Demented PD Research Articles

Education-corrected CERAD identifies MCI and dementia in Parkinson's disease.

This study examined whether controlling for educational background in the CERAD cognitive screening battery would affect the likelihood of patients with Parkinson's disease to fulfill criteria for mild cognitive impairment (PD-MCI) and dementia (PDD). One-hundred seventeen patients with PD were studied. Cognitive impairment was determined as two subtest scores falling below either the standard cutoff scores or education-corrected cutoff scores. The presence of dementia was determined by clinical interview or Clinical Dementia Rating. Patients were then classified as PD-MCI and PDD according to cognitive test performance and presence/absence of dementia. The number of cognitively impaired patients (PD-MCI or PDD) was significantly higher when education-controlled cutoff scores were used (62.5% vs 38%). Correspondingly, the number of false negatives (demented PD patients performing normally in CERAD) was significantly lower when education-corrected cutoff scores were used (4% vs 10%). Controlling for education increases the sensitivity of the CERAD for PD-MCI and PDD.

Entorhinal cortex atrophy differentiates Parkinson's disease patients with and without dementia

Volumetric measures of mesial temporal lobe structures on MRI scans recently have been explored as potential biomarkers of dementia in patients with PD, with investigations primarily focused on hippocampal volume. Both in vivo MRI and postmortem tissue studies in Alzheimer's disease, however, demonstrate that the entorhinal cortex (ERC) is involved earlier in disease-related pathology than the hippocampus. The ERC, a region integral in declarative memory function, projects multimodal sensory information to the hippocampus through the perforant path. In PD, ERC atrophy, as measured on MRI, however, has received less attention, compared to hippocampal atrophy. We compared ERC and hippocampal atrophy in 12 subjects with PD dementia including memory impairment, 14 PD subjects with normal cognition, and 14 healthy controls with normal cognition using manual segmentation methods on MRI scans. Though hippocampal volumes were similar in the two PD cognitive groups, ERC volumes were substantially smaller in the demented PD subjects, compared to cognitively normal PD subjects (P < 0.05). In addition, normalized ERC and hippocampal volumes for right and left hemispheres were significantly lower in the demented PD group, compared to healthy controls. Our findings suggest that ERC atrophy differentiates demented and cognitively normal PD subjects, in contrast to hippocampal atrophy. Thus, ERC atrophy on MRI may be a potential biomarker for dementia in PD, particularly in the setting of memory impairment.

PDD‐Short Screen: A brief cognitive test for screening dementia in Parkinson's disease

The diagnosis of Parkinson's disease with dementia (PDD) is currently based on clinical criteria (DSM-IV, MDS-Task Force). In daily practice and research studies, these criteria still depend on the subjective impression of the examiner. Brief screening tests (BST) are helpful in identifying patients with PD with dementia, which can be difficult in patients with advanced PD. We aimed to develop a BST for PD, the PDD-Short Screen (PDD-SS), to accurately and quickly screen for PDD. In this prospective study, 70 patients with nondemented (age 73.8 +/- 4.4) and 32 demented (age 73.8 +/- 4.4) PD regularly attending a Movement Disorders Clinic were included. Diagnosis of dementia was based on DSM-IV criteria, CDR score >or=1, and PD-CRS total score <or=64. The PDD-SS, Mattis Dementia Rating Scale (MDRS), and Mini-Mental State Examination (MMSE) were administered to all participants. Validity, reliability, and discriminative power of the PDD-SS were examined. The final version of the scale included the items immediate and delayed verbal memory, clock drawing, alternating verbal fluency, and a questionnaire covering cognitive and psychiatric (hallucinations, apathy) symptoms common in PDD. A cutoff score <or=11 on the PDD-SS yielded high sensitivity (89.8%) and specificity (88.5%) for diagnosing PDD. The MDRS displayed similar accuracy, but the PDD-SS administration time was significantly shorter (4.8-6.9 vs. 17.5-25.2 minutes). Diagnosis of dementia using the PDD-SS was not influenced by age, education, or motor function. The PDD-SS appears as the first BST for diagnosing PDD, displays an excellent diagnostic accuracy, and takes 5 to 7 minutes to be administered.

APOE and the risk of PD with or without dementia in a population-based study.

To study the association between APOE genotype and PD with or without dementia. The study formed part of the Rotterdam Study, a prospective, population-based cohort study on the frequency, etiology, and prognosis of chronic diseases. The cohort examined for PD consisted of 6,969 independently living or institutionalized inhabitants from a suburb of Rotterdam, the Netherlands, aged 55 years or older. All participants were screened at baseline (1990 to 1993) and at follow-up (1993 to 1994) for symptoms of parkinsonism by study physicians; screen positives received a diagnostic workup by a neurologist. APOE genotyping was available for 107 PD patients (26 with and 81 without dementia) and 4,805 non-PD control subjects. The presence of at least one epsilon2 allele significantly increased the risk of PD (OR = 1.7; 95% CI, 1.0 to 2.8). When we looked separately for demented and nondemented PD patients as compared with nonparkinsonian controls, APOE did not appear to be associated with PD without dementia, but both the epsilon2 and the epsilon4 allele increased the risk of PD with dementia (OR = 5.6; 95% CI, 2.0 to 15.2 and OR = 3.6; 95% CI, 1.3 to 9.9). The risk of dementia for epsilon4 allele carriers was not significantly different for persons with or without PD. However, the epsilon2 allele strongly increased the risk of dementia in patients with PD (interaction p < 0.007). In the elderly the APOE-epsilon2 allele increases the risk of PD and, in particular, the risk of PD with dementia.

Risk of Alzheimer's disease in relatives of Parkinson's disease patients with and without dementia.

To determine whether first-degree relatives of PD patients with dementia were at increased risk for the development of AD compared with first-degree relatives of nondemented PD patients and nondemented normal subjects from the community. A structured family history interview was administered to 146 nondemented PD patients, 120 patients with PD and dementia, and 903 normal subjects from the community to ascertain the presence of AD among parents and siblings of these subjects. Cox proportional hazards models with double censoring techniques for missing information were used to model the risk of AD among relatives. No increase in risk of AD was found among parents of patients with PD and dementia or parents of nondemented PD patients compared with parents of normal subjects. However, siblings of demented PD patients were three times as likely (relative risk [RR] = 3.2, 95% confidence interval [CI] = 1.1 to 9.4, p < 0.04) as siblings of normal subjects to develop AD. When only siblings >65 years of age were considered, there was a fivefold increase in risk of AD among siblings of demented PD patients compared with siblings of normal subjects (RR = 4.9, 95% CI = 1.1 to 21.4, p < 0.03). The risk of AD was also increased for female relatives, regardless of whether the woman was a relative of a demented PD patient, a nondemented PD patient, or a normal subject. Ethnicity and APOE genotype did not affect dementia status among relatives. The increased risk of AD in siblings of demented PD patients compared with siblings of normal subjects supports the possibility of familial aggregation of AD and PD with dementia.

Basal ganglia disease and visuospatial cognition: Are there disease-specific impairments?

Visuospatial deficits in basal ganglia disease may be a non-specific function of the severity of dementia or they could reflect disease-specific impairments. To examine this question, Huntington (HD) patients, demented and non-demented Parkinson (PD) patients and healthy controls were examined with neuropsychological tests emphasising visuospatial abilities. Global intellectual function and general visuospatial cognition were less efficient in the two demented patient groups relative to both controls and non-demented PD patients and they did not differ significantly between non-demented Parkinsonians and controls nor between demented PD and HD patients. However, HD patients but not demented PD patients were impaired on a test of person-centred spatial judgement compared to non-demented subjects while demented PD patients scored significantly lower than HD patients on a test of field independence. Factor analysis yielded a factor reflecting general visuospatial processing capacity which discriminated between demented and non-demented PD patients but not between demented PD and HD patients. A unique factor associated with the manipulation of person-centred space discriminated between demented PD and HD patients. These results suggest general visuospatial processing is impaired as a non-specific function of dementia presence in HD and PD. Abnormalities in circumscribed aspects of visuospatial function, on the other hand, may differentiate between HD and PD, suggesting differential involvement of the basal ganglia in the respective illnesses.

Basal Ganglia Disease and Visuospatial Cognition: Are There Disease-Specific Impairments?

Visuospatial deficits in basal ganglia disease may be a non-specific function of the severity of dementia or they could reflect disease-specific impairments. To examine this question, Huntington (HD) patients, demented and non-demented Parkinson (PD) patients and healthy controls were examined with neuropsychological tests emphasising visuospatial abilities. Global intellectual function and general visuospatial cognition were less efficient in the two demented patient groups relative to both controls and non-demented PD patients and they did not differ significantly between non-demented Parkinsonians and controls nor between demented PD and HD patients. However, HD patients but not demented PD patients were impaired on a test of person-centred spatial judgement compared to non-demented subjects while demented PD patients scored significantly lower than HD patients on a test of field independence. Factor analysis yielded a factor reflecting general visuospatial processing capacity which discriminated between demented and non-demented PD patients but not between demented PD and HD patients. A unique factor associated with the manipulation of person-centred space discriminated between demented PD and HD patients. These results suggest general visuospatial processing is impaired as a non-specific function of dementia presence in HD and PD. Abnormalities in circumscribed aspects of visuospatial function, on the other hand, may differentiate between HD and PD, suggesting differential involvement of the basal ganglia in the respective illnesses.

Differential Classification of Dementia

In the absence of biological markers, dementia classification remains complex both in terms of characterization as well as early detection of the presence or absence of dementing symptoms, particularly in diseases with possible secondary dementia. An empirical, statistical approach using neuropsychological measures was therefore developed to distinguish demented from non-demented patients and to identify differential patterns of cognitive dysfunction in neurodegenerative disease. Age-scaled neurobehavioral test results (Wechsler Adult Intelligence Scale—Revised and Wechsler Memory Scale) from Alzheimer's (AD) and Huntington's (HD) patients, matched for intellectual disability, as well as normal controls were used to derive a classification formula. Stepwise discriminant analysis accurately (99% correct) distinguished controls from demented patients, and separated the two patient groups (79% correct). Variables discriminating between HD and AD patient groups consisted of complex psychomotor tasks, visuospatial function, attention and memory. The reliability of the classification formula was demonstrated with a new, independent sample of AD and HD patients which yielded virtually identical results (classification accuracy for dementia: 96%; AD versus HD: 78%). To validate the formula, the discriminant function was applied to Parkinson's (PD) patients, 38% of whom were classified as demented. The validity of the classification was demonstrated by significant PD subgroup differences on measures of dementia not included in the discriminant function. Moreover, a majority of demented PD patients (65%) were classified as having an HD-like pattern of cognitive deficits, in line with previous reports of the subcortical nature of PD dementia. This approach may thus be useful in classifying presence or absence of dementia and in discriminating between dementia subtypes in cases of secondary or coincidental dementia.

Differential classification of dementia.

In the absence of biological markers, dementia classification remains complex both in terms of characterization as well as early detection of the presence or absence of dementing symptoms, particularly in diseases with possible secondary dementia. An empirical, statistical approach using neuropsychological measures was therefore developed to distinguish demented from non-demented patients and to identify differential patterns of cognitive dysfunction in neurodegenerative disease. Age-scaled neurobehavioral test results (Wechsler Adult Intelligence Scale-Revised and Wechsler Memory Scale) from Alzheimer's (AD) and Huntington's (HD) patients, matched for intellectual disability, as well as normal controls were used to derive a classification formula. Stepwise discriminant analysis accurately (99% correct) distinguished controls from demented patients, and separated the two patient groups (79% correct). Variables discriminating between HD and AD patient groups consisted of complex psychomotor tasks, visuospatial function, attention and memory. The reliability of the classification formula was demonstrated with a new, independent sample of AD and HD patients which yielded virtually identical results (classification accuracy for dementia: 96%; AD versus HD: 78%). To validate the formula, the discriminant function was applied to Parkinson's (PD) patients, 38% of whom were classified as demented. The validity of the classification was demonstrated by significant PD subgroup differences on measures of dementia not included in the discriminant function. Moreover, a majority of demented PD patients (65%) were classified as having an HD-like pattern of cognitive deficits, in line with previous reports of the subcortical nature of PD dementia. This approach may thus be useful in classifying presence or absence of dementia and in discriminating between dementia subtypes in cases of secondary or coincidental dementia.

EEG frequency analysis in demented and nondemented parkinsonian patients.

In an attempt to evaluate EEG changes associated with dementia in Parkinson's disease (PD), we performed frequency analysis in three groups of 10 subjects each; two with PD, and one normal control group. The PD patient groups were matched for age, sex, severity and duration of disease, but were discordant for the existence of dementia. Normals were age- and sex-matched healthy volunteers. The relative alpha amplitude was significantly decreased in the demented PD patients, unrelated to motor disability. There was a nonsignificant but consistent trend of increased amplitude in the delta and theta range in the demented PD patients as compared to nondemented PD subjects and normal controls, as well as increased amplitude in the theta and delta range with more severe motor disability in the nondemented PD patients.

Severity and specificity of cognitive impairment in Alzheimer's, Huntington's, and Parkinson's diseases and progressive supranuclear palsy

To investigate differences in severity and specificity of cognitive impairment among various neurodegenerative diseases, we tested groups of patients presenting with senile dementia of the Alzheimer type (SDAT; 44), progressive supranuclear palsy (PSP; 45), Huntington's disease (HD; 35) and Parkinson's disease (PD; 164), with an extensive neuropsychological battery. We found dementia, as defined by a global intellectual performance 2 standard deviations lower than mean control values, in 93% of SDAT, 66% of HD, 58% of PSP, and 18% of PD patients. Specific features of cognitive impairment distinguished the four groups of patients once they were matched for level of intellectual deterioration: remote memory and linguistic disorders in SDAT, frontal lobe-like abnormalities in PSP, concentration and acquisition disorders in HD. There was no specific alteration in demented PD patients. This study demonstrates the frequency of dementia in predominantly subcortical degenerative diseases and indicates that "subcortical dementia," rather than being a homogeneous entity, should be divided into specific subtypes of cognitive impairment related to different underlying specific lesions of each disease.

Nerve growth factor receptor immunoreactivity within the nucleus basalis (Ch4) in Parkinson's disease: reduced cell numbers and co-localization with cholinergic neurons

In a effort to better define the role cholinergic basal forebrain neurons play in human cognitive processes, a quantitative assessment of cholinergic nucleus basalis (Ch4) neurons was carried out in 5 patients with Parkinson's disease (PD; 4 non-demented and 1 demented) and 4 age-matched controls using nerve growth factor (NGF) receptor immunohistochemistry as a direct marker for cholinergic basal forebrain neurons. Virtually all (>90%) NGF receptor-containing neurons co-localize with the specific cholinergic marker choline acetyltransferase (ChAT) within the nucleus basalis in PD. NGF receptor-containing neurons were reduced on average by 68% (range 38.6–87.4%) in the non-demented PD cases and by 88.6% in the demented PD patient. Loss of these neurons was heterogeneous across the nucleus basalis subfields with only the anterolateral and posterior Ch4 subregions demonstrating significant reductions of NGF receptor-containing neurons. The reduction in NGF receptor-containing neurons was accompanied by a decrease of acetylcholinesterase (AChE) containing fibers within temporal cortex and in some cases ChAT immunoreactivity in the basolateral amygdaloid nucleus. The numerous non-cholinergic AChE-rich pyramidal cells which were observed throughout the cortex of aged controls were also virtually absent in PD. Although PD patients exhibited severe reductions in Ch4 neurons, few neuritic plaques or neurofibrillary tangles were observed within the PD cortex or Ch4 and similar numbers of these AD-type pathologies were seen within age-matched controls. This suggests that Ch4 degeneration alone is not sufficient to induce such cytoskeletal abnormalities and that the neuron loss seen within Ch4 in AD and PD may be mediated through different processes. These results, coupled with the extensive basic and clinical literature linking acetylcholine and memory function, further indicate that Ch4 degeneration without additional cortical and/or subcortical pathology is not sufficient to impair cognition in PD. Perhaps additional pathology must be superimposed upon nucleus basalis degeneration to induce dementia in humans.