American Board of Internal Medicine (ABIM) Certification Practice Exam

What is a key distinguishing factor between dementia with Lewy bodies and Parkinson disease dementia?

1. The level of beta-amyloid plaques

2. The response to antipsychotic medication

3. The timing of cognitive impairment in relation to motor symptoms

4. The age of onset

The correct answer is: The timing of cognitive impairment in relation to motor symptoms

The key distinguishing factor between dementia with Lewy bodies and Parkinson's disease dementia is the timing of cognitive impairment in relation to motor symptoms. In dementia with Lewy bodies, cognitive symptoms often appear concurrently with or within a year of the onset of motor symptoms. Patients may experience fluctuations in cognition, visual hallucinations, and parkinsonian features early in the disease progression. In contrast, in Parkinson's disease dementia, cognitive impairment generally develops later, often after several years of established motor symptoms. This distinction is critical for diagnosis and can influence treatment strategies and management of the conditions. Understanding this temporal aspect is essential for clinicians as it helps distinguish between these two types of neurodegenerative disorders, both of which involve alpha-synuclein pathology but differ in their clinical presentation and progression.