Dementia with Lewy Bodies (DLB)
This patient's presentation of visual and auditory hallucinations combined with memory loss and cognitive impairment (MoCA 18) is most consistent with Dementia with Lewy Bodies (DLB), not Alzheimer's disease. 1
Diagnostic Reasoning
The constellation of visual hallucinations, auditory hallucinations, and cognitive impairment strongly points to DLB rather than Alzheimer's disease, as visual hallucinations are not a core feature of Alzheimer's and when present suggest alternative pathology. 1 The MoCA score of 18 indicates dementia-level impairment, confirming this is dementia rather than mild cognitive impairment. 1
Key Distinguishing Features of DLB
Visual hallucinations are a core clinical feature of DLB, typically presenting as recurrent, well-formed, detailed hallucinations involving people, animals, or objects. 2, 1 These occur in approximately 60-93% of DLB patients. 3, 4
Auditory hallucinations are also common in DLB (occurring in 35.5% of patients), and critically, 90.9% of DLB patients with auditory hallucinations also have visual hallucinations. 3 Patients typically describe auditory hallucinations as "hearing a soundtrack of the scene" accompanying their visual hallucinations. 3
Additional Core Features to Assess
You should specifically evaluate for three other core features of DLB that may be present: 1
- Fluctuating cognition: Pronounced variations in attention, alertness, and cognitive function occurring over minutes, hours, or days, including transient episodes of unresponsiveness 1
- Parkinsonism: Spontaneous extrapyramidal motor symptoms including bradykinesia, rigidity, tremor, and postural instability 1
- REM sleep behavior disorder (RBD): Acting out dreams during sleep due to lack of normal muscle paralysis during REM sleep, which may have preceded cognitive symptoms by years 1
Critical Diagnostic Pitfall
Do not diagnose Alzheimer's disease when core DLB features are present, even if amyloid biomarkers are positive. 1 The clinical phenotype takes precedence over biomarker results, as mixed pathology (DLB + Alzheimer's) occurs in over 50% of DLB cases. 1
Recommended Diagnostic Workup
Obtain brain MRI without contrast to exclude structural abnormalities and assess for relative preservation of medial temporal lobe structures, which supports DLB over Alzheimer's disease. 1 Consider DaTscan imaging, which shows decreased striatal dopamine transporter uptake in DLB but is normal in Alzheimer's disease. 1
Management Implications
Cholinesterase inhibitors, particularly rivastigmine, are first-line treatment for both cognitive symptoms and visual hallucinations in DLB. 5, 2, 1, 6 This differs from Alzheimer's disease where hallucinations typically occur only in later stages. 5
Traditional antipsychotics must be absolutely avoided due to severe neuroleptic sensitivity in DLB patients, which significantly increases morbidity and mortality. 1 If severe behavioral symptoms require pharmacological intervention after non-pharmacological approaches fail, atypical antipsychotics like quetiapine may be used with extreme caution. 5, 6
Prognostic Considerations
DLB is associated with a poorer prognosis, higher healthcare costs, and greater impact on quality of life compared to Alzheimer's disease. 1 The median age of onset for DLB (76.3 years) is younger than Parkinson's disease dementia (81.4 years). 6