American Board of Internal Medicine (ABIM) Certification Practice Exam

What aspect of dementia with Lewy bodies differentiates it from Parkinson disease dementia?

1. Presence of hallucinations

2. Timing of cognitive and motor symptom onset

3. Response to levodopa treatment

4. Age at diagnosis

The correct answer is: Timing of cognitive and motor symptom onset

Dementia with Lewy bodies (DLB) is characterized by a distinct timeline of symptom development compared to Parkinson's disease dementia (PDD). In DLB, cognitive symptoms typically occur before or concurrently with motor symptoms, which is a defining feature of the condition. This timing is crucial because it influences the diagnosis and management of patients presenting with symptoms. In contrast, Parkinson's disease dementia arises after a patient has established Parkinsonian motor symptoms. Cognitive decline typically manifests years after the initial diagnosis of Parkinson's disease, reinforcing the differentiating factor of timing. This distinction allows clinicians to recognize the underlying pathology and guide treatment more effectively. While aspects such as the presence of hallucinations and response to medication can play a role in the clinical context, the crucial differentiator between DLB and PDD lies in when the cognitive symptoms emerge in relation to motor symptoms.