Neuroimaging markers of motor and nonmotor features of Parkinson's disease: an 18f fluorodeoxyglucose positron emission computed tomography study

Neuroimaging of major depression in Parkinson's disease: Cortical thickness, cortical and subcortical volume, and spectroscopy findings

Depression is the most common psychiatric disorder in Parkinson's disease (PD). The aim of this study was to compare PD patients with current Major Depressive Disorder (MDD), lifetime MDD, and no MDD using three neuroimaging techniques. A total of 43 PD patients were selected and divided into three groups: (i) current MDD (n = 15), (ii) previous MDD without current MDD (n = 10); and (iii) control group (no current or lifetime MDD; n = 18). All participants underwent magnetic resonance imaging to evaluate cortical thickness, cortical and subcortical volume, and spectroscopy in the bilateral putamen and cingulate cortex. Volumetric analysis showed volume decreases in frontal and temporal areas, bilateral amygdala, and left cerebellar white matter in the lifetime MDD group compared to the control group. Furthermore, the volumes of the anterior cingulate cortex, right amygdala, and left cerebellar white matter were smaller in the group with current MDD compared to the control group. Regarding cortical thickness, the left rostral anterior cingulate gyrus of the group with previous MDD was thinner compared to the control group. There was a weak negative correlation between the NAA/Cre ratio in the right putamen and depressive symptoms. The results suggested current and lifetime MDD have a negative impact on the neurodegenerative process of PD, with decreased volume and/or reduction of cortical thickness in temporal and frontal areas, anterior cingulate cortex, amygdala, and cerebellar white matter.

Imaging the Nonmotor Symptoms in Parkinson's Disease

Parkinson's disease is acknowledged to be a multisystem syndrome, manifesting as a result of multineuropeptide dysfunction, including dopaminergic, cholinergic, serotonergic, and noradrenergic deficits. This multisystem disorder ultimately leads to the presentation of a range of nonmotor symptoms, now appreciated to be an integral part of the disease-specific spectrum of symptoms, often preceding the diagnosis of motor Parkinson's disease. In this chapter, we review the dopaminergic and nondopaminergic basis of these symptoms by exploring the neuroimaging evidence based on several techniques including positron emission tomography, single-photon emission computed tomography molecular imaging, magnetic resonance imaging, functional magnetic resonance imaging, and diffusion tensor imaging. We discuss the role of these neuroimaging techniques in elucidating the underlying pathophysiology of NMS in Parkinson's disease.

Cerebral metabolic change in Parkinson's disease patients with anxiety: A FDG-PET study

OBJECT

To detect the cerebral metabolic bases of Parkinson's disease (PD) patients with anxiety.

METHODS

Totally 28 idiopathic PD patients without depression (17-item Hamilton Depression Rating Scale, HAMD score <14) were enrolled in our study. All subjects were classified into PD with anxiety (PD-A) (n=13) and PD without anxiety (PD-NA) (n=15) by cutoff score of 11 according to Hamilton Anxiety Rating Scale (HAMA). Besides, age- and gender- matched healthy controls (HCs) (n=15) were selected. A resting-state F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) scan was applied to estimate cerebral metabolic activity. All statistical analyses were performed using IBM SPSS Statistics V20.0.0 software, while statistical parametric mapping software (SPM) was used to analyze the FDG-PET images.

RESULTS

PD-A showed decreased glucose metabolism in the bilateral orbitofrontal cortex (OFC, BA10 and BA11) when compared with PD-NA. Significant decrease of cerebral glucose metabolism in the bilateral OFC, bilateral supplementary motor area (SMA, BA6), bilateral dorsal anterior cingulate cortex (dACC, BA32), right dorsolateral prefrontal cortex (dlPFC, BA9), right ventrolateral prefrontal cortex (vlPFC, BA44), right putamen and left caudatum was detected in PD-A compared with HCs. There was significant reduced glucose metabolism of the bilateral SMA in PD-NA when compared with HCs (uncorrected p<0.005).

CONCLUSION

The anxiety of PD was associated with the metabolic reductions of PFC and striatal areas. OFC, part of PFC, could be taken as a characteristic feature for anxiety in PD. This metabolic pattern suggested that deficits of prefrontostriatal pathways might affect anxiety mood in PD.

Rivastigmine as a Symptomatic Treatment for Apathy in Parkinson's Dementia Complex: New Aspects for This Riddle

Over 90% of PDD patients show at least one neuropsychiatric symptom (NPS); in the 60-70% two or more NPS are present. Their incidence is important in terms of prognosis and severity of pathology. However, among all NPS, apathy is often the most disturbing, associated with greater caregiver's burden. Similar to other NPS, apathy may be due to a dysfunction of the nigrostriatal pathway, even though, not all the PD patients become apathetic, indicating that apathy should not entirely be considered a dopamine-dependent syndrome, and in fact it might also be related to acetylcholine defects. Apathy has been treated in many ways, without sure benefits; among these, Rivastigmine may present benefic properties. We present a series of 48 patients, suffering from PDD, treated with Rivastigmine, and followed-up for one year; they have been devotedly studied for apathy, even though all the other NPS disorders have been registered. Rivastigmine did not have a prolonged benefic effect on apathy, in our work, on the contrary of what had been observed in the literature, probably due to the longer follow-up of our patients.

Neuropsychiatric symptoms in untreated Parkinson's disease

Neuropsychiatric and cognitive symptoms are common in Parkinson's disease (PD) and may precede and exceed motor symptoms as major factors impacting disease course and quality of life. Neuropsychiatric symptoms (NPS) in PD are various and are attributed to pathologic changes within multiple brain regions, to psychological stress, and to adverse effects of dopamine replacement therapy. Sleep disorders and mood symptoms such as apathy, depression, and anxiety may antedate the development of motor symptoms by years, while other NPS such as impulse control disorders, psychosis, and cognitive impairment are more common in later stages of the disease. Few studies report on NPS in the early, untreated phase of PD. We reviewed the current literature on NPS in PD with a focus on the early, drug-naive stages of PD. Among these early disease stages, premotor and early motor phases were separately addressed in our review, highlighting the underlying pathophysiological mechanisms as well as epidemiological characteristics, clinical features, risk factors, and available techniques of clinical assessment.

Pathology of behavior in PD: What is known and what is not?

Abnormal behavior in Parkinson's disease (PD) stems from a complex orchestration of impaired neural networks that result from PD-related neurodegeneration across multiple levels. Typically, cellular and tissue abnormalities generate neurochemical changes and disrupt specific regions of the brain, in turn creating impaired neural circuits and dysfunctional global networks. The objective of this chapter is to provide an overview of the array of pathological changes that have been linked to different behavioral symptoms of PD such as depression, anxiety, apathy, fatigue, impulse control disorders, psychosis, sleep disorders and dementia.

Neural Correlates for Apathy: Frontal-Prefrontal and Parietal Cortical- Subcortical Circuits

Apathy is an uncertain nosographical entity, which includes reduced motivation, abulia, decreased empathy, and lack of emotional involvement; it is an important and heavy-burden clinical condition which strongly impacts in everyday life events, affects the common daily living abilities, reduced the inner goal directed behavior, and gives the heaviest burden on caregivers. Is a quite common comorbidity of many neurological disease, However, there is no definite consensus on the role of apathy in clinical practice, no definite data on anatomical circuits involved in its development, and no definite instrument to detect it at bedside. As a general observation, the occurrence of apathy is connected to damage of prefrontal cortex (PFC) and basal ganglia; “emotional affective” apathy may be related to the orbitomedial PFC and ventral striatum; “cognitive apathy” may be associated with dysfunction of lateral PFC and dorsal caudate nuclei; deficit of “autoactivation” may be due to bilateral lesions of the internal portion of globus pallidus, bilateral paramedian thalamic lesions, or the dorsomedial portion of PFC. On the other hand, apathy severity has been connected to neurofibrillary tangles density in the anterior cingulate gyrus and to gray matter atrophy in the anterior cingulate (ACC) and in the left medial frontal cortex, confirmed by functional imaging studies. These neural networks are linked to projects, judjing and planning, execution and selection common actions, and through the basolateral amygdala and nucleus accumbens projects to the frontostriatal and to the dorsolateral prefrontal cortex. Therefore, an alteration of these circuitry caused a lack of insight, a reduction of decision-making strategies, and a reduced speedness in action decision, major responsible for apathy. Emergent role concerns also the parietal cortex, with its direct action motivation control. We will discuss the importance of these circuits in different pathologies, degenerative or vascular, acute or chronic.

Neural correlates of anxiety symptoms in mild Parkinson's disease: A prospective longitudinal voxel-based morphometry study

BACKGROUND

Anxiety is prevalent in patients with Parkinson's disease (PD) and may affect patients' quality of life. Yet, little is known about the neural basis of anxiety in PD, and none have used a longitudinal design.

METHODS

73 patients with mild PD were recruited and followed up for 18months. A whole-brain analysis was first used to identify brain regions associated with anxiety symptoms, followed by a regional analysis focusing on a priori hypothesised regions at baseline. A multivariate generalized estimating equations analysis was then conducted to determine the longitudinal association between grey matter (GM) volumetric changes of these significant regions and changes of anxiety symptoms.

RESULTS

At baseline, anxiety symptom severity was associated with decreased GM volumes in the bilateral precuneus and anterior cingulate cortex (ACC). Over 18months, increased severity of anxiety symptoms was associated with decreased GM volume in the left precuneus and ACC, independent of age, gender, education, depressive symptom severity or use of psychiatric medication.

CONCLUSIONS

These results mainly implicate the precuneus and ACC in the pathogenesis of anxiety in PD. We speculate that these structural changes could reflect the disrupted default mode network due to PD pathology, contributing to spontaneous anxiety-related self-focused thoughts.

Apathy and Impulse Control Disorders: Yin & Yang of Dopamine Dependent Behaviors

Neuropsychiatric symptoms are common non-motor symptoms in Parkinson's disease (PD). Apathy and impulse control disorders (ICD) are two opposite motivational expressions of a continuous behavioural spectrum involving hypo- and hyperdopaminergia. Both syndromes share pathological (decreased vs increased) dopamine receptor stimulation states. Apathy belongs to the spectrum of hypodopaminergic symptoms together with anhedonia, anxiety and depression. Apathy is a key symptom of PD which worsens with disease progression. Animal models, imaging and pharmacological studies concur in pointing out dopaminergic denervation in the aetiology of parkinsonian apathy with a cardinal role of decreased tonic D2/D3 receptor stimulation. ICDs are part of the hyperdopaminergic behavioural spectrum, which also includes punding, and dopamine dysregulation syndrome (DDS), which are all related to non-physiological dopaminergic stimulation induced by antiparkinsonian drugs. According to clinical data tonic D2/D3 receptor stimulation can be sufficient to induce ICDs. Clinical observations in drug addiction and PD as well as data from studies in dopamine depleted rodents provide hints allowing to argue that both pulsatile D1 and D2 receptor stimulation and the severity of dopaminergic denervation are risk factors to develop punding behavior and DDS. Imaging studies have shown that the brain structures involved in drug addiction are also involved in hyperdopaminergic behaviours with increase of bottom-up appetitive drive and decrease in prefrontal top down behavioural control.

Pathophysiology of Motor Dysfunction in Parkinson's Disease as the Rationale for Drug Treatment and Rehabilitation

Cardinal motor features of Parkinson's disease (PD) include bradykinesia, rest tremor, and rigidity, which appear in the early stages of the disease and largely depend on dopaminergic nigrostriatal denervation. Intermediate and advanced PD stages are characterized by motor fluctuations and dyskinesia, which depend on complex mechanisms secondary to severe nigrostriatal loss and to the problems related to oral levodopa absorption, and motor and nonmotor symptoms and signs that are secondary to marked dopaminergic loss and multisystem neurodegeneration with damage to nondopaminergic pathways. Nondopaminergic dysfunction results in motor problems, including posture, balance and gait disturbances, and fatigue, and nonmotor problems, encompassing depression, apathy, cognitive impairment, sleep disturbances, pain, and autonomic dysfunction. There are a number of symptomatic drugs for PD motor signs, but the pharmacological resources for nonmotor signs and symptoms are limited, and rehabilitation may contribute to their treatment. The present review will focus on classical notions and recent insights into the neuropathology, neuropharmacology, and neurophysiology of motor dysfunction of PD. These pieces of information represent the basis for the pharmacological, neurosurgical, and rehabilitative approaches to PD.

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.

Position Emission Tomography/Single-Photon Emission Tomography Neuroimaging for Detection of Premotor Parkinson's Disease

Premotor Parkinson's disease (PD) refers to a prodromal stage of Parkinson's disease (PD) during which nonmotor clinical features may be present. Currently, it is difficult to make an early diagnosis for premotor PD. Molecular imaging with position emission tomography (PET) or single-photon emission tomography (SPECT) offers a wide variety of tools for overcoming this difficulty. Indeed, molecular imaging techniques may play a crucial role in diagnosing, monitoring and evaluating the individuals with the risk for PD. For example, dopaminergic dysfunctions can be identified by detecting the expression of vesicular monoamine transporter (VMAT2) and aromatic amino acid decarboxylase (AADC) to evaluate the conditions of dopaminergic terminals functions in high-risk individuals of PD. This detection provides a sensitive and specific measurement of nonmotor symptoms (NMS) such as olfactory dysfunction, sleep disorders, and psychiatric symptoms in the high-risk patients, especially at the premotor phase. Molecular imaging technique is capable of detecting the dysfunction of serotonergic, noradrenergic, and cholinergic systems that are typically associated with premotor manifestations. This review discusses the importance of SPECT/PET applications in the detection of premotor markers preceding motor abnormalities with highlighting their great potential for early and accurate diagnosis of premotor symptoms of PD and its scientific significance.

[Neuroimaging of functional abnormalities in apathy]

Apathy is a common comorbid condition in neurologic and somatic disorders (Alzheimer's disease, Parkinson's disease, multiple sclerosis, frontotemporal dementia, senile dementia, HIV) and a symptom of many psychiatric disorders. Neurophysiologic research in this area aims to examine the specific features to differentiate the apathy from main disorder. This paper reviews neuroimaging studies of functional abnormalities in apathy.

Apathy in Parkinson's disease: clinical features, neural substrates, diagnosis, and treatment

Normal maintenance of human motivation depends on the integrity of subcortical structures that link the prefrontal cortex with the limbic system. Structural and functional disruption of different networks within these circuits alters the maintenance of spontaneous mental activity and the capacity of affected individuals to associate emotions with complex stimuli. The clinical manifestations of these changes include a continuum of abnormalities in goal-oriented behaviours known as apathy. Apathy is highly prevalent in Parkinson's disease (and across many neurodegenerative disorders) and can severely affect the quality of life of both patients and caregivers. Differentiation of apathy from depression, and discrimination of its cognitive, emotional, and auto-activation components could guide an individualised approach to the treatment of symptoms. The opportunity to manipulate dopaminergic treatment in Parkinson's disease allows researchers to study a continuous range of motivational states, from apathy to impulse control disorders. Parkinson's disease can thus be viewed as a model that provides insight into the neural substrates of apathy.

Early diagnosis of Alzheimer's disease and Parkinson's disease associated with dementia using cerebral perfusion SPECT

BACKGROUND

Since patterns of cognitive dysfunction in mild Parkinson's disease associated with dementia (PDD) are similar to those in mild Alzheimer's disease (AD), it is difficult to accurately differentiate between these two types of dementia in their early phases using neuropsychological tests. The purpose of the current study was to investigate differences in cerebral perfusion patterns of patients with AD and PDD at the earliest stages using single photon emission computed tomography (SPECT).

METHODS

We consecutively recruited 31 patients with mild PDD, 32 patients with mild probable AD and 33 age-matched healthy subjects. All subjects underwent (99m)Tc-hexamethylpropyleneamine oxime perfusion SPECT and completed general neuropsychological tests.

RESULTS

We found that both mild PDD and AD patients showed distinct hypoperfusion in frontal, parietal and temporal regions, compared with healthy subjects. More importantly, hypoperfusion in occipital and cerebellar regions was observed only in mild PDD.

CONCLUSION

The observation of a significant decrease in cerebral perfusion in occipital and cerebellar regions in patients with mild PDD is likely useful to differentiate between PDD and AD at the earliest stages.

Diagnoses behind patients with hard-to-classify tremor and normal DaT-SPECT: a clinical follow up study

The [¹²³I]ioflupane—a dopamine transporter radioligand—SPECT (DaT-SPECT) has proven to be useful in the differential diagnosis of tremor. Here, we investigate the diagnoses behind patients with hard-to-classify tremor and normal DaT-SPECT. Therefore, 30 patients with tremor and normal DaT-SPECT were followed up for 2 years. In 18 cases we were able to make a diagnosis. The residual 12 patients underwent a second DaT-SPECT, were then followed for additional 12 months and thereafter the diagnosis was reconsidered again. The final diagnoses included cases of essential tremor, dystonic tremor, multisystem atrophy, vascular parkinsonism, progressive supranuclear palsy, corticobasal degeneration, fragile X–associated tremor ataxia syndrome, psychogenic parkinsonism, iatrogenic parkinsonism and Parkinson's disease. However, for 6 patients the diagnosis remained uncertain. Larger series are needed to better establish the relative frequency of the different conditions behind these cases.

Examining the relationship between head trauma and neurodegenerative disease: A review of epidemiology, pathology and neuroimaging techniques

Traumatic brain injuries (TBI) are induced by sudden acceleration-deceleration and/or rotational forces acting on the brain. Diffuse axonal injury (DAI) has been identified as one of the chief underlying causes of morbidity and mortality in head trauma incidents. DAIs refer to microscopic white matter (WM) injuries as a result of shearing forces that induce pathological and anatomical changes within the brain, which potentially contribute to significant impairments later in life. These microscopic injuries are often unidentifiable by the conventional computed tomography (CT) and magnetic resonance (MR) scans employed by emergency departments to initially assess head trauma patients and, as a result, TBIs are incredibly difficult to diagnose. The impairments associated with TBI may be caused by secondary mechanisms that are initiated at the moment of injury, but often have delayed clinical presentations that are difficult to assess due to the initial misdiagnosis. As a result, the true consequences of these head injuries may go unnoticed at the time of injury and for many years thereafter. The purpose of this review is to investigate these consequences of TBI and their potential link to neurodegenerative disease (ND). This review will summarize the current epidemiological findings, the pathological similarities, and new neuroimaging techniques that may help delineate the relationship between TBI and ND. Lastly, this review will discuss future directions and propose new methods to overcome the limitations that are currently impeding research progress. It is imperative that improved techniques are developed to adequately and retrospectively assess TBI history in patients that may have been previously undiagnosed in order to increase the validity and reliability across future epidemiological studies. The authors introduce a new surveillance tool (Retrospective Screening of Traumatic Brain Injury Questionnaire, RESTBI) to address this concern.

Predictors of mild cognitive impairment in early-stage Parkinson's disease

Aim

The aim of this study was to identify mild cognitive deficits in Parkinson's disease (PD) prior to extensive neurodegeneration and to evaluate the extent to which dopamine depletion and other disease-related predictors can explain cognitive profiles.

Methods

Neuropsychological performances of 40 nondemented early-stage PD patients and 42 healthy controls were compared across on or off dopaminergic medications. Stepwise regression evaluated cognitive predictors of early-stage PD and disease-related predictors of PD cognition (levodopa dose, disease duration, Unified Parkinson's Disease Rating Scale score, sleep, quality of life, and mood) across on and off states.

Results

Neuropsychological performance was lower in PD patients across cognitive domains with significant memory, naming, visuomotor, and complex attention/executive deficits, but with intact visuospatial, simple attention, and phonemic fluency functions. However, medication effects were absent except for simple attention. Regression analyses revealed age, working memory, and memory recall to be the best cognitive predictors of PD, while age, quality of life, disease duration, and anxiety predicted PD cognition in the off state.

Conclusion

Nondemented early-stage PD patients presented with extensive mild cognitive deficits including prominent memory impairment. The profile was inconsistent with expected isolated frontostriatal dysfunction previously attributed to dopamine depletion and this highlights the need to further characterize extranigral sources of mild cognitive impairment in PD.