Change in cognitive function in idiopathic Parkinson disease

Cognitive profile of the earliest stage of dementia in Parkinson's disease

Recently, a strong interest has emerged in recognizing Parkinson's disease dementia (PDD) at a very early stage. However, the specific profile of the earliest stages of PDD is still unclear and a matter of considerable controversy. The objective of this study was to find out early neuropsychological markers for progression of dementia in this population. Fifty-eight patients with PDD were divided into 2 subgroups on the basis of the Mini-Mental State Examination: very mild and mild. The comparison with 26 normal controls shows that very mild PDD had deficits on attention/executive functions, naming, visuospatial/constructional abilities and retrieval of the episodic memory. Patients with mild PDD showed additional deficits on coding of episodic memory. Moreover, we found that in this early stage of PDD, the progression of dementia is mainly related to deterioration of attention/executive functions as well as retrieval and coding of episodic memory.

Progression of Parkinson's disease in the clinical phase: potential markers

Neuromodulatory or even neuroprotective therapy could soon be available for Parkinson's disease (PD), raising the question of how we should define and measure disease progression. Reported evidence suggests that several symptoms worsen with disease duration. Bradykinesia, rigidity, and activities of daily living deteriorate faster at the beginning of the disease, and this deterioration is paralleled by a decline in functional presynaptic dopaminergic activity, as shown by imaging techniques. Cognitive, speech, sleep, and gait difficulties might progress linearly in proportion to disease duration. Reduced variability in heart rate, orthostatic dysfunction, and visual hallucinations start to develop at mid-stage disease and are more common in late stages than earlier stages. In this Review, we summarise our current understanding of the progression of PD-associated symptoms and markers and conclude that an effective measurement of progression of PD must adapt to the different stages of the disease. In addition to routine clinical rating scales, new quantitative assessments of motor and non-motor symptoms, which should be more broadly available, reasonably priced, and easy-to-use, are needed.

Linguistic correlates of asymmetric motor symptom severity in Parkinson's Disease

Asymmetric motor severity is common in Parkinson's Disease (PD) and provides a method for examining the neurobiologic mechanisms underlying cognitive and linguistic deficits associated with the disorder. In the present research, PD participants (N=31) were assessed in terms of the asymmetry of their motor symptoms. Interviews with the participants were analyzed with the Linguistic Inquiry and Word Count (LIWC) program. Three measures of linguistic complexity - the proportion of verbs, proportion of function words, and sentence length - were found to be affected by symptom asymmetry. Greater left-side motor severity (and hence greater right-hemisphere dysfunction) was associated with the production of significantly fewer verbs, function words, and shorter sentences. Hence, the production of linguistic complexity in a natural language context was associated with relatively greater right hemisphere involvement. The potential neurobiological mechanisms underlying this effect are discussed.

Course of cognitive decline in Parkinson's disease: a meta-analysis

A meta-analysis was conducted on 25 longitudinal studies involving 901 initially non-demented Parkinson's disease (PD) patients to examine the magnitude of decline across multiple cognitive domains associated with disease progression. Pooled effect sizes reflecting the standardized difference between baseline and follow-up neuropsychological performance were calculated for 8 cognitive domains using a random-effects model. Relatively small effect sizes were found across all cognitive domains (d = .00 - .40). During a mean follow-up interval of 29 months, significant declines were detected in global cognitive ability (d = .40), visuoconstructive skills (d = .32), and memory (d = .29). Age showed a significant relation with decline in global cognitive ability and memory. Lower educational level was associated with greater decline in all cognitive domains. Studies with longer follow-up intervals yielded larger effect sizes for global cognitive ability. In non-demented PD patients, changes in cognitive functions over time appear to be modest. Educational level, age, and length of the follow-up interval are likely to affect the magnitude of decline in several domains. Methodological flaws, such as selection bias and uncontrolled practice effects, may have caused underestimation of the true extent of decline.

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

Dementia occurs in up to 30% of people with Parkinson's disease and is a major cause of disability. Pathologically, Parkinson's dementia, where dementia follows the onset of parkinsonism by at least one year, overlaps with dementia with Lewy bodies. We review the functional impact, definitions, neuropsychology, epidemiology and pathophysiology of Parkinson's dementia, dementia with Lewy bodies and their overlap. Associated psychiatric and imaging findings are also considered. Lastly, current and emerging approaches to assessment and treatment in patients with these Lewy body associated dementias are presented.

A longitudinal study of neuropsychological change in individuals with Parkinson's disease

OBJECTIVES

Neuropsychological changes in individuals with Parkinson's disease (PD) were studied longitudinally.

METHODS

Sixty-nine idiopathic PD patients, with Mini-Mental State Examination (MMSE) scores falling within normal range, and 37 elderly control participants were given neuropsychological tests twice approximately two years apart.

RESULTS

The PD group performed poorer than the control group on Semantic Fluency, Letter Fluency, Modified Wisconsin Card Sorting Task, and Block Design at test time 1. Two years later, the PD group showed significant decline in Semantic and Letter Fluency. A subset of 12 PD patients declined in mental status by second testing (>4 MMSE points). Cox proportional-hazards models were used to see if any baseline measures were associated with relative risk of decline in mental status. In the final model, Repetition performance and Age were significantly associated with cognitive decline.

CONCLUSIONS

Consistent with previous studies, executive function tasks were those most susceptible to disease progression.

A longitudinal study of neuropsychological change in individuals with Parkinson's disease

Neuropsychological changes in individuals with Parkinson's disease (PD) were studied longitudinally. Sixty-nine idiopathic PD patients, with Mini-Mental State Examination (MMSE) scores falling within normal range, and 37 elderly control participants were given neuropsychological tests twice approximately two years apart. The PD group performed poorer than the control group on Semantic Fluency, Letter Fluency, Modified Wisconsin Card Sorting Task, and Block Design at test time 1. Two years later, the PD group showed significant decline in Semantic and Letter Fluency. A subset of 12 PD patients declined in mental status by second testing (> or =4 MMSE points). Cox proportional-hazards models were used to see if any baseline measures were associated with relative risk of decline in mental status. In the final model, Repetition performance and Age were significantly associated with cognitive decline. Consistent with previous studies, executive function tasks were those most susceptible to disease progression.

Neuropsychological follow up in patients with Parkinson's disease, striatonigral degeneration-type multisystem atrophy, and progressive supranuclear palsy

OBJECTIVES

Impairment of executive function is frequent in Parkinson's disease (PD), striatonigral degeneration-type multisystem atrophy (SND), and progressive supranuclear palsy (PSP); sometimes frank dementia is also present. However, the progression of cognitive decline has not been adequately studied. The objectives were to delineate the progression of cognitive impairment in these parkinsonisms and to elucidate interdisease differences.

METHODS

Twenty three patients with SND and 21 with PSP, referred consecutively, and 18 patients with PD matched for severity of parkinsonism were compared on a comprehensive battery of cognitive tests and motor invalidity scales. A mean of 21 months later (range 18-24 months) the patients were called for retesting.

RESULTS

Only 12 patients with PD (66.6%), 14 with SND (60.8%), and 11 with PSP (52.4%) were retested; those who dropped out refused, had died, or were too disabled. The patients with PSP performed worse than patients with PD or SND in the short tale, verbal fluency, visual search, and Benton tests at first evaluation. Overall cognitive performance was similar in the PD and SND groups except that the SND group did significantly worse on the verbal fluency test. Between group comparison of changes in scores from first to second evaluation showed that patients with PSP deteriorated significantly in the Nelson test compared with patients with PD or SND, and that patients with PSP or SND declined significantly on the visual search test compared with patients with PD. There was no difference between the groups for motor decline. Two patients with PSP were demented (DSM IV criteria) at first evaluation and six at second evaluation; no patients with PD or SND were demented at either evaluation.

CONCLUSIONS

The greater decline of patients with PSP in attention, set shifting, and categorisation abilities is probably related to the conspicuous frontal deafferentation associated with direct premotor and prefrontal involvement, and to dysfunction of the midbrain ascending activating system, known to occur in PSP.

The validity of the Hamilton and Montgomery-Asberg depression rating scales as screening and diagnostic tools for depression in Parkinson's disease

The concurrent validity of the Hamilton Rating Scale for Depression (HAMD-17) and the Montgomery-Asberg Depression Rating Scale (MADRS) against the DSM-IV diagnosis 'depressive disorder' was assessed in patients with Parkinson's disease (PD). Sixty-three non-demented Parkinson's Disease (PD) patients who attended the outpatient department of an academic hospital were diagnosed according to a standardised research protocol. This protocol consisted of the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) to establish the presence or absence of 'depressive disorder' according to the DSM-IV criteria, as well as the HAMD-17 and the MADRS. Receiver Operating Characteristics curves (ROC curves) were obtained and the positive and negative predictive values (PPV, NPV) were calculated for different cut-off scores. Maximum discrimination between depressed and non-depressed patients was reached at a cut-off score of 13/14 for the HAMD-17, and at 14/15 for the MADRS. At lower cut-offs, like 11/12 for the HAMD-17 and 14/15 for the MADRS, the high sensitivity and NPV make these scales good screening instruments. At higher cut-offs, such as 16/17 for the HAMD-17 and 17/18 for the MADRS, the high specificity and PPV make these instruments good diagnostic instruments. The diagnostics performance of the HAMD-17 is slightly better than that of the MADRS. This study shows that it is justified to use the HAMD-17 and the MADRS to measure depressive symptoms in both non-depressed and depressed PD patients, to diagnose depressive disorder in PD, and to dichotomize patient samples into depressed and non-depressed groups.

Role of dopamine in learning and memory: implications for the treatment of cognitive dysfunction in patients with Parkinson's disease

Along with dementia, Parkinson's disease (PD) is associated with subtle but widespread cognitive impairment even in the absence of clinically apparent cognitive decline. Many of the deficits are reminiscent of those observed in patients with lesions of the prefrontal cortex, that is, failure in executive function that involves skills required for anticipation, planning, initiation and monitoring of goal-directed behaviours. This paper reviews the dopaminergic brain circuitry, and preclinical and clinical evidence supporting the regulation of prefrontal cortex activity by dopamine, and the role of dopamine in cognitive impairment in patients with PD. It addresses the need to integrate these facts and the findings of positive, neutral or detrimental frontal cognitive response to dopaminergic drugs in PD which should be viewed mainly in the context of methodological differences for subject selection. The cognitive effect of levodopa does not much depend on a neuropsychological specificity of the drug, the years of evolution of the disease or the severity of the motor signs. Instead, it may be a function of the level of dopamine depletion in different parts of the basal ganglia and prefrontal cortex. Consequently, dopaminergic agents may enhance cognitive functions in some patients and impair them in others. De novo patients tend to improve during the first year of treatment; stable responders to oral levodopa tend to show no changes; and wearing-off responders tend to deteriorate with acute levodopa challenge. Enhancement and impairment of cognitive function with dopaminergic treatment is incomplete and task-specific, suggesting the need to integrate the above dopamine facts with other neurotransmitter systems findings in PD. Meanwhile, such cognitive dissociation can be useful in refining the definition of the cognitive deficit in PD patients without dementia and emphasising the need to develop new and specific strategies for treatment.

Neuropsychiatric aspects of Parkinson's disease

Previous studies of the neuropsychiatric aspects of Parkinson"s disease were frequently methodologically inadequate. Small sample sizes, selection bias, lack of diagnostic criteria of Parkinson"s disease, different definitions and assessment of neuropsychiatric symptoms, and lack of control groups seriously questioned the validity of and ability to generalize the results from many studies. During the past decade, however, several of these methodological issues have been addressed. Recent studies have found that mild cognitive impairment is very common, and dementia, depression, and psychotic symptoms develop in a large proportion of patients. Neuropsychiatric symptoms are important determinants of mortality and disease progression, as well as of the patients quality of life and course of disease, caregiver distress, and nursing home admission. Few adequately designed treatment trials have been published, but available evidence suggests that depression and hallucinations may be effectively treated using new antidepressants and atypical antipsychotic agents without worsening of parkinsonism.

Managing late complications of Parkinson's disease

Treatment of parkinsonism becomes more difficult as the disease progresses, and results from increasing neuronal degeneration, side effects from antiparkinsonian medications, or most often, a combination of each. Neurodegenerative parkinson symptoms may result from substantia nigra destruction, or from other areas in the nervous system. These include the cortex (cognitive and psychiatric disorders), brainstem (bulbar abnormalities), intermediolateral cell column (autonomic disturbances), among others. Medication side effects produce motor fluctuations, dyskinesias, delirium, hallucinations, psychosis, orthostatic hypotension, sleep disorders, and a host of other well-recognized complications. This article is divided into sections concerning motor fluctuations, gait difficulty bulbar disturbances, autonomic disturbances, sleep disorders, cognitive disorders, and psychiatric disorders, and is an attempt to provide the reader with strategies for treating common complications in the advanced Parkinson's disease patient.

Sensitivity to ageing of the limbic dopaminergic system: a review

The limbic system includes the complex of brain centres, nuclei and connections that provide the anatomical substrate for emotions. Although the presence of small amounts of dopamine (DA) in several limbic structures has been recognized for a long time, for many years it was thought that limbic DA represented a precursor of noradrenaline in the biosynthetic pathway of catecholamines. More recent evidence has shown that limbic centres and nuclei are supplied with a dopaminergic innervation arising from the ventral tegmental area (field A10) and in smaller amounts from the mesencephalic A9 field. The dopaminergic limbic system is sensitive to ageing. Parameters of dopaminergic neurotransmission (DA levels, biosynthetic and catabolic markers and DA receptors) undergo age-related changes which depend on the structure and species investigated and are characterized mainly by a decline of different parameters examined. In this paper, the influence of ageing on DA biosynthesis, levels, metabolism and receptors are reviewed in laboratory rodents, monkeys and humans as well as in cases of Alzheimer's disease and Parkinson's disease. The possibility that changes of dopaminergic neurotransmission markers in the limbic system are associated with cognitive impairment and psychotic symptoms affecting the elderly is discussed. Better knowledge of dopaminergic neurotransmission mechanisms in the so-called physiological ageing and in senile dementia may provide new insights in the treatment of behavioural alterations frequently occurring in old age.

Plasma thiamine deficiency associated with Alzheimer's disease but not Parkinson's disease

In this study we compared plasma and erythrocyte thiamine levels in a group of patients with idiopathic Parkinson's Disease (iPD) to a group of patients with probable Alzheimer's Disease (pAD). pAD patients had significantly lower plasma thiamine levels (raw and z-score) than iPD patients. A significantly higher number of pAD patients had plasma thiamine deficiencies than iPD patients. The demographics of our patient groups were similar to those reported by other investigators, making age, sex and nutritional status unlikely explanations for our findings. These results suggest that plasma thiamine deficiency is associated with pAD but not with iPD.

Electrophysiological evidence for visuocognitive dysfunction in younger non Caucasian patients with Parkinson's disease

A study of "primary" (VEPs) and "cognitive" (ERPs) visual evoked potentials was carried out in a group of non-demented Afro-American Parkinson's disease (PD) patients. Current studies suggest that differences exist in the clinical manifestations of PD in Caucasian and non-Caucasian populations. Two horizontal sinusoidal gratings differing in spatial frequency, i.e., 1 and 4 cycles per degree (cpd), were presented in an "odd-ball" paradigm to 17 patients with PD and 17 age-matched control subjects. While the 1 cpd stimulus, is not expected to reveal retinal dopaminergic deficency, but only visuocognitive deficits, the 4cpd may give direct information of both "retinal" and "cognitive" visual deficits. We measured the latencies and amplitudes of N70, P100 and P300 components, and derived the "normalized" measures of P300-N70 latency difference (Central Processing Time-CPT70), the P300-P100 latency difference (CPT100) and the P300 amplitude responses normalized to either N70 and P100 amplitude (Amplitude Ratios AR70 and AR100). Our results do show that cognitive electrophysiological deficits in younger PD patients exist in non-Caucasians, perhaps to an even greater degree than in Caucasians, and confirm that absolute and normalized ERP amplitude and latency abnormalities are a distinguishing feature of younger PD patients from controls. In particular P300 measures are abnormal for 1 cpd pattern. A negative correlation exists between P300 amplitude and the motor score. By comparing the results for 1 and 4cpd stimuli it can be concluded that "primary" and "cognitive" visual abnormalities are independently affected in PD, implying that visuo-cognitive abnormalities are not passively determined by retinal dopaminergic deficiency.