Severity of cognitive impairment and the clinical diagnosis of AD with Lewy bodies.

OBJECTIVE: 1) To examine the clinical differences between AD and AD with Lewy bodies (AD+LB); and 2) to determine the accuracy of Consensus guidelines for the clinical diagnosis of dementia with Lewy bodies (DLB) at different levels of dementia severity.
METHODS: The authors examined the clinical characteristics of 185 patients with pathologically diagnosed AD alone and 60 with AD+LB. The relationship between clinical symptoms and AD+LB was determined by multivariate analyses, controlled by age, duration of symptoms, presence of cerebrovascular disease, and dementia severity.
RESULTS: Mild dementia syndrome: No specific clinical symptom was associated with the presence of AD+LB. The sensitivity of the diagnosis of DLB was 62% and specificity was 54%. Moderate dementia syndrome: Extrapyramidal signs (EPS), especially cogwheel rigidity, and major depression were associated with AD+LB. The sensitivity for DLB was 82% and specificity was 31%. Severe dementia syndrome: Cogwheel rigidity and diurnal hypersomnia were associated with AD+LB. The sensitivity for DLB was 93% and specificity was 16%.
CONCLUSIONS: The presence of EPS is not useful in differentiating AD+LB from AD in patients with mild dementia. However, as the disease progressed, they emerge as defining features, especially cogwheel rigidity. The accuracy of AD+LB diagnosis varies according the severity of the dementia syndrome. The low sensitivity and specificity in AD+LB patients with mild dementia suggest that in early stages AD+LB patients do not present the clinical characteristics of DLB. By contrast, the high sensitivity and low specificity for the diagnosis of DLB in moderate/severe dementia stages suggests that AD patients can also have characteristic symptoms of DLB. These results indicate that the antemortem diagnosis of AD+LB is difficult in all dementia stages, and better clinical and biologic differentiations of these entities are needed.