LEWY BODY INCLUSIONS in neurons of the substantia nigra are universally recognized as the histopathological signature of idiopathic Parkinson disease (PD). Even though occasional cortical Lewy bodies can be detected in most cases of idiopathic PD, it was not until 1984 that Kosaka et al1 linked the presence of cortical Lewy bodies to dementia. Recognition of dementia with Lewy bodies (DLB) as a distinct neurodegenerative disease is therefore relatively recent, and its definition is still evolving as physicians and neuroscientists delineate its clinical and pathological dimensions. The current consensus guidelines for the pathological diagnosis of DLB2 closely follow Kosaka's original formula for describing the distribution of Lewy bodies: brainstem (idiopathic PD), limbic/transition, and neocortical (DLB). From the earliest pathological studies, however, the majority of DLB cases displayed some of the pathological changes associated with Alzheimer disease (AD), especially senile plaques (Figure 1). In this issue of the ARCHIVES, Lopez et al3 emphasize the reverse finding, namely that the majority of their cases of definite AD contained enough Lewy bodies to warrant a second diagnosis of DLB; of 19 AD cases confirmed neuropathologically, 10 had Lewy bodies. This finding extends prior reports that patients with AD commonly have the pathological changes of PD, including Lewy bodies, in the substantia nigra.4 According to Lopez et al, the coexistence of numerous Lewy bodies beyond the brainstem in AD is greater than previously reported, which suggests a need to reassess the pathological as well as clinical criteria for the diagnosis of DLB. Immunostains with antibodies directed against α-synuclein, rather than ubiquitin as stated in the guidelines, have become the method of choice to identify Lewy bodies in histological sections. Even with the current criteria, however, this study indicates that physicians are at a disadvantage compared with pathologists when it comes to detecting cortical Lewy bodies; the difficulty of assigning clinical symptoms and signs to Lewy bodies continues to challenge investigators.
Pompeu F, Growdon JH. Diagnosing Dementia With Lewy Bodies. Arch Neurol. 2002;59(1):29-30. doi:10.1001/archneur.59.1.29