011, 405).

METHODS

Thirty ROPD and 14 LOPD cases were drawn from a Boston clinic specializing in PD. Various cognitive and neuropsychological measures were used in an attempt to discover if there were indeed any differences between LOPD and ROPD in this cohort.

RESULTS

For LOPD, duration of illness was found to be significantly greater than that of ROPD. However, further testing was able to confirm that despite this difference, it was not the cause of the other significant differences found. Furthermore, this increased duration was consistent with a previous study (Munhoz et al., Parkinsonism and Related Disorders, 19, 2013, 77). Performance on the Digit Span Backward (DSB) was found to be significantly poorer in LOPD than ROPD, suggesting compromised executive function in LOPD. Additionally, LOPD had significantly greater anxiety on the DASS Anxiety scales than ROPD. However, unlike Foster et al (Cognitive and Behavioral Neurology, 23, 2010, 4), this increased anxiety could not account for the poorer performance on the DSB for LOPD. Finally, ROPD had significantly greater magical ideation than LOPD, which can be explained by the theory put forth by Brugger and Graves (European Archives of Psychiatry, 247, 1997, 55).

CONCLUSION

Clear and significant differences between LOPD and ROPD were found within our cohort. LOPD showed greater impairment of working memory, greater anxiety, and greater duration of illness-all independent of one another; whereas, those with ROPD had greater magical ideation, also independent of any other variables.

Tracking Parkinson's: Study Design and Baseline Patient Data

Background:

There is wide variation in the phenotypic expression of Parkinson’s disease (PD), which is driven by both genetic and epidemiological influences.

Objectives:

To define and explain variation in the clinical phenotype of PD, in relation to genotypic variation.

Methods:

Tracking Parkinson’s is a multicentre prospective longitudinal epidemiologic and biomarker study of PD. Patients attending specialist clinics in the United Kingdom with recent onset (<3.5 years) and young onset (diagnosed <50 years of age) PD were enrolled. Motor, non-motor and quality of life assessments were performed using validated scales. Cases are followed up 6 monthly up to 4.5 years for recent onset PD, and up to 1 year for young onset PD. We present here baseline clinical data from this large and demographically representative cohort.

Results:

2247 PD cases were recruited (1987 recent onset, 260 young onset). Recent onset cases had a mean (standard deviation, SD) age of 67.6 years (9.3) at study entry, 65.7% males, with disease duration 1.3 years (0.9), MDS-UPDRS 3 scores 22.9 (12.3), LEDD 295 mg/day (211) and PDQ-8 score 5.9 (4.8). Young onset cases were 53.5 years old (7.8) at study entry, 66.9% male, with disease duration 10.2 years (6.7), MDS-UPDRS 3 scores 27.4 (15.3), LEDD 926 mg/day (567) and PDQ-8 score 11.6 (6.1).

Conclusions:

We have established a large clinical PD cohort, consisting of young onset and recent onset cases, which is designed to evaluate variation in clinical expression, in relation to genetic influences, and which offers a platform for future imaging and biomarker research.

Does Side of Onset Influence the Pattern of Cerebral Atrophy in Parkinson's Disease?

Background

Imaging studies have revealed widespread neurodegeneration in Parkinson’s disease (PD), but only a few considered the issue of asymmetrical clinical presentations.

Objective

To investigate if the side of onset influences the pattern of gray matter (GM) atrophy in PD.

Methods

Sixty patients (57.87 ± 10.27 years) diagnosed with idiopathic PD according to the U.K. Brain Bank criteria, 26 with right-sided disease onset (RDO) and 34 with left-sided disease onset (LDO), were compared to 80 healthy controls (HC) (57.1 ± 9.47 years). We acquired T1-weighted images on a 3 T scanner. Images were processed and analyzed with VBM8 (SPM8/Dartel) on Matlab R2012b platform. Statistic assessments included a two-sample test (family-wise error p < 0.05) with extent threshold of 20 voxels.

Results

Compared to HC, LDO patients had GM atrophy in the insula, putamen, anterior cingulate, frontotemporal cortex, and right caudate, while the RDO group showed atrophy at the anterior cingulate, insula, frontotemporal, and occipital cortex.

Conclusion

This study revealed widespread GM atrophy in PD, predominantly in the left hemisphere, regardless of the side of onset. Future investigations should also consider handedness and side of onset to better characterize cerebral involvement and its progression in PD.

PARKINSON'S DISEASE PATIENTS WITH DOMINANT HEMIBODY AFFECTED BY THE DISEASE RELY MORE ON VISION TO MAINTAIN UPRIGHT POSTURAL CONTROL

This study assesses the association between disease onset side (dominant or non-dominant) and vision on postural control of Parkinson's disease patients. Patient volunteers composed two groups, according to the onset side affected: Dominant group (n=9; M age=66.1 yr., SD=7.2; 6 women, 3 men) and Non-dominant group (n=9; M age=67.4 yr., SD=6.4; 6 women, 3 men). The groups' postural control was assessed by posturography during quiet upright stance in two conditions, Eyes open and Eyes closed. Two-way analyses of variance (ANOVAs; group×condition) with repeated measures for the second factor assessed the differences associated with affected hemibody and vision on postural control. Analyses indicated that patients with the dominant side affected also presented significantly greater variation in center of pressure than those with the non-dominant side affected, mainly in the Eyes closed condition. The results demonstrate a higher reliance on vision in the dominant side, possibly to compensate somatosensory system impairments. These results also highlight the importance of analyzing the hemibody affected by the disease when postural control is assessed in this population.

Interactions of visual hallucinations, rapid eye movement sleep behavior disorder and cognitive impairment in Parkinson's disease: A review

Patients with Parkinson's disease may develop various non-motor symptoms during the course of the illness. Visual hallucinations (VH) and cognitive impairment (CI) are two common non-motor symptoms of Parkinson's disease. Studies have reported association of both VH and CI with presence of rapid eye movement sleep behavior disorder (RBD). Presence of visual hallucinations and cognitive impairment has been described as risk factors for emergence of each other. There is marked overlap in the risk factors for development of RBD, VH and CI in patients with PD. Results of clinical and epidemiological studies as well as studies based on neuroimaging, electrophysiology especially transcranial magnetic stimulation and neuropsycholgical evaluations in PD patients have suggested presence of certain common neurobiological process leading to emergence of RBD, VH and CI. Structural neuroimaging studies using voxel-based morphometry have often reported grey matter atrophy of hippocampus and parahippocampal cortices in PD patients with RBD, VH and CI. Cholinergic dysfunction is common in PD patients with RBD, VH and CI. This review explores the complex interactions of RBD, VH and CI in patients with PD and their potential implications.

Classification of symptom-side predominance in idiopathic Parkinson's disease

Asymmetry of symptom onset in Parkinson’s disease (PD) is strongly linked to differential diagnosis, progression of disease, and clinical manifestation, suggesting its importance in terms of specifying a therapeutic strategy for each individual patient. To scrutinize the predictive value of this consequential clinical phenomenon as a neuromarker supporting a personalized therapeutic approach, we modeled symptom-side predominance at disease onset based on brain morphology assessed with magnetic resonance (MR) images by utilizing machine learning classification. The integration of multimodal MR imaging data into a multivariate statistical model led to predict left- and right-sided symptom onset with an above-chance accuracy of 96%. By absolute numbers, all but one patient were correctly classified. Interestingly, mainly hippocampal morphology supports this prediction. Considering a different disease formation of this single outlier and the strikingly high classification, this approach proves a reliable predictive model for symptom-side diagnostics in PD. In brief, this work hints toward individualized disease-modifying therapies rather than symptom-alleviating treatments.

Influence of Dopaminergic Medication on Conditioned Pain Modulation in Parkinson's Disease Patients

Background

Pain is highly prevalent in patients with Parkinson’s disease (PD), but little is known about the underlying pathophysiological mechanisms. The susceptibility to pain is known to depend on ascending and descending pathways. Because parts of the descending pain inhibitory system involve dopaminergic pathways, dysregulations in dopaminergic transmission might contribute to altered pain processing in PD. Deficits in endogenous pain inhibition can be assessed using conditioned pain modulation (CPM) paradigms.

Methods

Applying such a paradigm, we investigated i) whether CPM responses differ between PD patients and healthy controls, ii) whether they are influenced by dopaminergic medication and iii) whether there are effects of disease-specific factors. 25 patients with idiopathic PD and 30 healthy age- and gender-matched controls underwent an established CPM paradigm combining heat pain test stimuli at the forearm and the cold pressor task on the contralateral foot as the conditioning stimulus. PD patients were tested under dopaminergic medication and after at least 12 hours of medication withdrawal.

Results

No significant differences between CPM responses of PD patients and healthy controls or between PD patients “on” and “off” medication were found. These findings suggest (i) that CPM is insensitive to dopaminergic modulations and (ii) that PD is not related to general deficits in descending pain inhibition beyond the known age-related decline. However, at a trend level, we found differences between PD subtypes (akinetic-rigid, tremor-dominant, mixed) with the strongest impairment of pain inhibition in the akinetic-rigid subtype.

Conclusions

There were no significant differences between CPM responses of patients compared to healthy controls or between patients “on” and “off” medication. Differences between PD subtypes at a trend level point towards different pathophysiological mechanisms underlying the three PD subtypes which warrant further investigation and potentially differential therapeutic strategies in the future.

Prevalence and correlates of sleep disorders in Parkinson's disease: a polysomnographic study

OBJECTIVE

Sleep disorders in Parkinson's disease are very common. Polysomnography (PSG) is considered the gold standard for diagnosis. The aim of the present study is to assess the prevalence of nocturnal sleep disorders diagnosed by polysomnography and to determine the associated clinical factors.

METHOD

A total of 120 patients with Parkinson's disease were included. All patients underwent a standardized overnight, single night polysomnography.

RESULTS

Ninety-four (78.3%) patients had an abnormal PSG. Half of the patients fulfilled criteria for sleep apnea-hypopnea syndrome (SAHS); rapid eye movement behavior disorder (RBD) was present in 37.5%. Characteristics associated with SAHS were age (p = 0.049) and body mass index (p = 0.016). Regarding RBD, age (p < 0.001), left motor onset (p = 0.047) and levodopa equivalent dose (p = 0.002) were the main predictors.

CONCLUSION

SAHS and RBD were the most frequent sleep disorders. Higher levodopa equivalent dose and body mass index appear to be risk factors for RBD and SAHS, respectively.

Revisiting the impact of REM sleep behavior disorder on motor progression in Parkinson's disease

BACKGROUND

Estimation of progression in Parkinson's disease (PD) is useful to guide clinical decisions and to enable patients to plan and manage their life with PD. Rapid eye movement (REM) sleep behavior disorder (RBD) and REM sleep without atonia (RWA) are recognized as early harbingers of neurodegeneration and may precede motor symptoms by years. However, their impact on motor progression remains elusive.

METHODS

We retrospectively analyzed polysomnographic and clinical data of 59 PD patients, grouping them into patients with RBD (n = 15), RWA (n = 22) and those with normal muscle atonia (n = 22). We compared the three groups with regard to motor progression, defined as changes in Unified Parkinson's Disease Rating Scale (UPDRS) III values per year, and selected PD specific characteristics.

RESULTS

Motor disability at first visit and time interval between first and last visits were similar between groups. We observed a significantly faster motor progression in PD patients with RBD and RWA than in those with preserved REM sleep atonia.

CONCLUSION

Our findings suggest that impaired muscle atonia during REM sleep might represent a marker of faster motor progression in PD.

Neural and behavioral substrates of subtypes of Parkinson's disease

Parkinson’s disease (PD) is a neurological disorder, associated with rigidity, bradykinesia, and resting tremor, among other motor symptoms. In addition, patients with PD also show cognitive and psychiatric dysfunction, including dementia, mild cognitive impairment (MCI), depression, hallucinations, among others. Interestingly, the occurrence of these symptoms—motor, cognitive, and psychiatric—vary among individuals, such that a subgroup of PD patients might show some of the symptoms, but another subgroup does not. This has prompted neurologists and scientists to subtype PD patients depending on the severity of symptoms they show. Neural studies have also mapped different motor, cognitive, and psychiatric symptoms in PD to different brain networks. In this review, we discuss the neural and behavioral substrates of most common subtypes of PD patients, that are related to the occurrence of: (a) resting tremor (vs. nontremor-dominant); (b) MCI; (c) dementia; (d) impulse control disorders (ICD); (e) depression; and/or (f) hallucinations. We end by discussing the relationship among subtypes of PD subgroups, and the relationship among motor, cognitive, psychiatric factors in PD.