Progress in clinical neurosciences: Parkinson's disease with dementia and dementia with Lewy bodies

Wearable technological platform for multidomain diagnostic and exercise interventions in Parkinson's disease

Physical activity and exercise have become a central component of medical management of chronic illness, particular for the elderly who suffer from neurodegenerative disorders that impair their cognition and mobility. This chapter summarizes our recent research showing that a new generation of wearable technology can be adopted as diagnostic and rehabilitation tools for people living with Parkinson's disease. For example, wearable device-enabled 6-min walking test can be automated to eliminate human supervision and many other technical factors that confound the results with conventional testing. With reduced cost and increased test standardization, the technology can be adopted for population-based screening of cardiovascular fitness and gait rehabilitation training efficacy associated with many medical conditions. The Ambulosono platform for multidomain exercise intervention, in particular, has the potential to deliver lasting clinical benefits in slowing PD progression. The platform, through the integration of brisk walking with behavioral shaping strategies such as contingency reinforcement, anticipatory motor control and musical motivational stimulation, creates a home exercise regime that can transform monotonous walking into a pleasurable daily activity and habit.

Clinical Trials in Parkinson's Disease Dementia and Dementia with Lewy Bodies

Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are pathological overlapping and important causes of dementia for which clinical trials are in their infancy. Cholinesterase inhibitors may be of benefit in DLB and PDD, as suggested by placebo-controlled clinical trials of rivastigmine and donepezil. The anti-psychotic agent clozapine has been of benefit in PD and PDD, but other agents, such as quetiapine, require adequate assessment. Barriers to trials include pathological overlap that can lead to inaccuracies in clinical diagnosis, unavailability of a consensus definition for PDD, unanswered questions regarding natural history and the paucity of validated outcome measures. Motor impairment must be considered in patients with PDD and DLB; conversely, cognitive impairment should be assessed in trials targeting motor impairment in advanced PD. Potential targets for treatment include onset of dementia, cognitive impairment, behavioral impairment, functional decline, falls, nursing home placement, mortality, quality of life and economic impact. Biomarkers including neuroimaging and cerebrospinal fluid markers are not currently established. At present PDD and DLB are distinct entities by definition. Future studies, including clinical trials and biomarker studies, will help to further define the clinical and therapeutic implications of this distinction.

Corpus Callosum and Cingulum Tractography in Parkinson's Disease

Background:

In Parkinson's disease (PD) cell loss in the substantia nigra is known to result in motor symptoms; however widespread pathological changes occur and may be associated with non-motor symptoms such as cognitive impairment. Diffusion tensor imaging is a quantitative imaging method sensitive to the micro-structure of white matter tracts.

Objective:

To measure fractional anisotropy (FA) and mean diffusivity (MD) values in the corpus callosum and cingulum pathways, defined by diffusion tensor tractography, in patients with PD, PD with dementia (PDD) and controls and to determine if these measures correlate with Mini-Mental Status Examination (MMSE) scores in parkinsonian patients.

Methods:

Patients with PD (17 Males [M], 12 Females [F]), mild PDD (5 M, 1F) and controls (8 M, 7F) underwent cognitive testing and MRI scans. The corpus callosum was divided into four regions and the cingulum into two regions bilaterally to define tracts using the program DTIstudio (Johns Hopkins University) using the fiber assignment by continuous tracking algorithm. Volumetric MRI scans were used to measure white and gray matter volumes.

Results:

Groups did not differ in age or education. There were no overall FA or MD differences between groups in either the corpus callosum or cingulum pathways. In PD subjects the MMSE score correlated with MD within the corpus callosum. These findings were independent of age, sex and total white matter volume.

Conclusions:

The data suggest that the corpus callosum or its cortical connections are associated with cognitive impairment in PD patients.

Alzheimer's disease: Seeing the signs early

PURPOSE

Many patients with early symptoms of Alzheimer's disease (AD) first seek help from their primary care providers (PCPs). PCPs must therefore be watchful for signs and symptoms of AD, and should screen elderly patients who complain of memory and cognitive problems for dementia.

DATA SOURCES

Published literature on case detection, diagnosis, and treatment of AD.

CONCLUSIONS

There are a number of simple, accurate, and fast tools to facilitate case detection, including the Mini-Mental State Examination. Once a diagnosis has been made, healthcare providers, patients, and caregivers can evaluate treatment options. Several medications are available for symptomatic treatment of AD, including the cholinesterase inhibitors donepezil, galantamine, and rivastigmine, and for later stage disease, the N-methyl D-aspartate (NMDA) receptor antagonist, memantine.

IMPLICATIONS FOR PRACTICE

Early intervention is critical because a delay in treatment is associated with nonreversible symptom progression. Realistic treatment expectations include reduction in symptom severity and slowed decline in cognition, function, and behavior. Treatment may allow patients to retain independence longer and reduce the burden that advanced AD places on caregivers.

Cholinesterase inhibitors in Alzheimer's disease and Lewy body spectrum disorders: the emerging pharmacogenetic story

This review provides an update on the current state of pharmacogenetic research in the treatment of Alzheimer's disease (AD) and Lewy body disease (LBD) as it pertains to the use of cholinesterase inhibitors (ChEI). AD and LBD are first reviewed from clinical and pathophysiological perspectives. This is followed by a discussion of ChEIs used in the symptomatic treatment of these conditions, focusing on their unique and overlapping pharmacokinetic and pharmacodynamic profiles, which can be used to identify candidate genes for pharmacogenetics studies. The literature published to date is then reviewed and limitations are discussed. This is followed by a discussion of potential endophenotypes which may help to refine future pharmacogenetic studies of response and adverse effects to ChEIs.

Sharpening the boundaries of Parkinson-associated dementia: recommendation for a neuropsychological diagnostic procedure

Older adults suffering from Parkinson's disease (PD) frequently present with an additional form of severe neurodegenerative and/or vascular pathology. Findings of differential clinical manifestations of cognitive impairment, depending on presence and nature of such coexisting brain pathology, raise the question for neuropsychological procedures that are capable not only of distinguishing between non-demented PD patients and patients with Parkinson-associated dementia (PDD), but also of detecting other types of cognitive decline, most likely Alzheimer's disease (AD) or vascular dementia (VD), superimposing PD. The aim of this article is to review the literature on neuropsychological processes at risk in developing PDD, to introduce comorbid causes of cognitive decline in the presence of PD, to discuss the scope of the "cortical versus subcortical dementia"-concept in view of its capability of differentiating dementias, and to scrutinize existing diagnostic criteria concerning the toleration of comorbidity. Additionally, we derive an evidence-based neuropsychological diagnostic procedure for assessing PDD under special consideration of these comorbid aspects.

MRI confirms mild cognitive impairments prodromal for Alzheimer's, vascular and Parkinson-Lewy body dementias

OBJECTIVES

MRI assessments were correlated with serial Combined Mini-Mental Cognitive Capacity Screening Examinations (CMC). Vascular-MCI (VMCI), Neurodegenerative MCI (NMCI) and Parkinson-Lewy body MCI (PLB-MCI) were compared during conversions to dementia. Mild cognitive impairments (MCI) are identifiable prodromes for all dementia subtypes. MRI abnormalities are characterized among MCI subjects prodromal for dementia of Alzheimer's disease (DAT), vascular dementia (VaD) and Parkinson-Lewy body dementia (PLBD).

METHODS

Aging volunteers (n=166) were recruited from ongoing longitudinal studies of aging, stroke, cerebrovascular disease and dementia. Cognitively normal (CN, n=52), MCIs of neurodegenerative (N-MCI, n=30), vascular (V-MCI, n=35) and Parkinson-Lewy Body (PLB-MCI, n=8) subtypes, plus converted DAT (n=19), VaD (n=17) and PLBD (n=5) were all diagnosed according to established protocol recommendations. Cerebral MRI abnormalities were likewise intercorrelated utilizing quantitative volumetric measurements.

RESULTS

V-MCI and converted VaD showed extensive leukoaraiosis with more lacunar infarcts than subjects with N-MCI or PLB-MCI. N-MCI, prodromal for DAT, showed medial temporal atrophy, greater enlargement of temporal horns, and fewer vascular lesions. PLB-MCI, prodromal for PLBD, displayed third ventricular enlargement greater than N-MCI and V-MCI, with similar but less severe atrophy of medial temporal lobe than N-MCI and fewer vascular lesions than V-MCI. Cognitive Impairments due to PLB with vascular features (V-PLB-CI) showed more lacunar and microvascular lesions involving both white matter and basal ganglia with greater frontal horn enlargement.

CONCLUSIONS

This study confirms different MCI subtypes prior to conversion to different dementias listed, recognizable by specific MRI abnormalities.

Rivastigmine: in Parkinson's disease dementia

Rivastigmine is a carbamate-type dual inhibitor of brain acetyl- and butyrylcholinesterases that has been evaluated in the symptomatic treatment of patients with mild to moderate dementia associated with idiopathic Parkinson's disease. Oral rivastigmine 3-12 mg/day for 24 weeks was significantly more effective than placebo in ameliorating cognitive and functional decline, including attentional deficits, in patients with Parkinson's disease dementia in a randomised, double-blind trial. The beneficial effects of rivastigmine observed in the double-blind trial were generally maintained in a 24-week extension of this study in which all patients received active treatment; placebo recipients who switched to rivastigmine also experienced improvements in their cognitive and functional symptoms at week 48. Rivastigmine appeared to be generally well tolerated, with the most common adverse events being mild to moderate in intensity and cholinergic in nature. Parkinsonian symptoms (mainly tremor) were more common in rivastigmine than placebo recipients.

Recognition and management of neuropsychiatric complications in Parkinson's disease

Parkinson's disease is primarily considered a motor disease characterized by rest tremor, rigidity, bradykinesia and postural disturbances. However, neuropsychiatric complications, including mood and anxiety disorders, fatigue, apathy, psychosis, cognitive impairment, dementia, sleep disorders and addictions, frequently complicate the course of the illness. The pathophysiologic features of these complications are multifaceted and include neuropathophysiologic changes of a degenerative disease, exposure to antiparkinsonian treatments and emotional reactions to having a disabling chronic illness. Changes in mental status have profound implications for the well-being of patients with Parkinson's disease and of their caregivers. Treatment is often efficacious but becomes a challenge in advanced stages of Parkinson's disease. In this article, we review the key clinical features of neuropsychiatric complications in Parkinson's disease as well as what is known about their epidemiologic characteristics, risk factors, pathophysiologic features and management.

Apolipoprotein E epsilon4 and catechol-O-methyltransferase alleles in autopsy-proven Parkinson's disease: relationship to dementia and hallucinations

We determined whether apolipoprotein E epsilon4 (ApoE4) or catechol-O-methyltransferase (COMT) genotypes were associated with dementia, hallucinations, Alzheimer's disease pathological findings (AP), or cortical Lewy bodies (CLBs) in autopsy-confirmed cases of Parkinson's disease (PD). Outcomes were obtained from medical records. Pathology reports identified AP and CLBs. Brain tissue was genotyped. A total of 47 subjects (33 men, 14 women) had PD onset at 62.4 +/- 8.7 years of age and died at 77.8 +/- 5.6 years of age. Demented and hallucinating patients did not differ in age at onset (AO) of PD or age at death, or the proportion ApoE4+, AP+, or CLB+ compared to nondemented patients or non-hallucinating patients. ApoE4 and COMT (low metabolizer [LH], intermediate metabolizer [HL], or high metabolizer [HH]) did not influence AO, death, or dementia- or hallucination-free survival, based on age or duration of treatment. All seven subjects with AP were demented and had hallucinations. CLBs were associated with dementia but not hallucinations. In Cox regression models adjusting for AO and duration of treatment, increased risk of dementia was associated with male sex but not significantly with ApoE4; inclusion of AP in the model did not affect the results; COMT was not a risk factor for dementia. Psychosis risk was not associated with ApoE4, COMT, or sex. The observation that males have increased dementia risk and the trend for ApoE4 requires confirmation in larger prospective autopsy studies.

A topological model of the interaction between alpha-synuclein and sodium dodecyl sulfate micelles

Human alpha-synuclein is a 140-amino acid protein of unknown function abundantly expressed in the brain and found in Lewy bodies, a characteristic feature of Parkinson's disease. Alpha-synuclein is random in water under physiological conditions, but the first approximately 100 residues interact with SDS micelles or acidic phospholipid small unilamellar vesicles and adopt an ordered conformation. The rest of the molecule remains disordered in the bulk of the solution. The conformation of the N-terminal portion of the molecule in lipids was described as an extended helix [Ramakrishnan, M., Jensen, P. H., and Marsh, D. (2003) Biochemistry 42, 12919-12926], as two distinct alpha-helices interrupted by a two-residue break [Chandra, S., Chen, X., Rizo, J., Jahn, R., and Sudhof, T. C. (2003) J. Biol. Chem. 278, 15313-15318], or as a noncanonical conformation, the alpha11/3 helix [Bussell, R., Jr., and Eliezer, D. (2003) J. Mol. Biol. 329, 763-778]. We characterized the topology of the different regions of alpha-synuclein relative to the surface of SDS micelles using spin probe-induced broadening of NMR signals, (15)N relaxation measurements, and fluorescence spectroscopy. Our results support the presence of two N-terminal helices, positioned on the surface of the micelle and separated by a flexible stretch. The region of residues 61-95 of the protein also adopts a helical conformation, but it is partially embedded in the micelle. These results could shed some light on the role of the membrane on the aggregation process of alpha-synuclein.