Dementia with Lewy bodies and Parkinson's disease with dementia: Are they different?
Introduction
Parkinson's disease (PD) is the most common, age-associated neurodegenerative movement disorder and is characterized by bradykinesia, rigidity, tremor, postural instability, autonomic dysfunction and bradyphrenia [1]. PD is sub-classified based upon the predominant clinical feature into akinetic-rigid and tremor-predominant types. Tremor-predominant PD may have a relatively more benign clinical course. Dementia develops in some cases of PD, particularly late in the disease course, and it appears to be more common in akinetic-rigid PD [1]. The neuropathologic substrate of PD with dementia (PDD) has been the subject of many studies [2], [3], and several recent studies have suggested that cortical Lewy body (LB) pathology may be the most common pathologic substrate of PDD [4], [5]. Alzheimer type pathology is present in most cases [6], but it is not sufficient to diagnose Alzheimer's disease (AD) with current neuropathologic criteria for AD [7].
Neurocognitive presentations of Lewy body disease (LBD) are increasingly recognized and recent studies suggest that a constellation of signs and symptoms correlate with a clinicopathologic disorder referred to as dementia with Lewy bodies (DLB) [8]. The relationship of DLB to PDD is unresolved and the topic of current research efforts. The predominant presenting clinical feature—dementia in DLB and Parkinsonism in PDD—is the major distinction between DLB and PDD. Several studies have now shown that with most diagnostic measures, there are few significant differences between DLB and PDD [9], [10]. Neuropsychiatric symptoms, especially well-formed, non-threatening visual hallucinations are one of the major clinical features of DLB [8], but hallucinations are also frequent in PD, especially after treatment with l-DOPA [11]. Delusions and violent or aggressive behavior and increased sensitivity to neuroleptic medications are additional common clinical characteristics of DLB [8]. Fluctuation, which is another major clinical feature of DLB, has proven difficult to operationalize, but has diagnostic utility in differentiating DLB from AD [12], but it is less clear if it has any differential diagnostic validity for PDD.
Most evidence would suggest that there are few differences in pathologic findings between DLB and PDD [13], but there have been few comparative studies. The purpose of this report is to compare neuropathologic features patients with antemortem clinical features consistent with DLB and PDD.
Section snippets
Materials and methods
Cases were selected from the files of the Mayo Clinic Jacksonville brain bank and were a consecutive series of cases in which adequate clinical information was available for retrospective assignment of clinical diagnoses. The material included 28 cases of DLB, 6 of PDD and 13 of PD without dementia. Clinical and pathologic features are summarized in Table 1. The cases did not differ significantly with respect to age at death, male-to-female ratio or disease duration. There were no differences
Alzheimer type pathology in DLB vs. PDD
Senile plaques (SP) and neurofibrillary tangles (NFT) were counted in sections with thioflavin-S fluorescent microscopy. The average SP count (at ×100 magnification) was determined from counts in five cortical areas (frontal, temporal, parietal, occipital and motor cortices) and four hippocampal sectors (CA4, CA2/3, CA1 and subiculum). Both DLB and PDD had more SP in the cortex and hippocampus than PD, but there were no differences between DLB and PDD. The average NFT count (at ×400
Discussion
This retrospective comparative study of DLB and PDD failed to find significant pathologic differences between DLB and PDD with respect to Alzheimer type pathology and LB pathology. The only feature that showed a trend for difference was the degree of neuronal loss in the substantia nigra. Not unexpectedly the average substantia nigra neuronal loss score was greater in PD (and PDD) than in DLB. Since both PD and PDD by definition present with Parkinsonism, while Parkinsonism is a late feature in
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