Dementia in movement disorders

Selective deficits in Alzheimer and parkinsonian dementia: visuospatial function

Deficits in visuospatial cognition are frequently cited as an important component of the cognitive changes accompanying Parkinson's disease. To characterize possible differences between Parkinson's (PD) and Alzheimer's (AD) dementia, patients from both groups, matched for overall dementia severity, age and education, were contrasted neuropsychologically. Visuospatial tasks dissociated from memory, were significantly compromised in both patient groups. Differential impairment was evident on visuospatial abstraction and reasoning (Object Assembly), which was most deficient in PD. Visuospatial cognition associated with memory, classified both patient groups as impaired compared to controls, but AD patients demonstrated substantially lower performance levels than those with PD. Parkinsonian dementia thus appears to have some distinct features compared to Alzheimer's disease, which may indicate differences in underlying pathogenic mechanisms.

The relationship between Alzheimer's disease, Parkinson's disease and motor neuron disease

We argue against the dominant status assigned to conventional microscopy in the categorization of disorders such as Alzheimer's disease, Parkinson's disease and ALS. As an example we criticize the emphasis that has been placed on correlating the presence of Lewy bodies with the diagnosis of Parkinson's disease. In essence, we submit that Parkinson's disease can exist without Lewy bodies, and Lewy bodies can exist without Parkinson's disease. Nevertheless, we consider that the newer techniques available to histology have led to an important concept that constitutes a shared feature for Alzheimer's disease. Parkinson's disease and ALS; they are all characterized by the deposition of cytoskeletal debris in tissue, so they may perhaps be collectively termed the "Cytoskeletal Disorders".

Neuropathological distinction between Parkinson's dementia and Parkinson's plus Alzheimer's disease

The distinctive clinical features of dementia in Parkinson's disease (PDD) and Parkinson's plus Alzheimer's disease (PD + AD) suggest different patterns of cerebral atrophy in these conditions. To determine the pathoanatomical substrates of dementia in PDD and PD + AD, morphometric analysis of 5 standardized coronal slices was used to identify volumetric changes in cerebral tissue. In PDD (n = 4) there were 9 to 23% reductions in cross-sectional area of cerebral cortex, a 38% loss of tissue in the globus pallidus + putamen, and an 18% reduction in area of the amygdala, whereas in PD + AD (n = 6) there was severe global atrophy of the cerebral cortex (27-29% reductions), moderate atrophy of white matter (10-19% reductions), and 40% reductions in areas of globus pallidus + putamen and the amygdala relative to neuropathologically intact controls (n = 14). Immunostaining with anti-glial fibrillary acidic protein disclosed significant gliosis of all four major subdivisions of neocortex in PD + AD and gray matter of the caudate, putamen, globus pallidus, and thalamus in both PDD and PD + AD relative to controls. The findings suggest that dementia in PDD is mainly subcortical in origin and due to neuronal degeneration in basal ganglia, the amygdala, and thalamus. In PD + AD the same pattern and degree of subcortical degeneration is evident, but there are clearly superimposed lesions involving cortical neurons and long projection fibers coursing through cerebral white matter that most likely account for the distinctive manifestations of dementia in this condition compared with PDD.

The role of clinical neuropsychology in the neurological diagnosis of Alzheimer's disease

This survey on the early diagnosis of Alzheimer's disease (AD) reinstates the role of clinical neuropsychology in describing the cognitive status of AD and its evolution. The role of clinical neuropsychology is restricted to the clinical diagnosis of organic mental deterioration and its contribution to the diagnosis of AD is separate from that of neurology and neuroradiology. The frequency of a single neuropsychological disturbance in early AD patients is illustrated by our own observations.

Dementia and treatment with L-dopa in Parkinson's disease

We compared the neuropsychological performance of patients with Parkinson's disease who were young at onset of the disease (mean age, 41.4 years) and had received prolonged L-dopa treatment (mean, 52.1 months) with nontreated patients of the same age. A similar comparison was made for patients who were older at onset of the disease (mean, 62.1 years). There were no significant differences in cognitive and memory functions between the L-Dopa-treated and untreated young patients, whereas the L-Dopa-treated patients in the older age group performed more poorly than untreated patients in some memory tests (Wechsler Memory Scale I: logical and visual) and cognitive functions (Wechsler Adult Intelligence Scale: similarities, block design, and cognitive flexibility). Treatment duration, disease duration, and mean L-Dopa dose were comparable for the two age groups. After linear effects of age and disease duration had been eliminated, the duration of L-Dopa treatment did not correlate with the cognitive variables studied. These observations suggest that treatment with L-Dopa may not be the cause of cognitive impairment in Parkinson's disease.