What are the key clinical features that differentiate Dementia with Lewy Bodies from Alzheimer's disease?

Differentiating Dementia with Lewy bodies (DLB) from Alzheimer's disease (AD) relies on several key clinical features.

• Cognitive Fluctuations: A hallmark of DLB is pronounced fluctuations in cognition, attention, and alertness, which are less typical in AD McKeith et al. 2005.
• Recurrent Visual Hallucinations: Well-formed and detailed recurrent visual hallucinations are a core feature of DLB, often appearing early in the disease course McKeith et al. 2005. While hallucinations can occur in AD, they are generally less frequent and tend to appear later in the disease progression Jellinger 2018.
• Spontaneous Parkinsonism: Motor symptoms such as bradykinesia, rigidity, and tremor, characteristic of Parkinsonism, are core features of DLB and often emerge within one year of cognitive decline McKeith et al. 2005Gomperts 2016. In contrast, Parkinsonism is not a primary feature of AD and, if present, typically manifests much later in the disease course Jellinger 2018.
• Antipsychotic Sensitivity: People with DLB are highly sensitive to antipsychotic medications, which can worsen their motor features and lead to severe adverse reactions NICE CKS. This sensitivity is not a characteristic of AD NICE CKS.
• Memory Impairment: While memory impairment is prominent in AD, particularly verbal episodic memory NICE NG97, it may be less severe in early DLB, with more pronounced deficits often seen in executive function and visuospatial abilities Gomperts 2016.

Specialist investigations can also aid in differentiation; for suspected DLB, I-FP-CIT SPECT or I-MIBG cardiac scintigraphy may be used if the diagnosis is uncertain NICE CKS,NICE NG97. For suspected AD, FDG-PET, perfusion SPECT, or cerebrospinal fluid examination for tau and amyloid proteins can be considered NICE CKS,NICE NG97. Structural imaging like MRI or CT scans are used to rule out reversible causes of cognitive decline and assist with subtype diagnosis in both conditions NICE CKS,NICE NG97. However, a diagnosis of DLB should not be ruled out solely based on normal I-FP-CIT SPECT or I-MIBG cardiac scintigraphy results NICE NG97. Similarly, AD should not be ruled out based solely on CT or MRI scans NICE NG97.