The clinical features of Parkinson's disease (PD) include bradykinesia, rigidity, tremor, postural instability, autonomic dysfunction, and bradyphrenia. The most frequent pathologic substrate for PD is Lewy body disease (2). Some cases of otherwise clinically typical PD have other disorders, such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA) or vascular disease, but these are uncommon, especially when the clinical diagnosis is made after several years of clinical follow-up (3,4). The diagnostic accuracy rate has approached 90% in some series (5).
The brain is usually grossly normal when viewed from the outer surface. There may be mild frontal atrophy is some cases, but this is variable. The most obvious morphologic change in PD is only visible after the brainstem is sectioned. The loss of neu-romelanin pigmentation in the substantia nigra and locus ceruleus is usually grossly apparent and may be associated with a rust color in the pars reticulata, which correlates with increased iron deposition in the tissue. Histologically, there is neuronal loss in the substantia nigra pars compacta along with compensatory astrocytic and microglial proliferation. Although biochemically there is loss of dopaminergic termini in the striatum, the striatum is histologically unremarkable. In the substantia nigra and locus ceruleus, neuromelanin pigment may be found in the cytoplasm of macrophages. Less common are neurons undergoing neuronophagia (i.e., phagocytosis by macrophages). Hyaline cytoplasmic inclusions or Lewy bodies and less well-defined "pale bodies" are found in some of the residual neurons in the substantia nigra (Fig. 2). Similar pathology is found in the locus ceruleus, the dorsal motor nucleus of the vagus, as well as the basal forebrain (especially the basal nucleus of Meynert). The convexity neocortex usually does not have Lewy bodies, but the limbic cortex and the amygdala may be affected. Depending upon the age of the individual, varying degrees of Alzheimer-type pathology may be detected, but if the person is not demented, this usually falls within the limits for that age. Some cases may have abundant senile plaques, but few or no neurofibrillary tangles (NFTs).
Lewy bodies are proteinaceous neuronal cytoplasmic inclusions (6,7). In some regions of the brain, such as the dorsal motor nucleus of the vagus, Lewy bodies tend to form within neuronal processes and are sometimes referred to as intra-neuritic
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