Pick's disease results in atrophy of the anterior portion of the frontal lobe and a characteristic atrophy of the anterior portion of the superior temporal gyrus (anterior to the central sulcus) with preservation of the posterior portions of that gyrus. The parietal and occipital lobes are generally spared. The atrophy leaves the gyri with a knife-edge appearance. The lateral ventricles, particularly the frontal horns, are dilated due to the atrophic changes. There is also a characteristic severe loss of the granular neurons that comprise the dentate gyrus of the hippocampal complex. Subcortical structures in which neuronal loss occurs include the basal ganglia, amygdala, nucleus basalis of Meyn-ert, substantia nigra, and locus ceruleus (Hof, Bouras, Perl, & Morrison, 1994; Hansen, 1994). Brain stem and cerebel-lar areas with connections to the cortex are also typically involved (Braak, Arai, & Braak, 1999; Dickson, 1998). In contrast to severely abnormal computed tomography or magnetic resonance images, electroencephalographic recordings are usually normal.
Neuropathology features of Pick's disease include severe cerebral cortical neuronal loss, Pick bodies, and ballooned neurons (Pick cells; Giannakopoulos et al., 1996). Pick bodies are intracytoplasmic argyrophilic neuronal inclusions composed of straight filaments, microtubules, and occasional paired helical filaments (similar to those in Alzheimer's disease neurofibrillary tangles; Hof et al., 1994). Although there is some neuronal loss in the nucleus basalis of Meynert, cortical levels of choline acetyltrans-ferase are not reduced in Pick's disease as they are in Alzheimer's disease.
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