Spongiform change in dementia with Lewy bodies and Alzheimer disease.

Background: Dementia with Lewy bodies (DLB) is characterized neuropathologically by brainstem and cortical Lewy bodies and Lewy neurites, neuronal loss in brainstem nuclei, and Alzheimer disease (AD) pathology. Previous studies have suggested that spongiform change in the entorhinal cortex may also be a pathologic feature; however, this change has not been well characterized.

Design/method: An autopsy series of 40 subjects with DLB and 40 subjects with AD were matched on age, sex, and last Mini Mental State Examination before death. Using semistereological methods on representative sections through the transentorhinal and perirhinal cortices, quantitative counts and semiquantitative grading of vacuolization were performed by 1 rater (A.S.) blinded to subjects' diagnoses. In addition, electron microscopy of representative sections was performed.

Results: Vacuolization was 4- to 5-fold more prominent in the perirhinal, as compared with transentorhinal, cortex. Moderate to severe vacuolization was found in 57.5% of DLB, but only 7.5% of AD subjects. There were statistically significant differences between mean numbers of vacuoles in the perirhinal (DLB mean=27.91; AD mean=2.35; P<0.001) and transentorhinal (DLB mean=5.92; AD mean=0.5; P<0.001) cortices in DLB as well as AD cases. Electron microscopy revealed both axonal and dendritic pathology, with dilatation, vacuole formation, and abnormal membranous profiles.

Conclusions: Although the exact mechanism remains to be elucidated, vacuolization seems to be more specific for DLB than AD, with disproportionate involvement of the perirhinal cortex.