I read with interest the recent ARCHIVES editorial by Pompeu and Growdon.1 Although few would disagree that dementia with Lewy bodies (DLB) is "not simply a more severe form of idiopathic PD," it is not at all clear that DLB is a "distinct entity" that "must be distinguished from idiopathic PD." Compelling clinical and pathologic evidence casts considerable doubt on this hypothesis. The authors point to the more frequent occurrence of rest tremor and levodopa responsiveness in PD as differentiating parkinsonian features, citing a study comparing PD with diffuse Lewy body disease (DLBD).2 However, in this study, both of these clinical findings also occurred in most patients with DLBD, and the difference in levodopa responsiveness was not statistically significant. Thus, physicians cannot use these findings to make a clear diagnostic distinction in individual patients. Parkinsonism was otherwise identical in the 2 groups,2 and most clinicopathologic studies have reached the conclusion that the parkinsonism of DLBD is indistinguishable from PD.3-5 Cortical involvement in the patients with DLBD produced cognitive changes and reduced the likelihood of benefit from levodopa2; these same clinical features are correlated with cortical Lewy body abnormalities in patients with PD.6 Pathologic studies find no differences other than in distribution: the pathologic substrate for parkinsonism in DLB is that of PD,7 and the pathologic basis for dementia in PD is the same as in DLB.6
Riley DE. Lewy Body Disease. Arch Neurol. 2002;59(6):1043. doi:
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