Gray matter atrophy in Parkinson disease with dementia and dementia with Lewy bodies

Background: The nosologic relationship between dementia with Lewy bodies (DLB) and Parkinson disease with dementia (PDD) is continuously being debated. We conducted a study using voxel-based morphometry (VBM) to explore the pattern of cortical atrophy in DLB and PDD. Methods: Seventy-four patients and healthy elderly were imaged (healthy elderly n = 20, PDD n = 15, DLB n = 18, and Alzheimer dementia [AD] n = 21). Three dimensional T1-weighted MRI were acquired, and images analyzed using VBM. The following diagnostic criteria were used: criteria proposed by the third report of the DLB Consortium for DLB, the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Diseases Association criteria for AD, and Diagnostic and Statistical Manual of Mental Disorders, fourth edition criteria for dementia in PDD. Results: Overall dementia severity was similar in the dementia groups. We found more pronounced cortical atrophy in DLB than in PDD in the temporal, parietal, and occipital lobes. Patients with AD had reduced gray matter concentrations in the temporal lobes bilaterally, including the amygdala, compared to PDD. Compared to DLB, the AD group had temporal and frontal lobe atrophy. Conclusion: We found that despite a similar severity of dementia, patients with dementia with Lewy bodies (DLB) had more cortical atrophy than patients with Parkinson disease with dementia (PDD), indicating different brain substrates underlying dementia in the two syndromes. Together with previous studies reporting subtle clinical and neurobiologic differences between DLB and PDD, our findings support the hypothesis that PDD and DLB are not identical entities, but rather represent two subtypes of a spectrum of Lewy body disease.