Differential degeneration of the locus coeruleus in dementia subtypes

Objective: Neuronal loss in the locus coeruleus (LC) is common in Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). The aims of the present study were to investigate LC degeneration in different dementia disorders including vascular dementia (VaD) and frontotemporal lobar degeneration (FTLD), to compare LC degeneration with severity of pathology in AD and DLB/PDD, to further evaluate the usefulness of a previously presented scoring system and to examine the predictive value of macroscopic assessment of the LC. Methods: A horizontal mid-level section of the pons was examined in 200 neuropathologically examined cases with clinical dementia. A previous macroscopic assessment of the LC was performed in 149 of the cases. Results: Cases with DLB/PDD and AD presented with the highest microscopic LC degeneration scores, with significant differences compared to combined AD + VaD, in turn with a higher score than VaD, FTLD and other dementia disorders. Interrater agreement (weighted K) for LC degeneration scoring was 0.83 - 0.91. DLB/PDD, AD and AD + VaD were the diagnoses for 85% of the cases with macroscopic LC depigmentation. Conclusion: LC degeneration, which may be macroscopically noted, often indicates synuclein and/or Alzheimer pathology among demented. When clinical information is scarce or inconsistent, a macroscopic assessment of the LC may facilitate focusing of the subsequent neuropathological investigation. Also, the semiquantitative scoring system is a reliable tool for histological assessment of LC degeneration.