[Pick and focal brain atrophy]

Overlap between neurodegenerative disorders

Neurodegenerative disorders are characterized by the formation of distinct pathological changes in the brain, including extracellular protein deposits, cellular inclusions, and changes in cell morphology. Since the earliest published descriptions of these disorders, diagnosis has been based on clinicopathological features, namely, the coexistence of a specific clinical profile together with the presence or absence of particular types of lesion. In addition, the molecular profile of lesions has become an increasingly important feature both in the diagnosis of existing disorders and in the description of new disease entities. Recent studies, however, have reported considerable overlap between the clinicopathological features of many disorders leading to difficulties in the diagnosis of individual cases and to calls for a new classification of neurodegenerative disease. This article discusses: (i) the nature and degree of the overlap between different neurodegenerative disorders and includes a discussion of Alzheimer's disease, dementia with Lewy bodies, the fronto-temporal dementias, and prion disease; (ii) the factors that contribute to disease overlap, including historical factors, the presence of disease heterogeneity, age-related changes, the problem of apolipoprotein genotype, and the co-occurrence of common diseases; and (iii) whether the current nosological status of disorders should be reconsidered.

Frontal lobe degeneration of non-Alzheimer type and Pick's atrophy: lumping or splitting?

We report six cases of presenile (five) and senile (one) progressive dementia with a mild-to-marked frontal or frontotemporal atrophy and ventricular dilation (Frontal Lobe Degeneration [FLD]). The most prominent microscopic features were layer-dependent neuronal depletion of the cortex, spongiosis, and cortical and subcortical gliosis. Five cases showed additional degeneration of the S. nigra, and two also had motor neuron disease. Despite the absence of Pick cells and bodies, such cases have many features in common with Pick atrophy. Because Pick cells and bodies are inconstantly occurring features in otherwise typical cases of Pick atrophy, they cannot be regarded as inevitable markers of the latter. In our opinion, cases with mild frontal or frontotemporal atrophy as described herein and by others match the grades 1 and 2 in terms of Schneider's classification of Pick atrophy [37]. As long as the etiology of both Pick atrophy and the so-called FLD is unknown, and we finally have to follow morphological criteria for classification, there is apparently no convincing reason to introduce a separate category, such as FLD or FTA, for the cases with moderate or mild frontal atrophy and dementia of frontal lobe type, which can be sufficiently classified with the Pick spectrum of lobar atrophy.