Dementia with Lewy Bodies (DLB)
This elderly man's presentation of fluctuating cognition, visual hallucinations of deceased relatives, falls, and relatively preserved memory on brief testing is highly characteristic of Dementia with Lewy Bodies, not Alzheimer's disease. 1
Why This is Lewy Body Dementia
Core Clinical Features Present
Fluctuating cognition is characterized by pronounced variations in attention, alertness, and cognitive function that occur over minutes, hours, or days—this patient demonstrates this with his drifting off and episodes of altered awareness 1, 2
Recurrent visual hallucinations are typically well-formed, detailed visual hallucinations involving people (like seeing deceased relatives), animals, or objects—this is a hallmark diagnostic feature of DLB 1, 3
Falls in this context likely represent either the fluctuating consciousness component or early parkinsonism (postural instability), both core features of DLB 4, 1
Why the "Normal" Mini Test is Misleading
The Mini-Mental State Examination (MMSE) can appear relatively preserved in early DLB because memory is often less severely affected initially compared to Alzheimer's disease—DLB primarily affects attention, executive function, and visuospatial abilities rather than memory encoding 1, 5
The ability to "remember a few words" reflects relatively preserved medial temporal lobe structures in DLB, which contrasts with the prominent temporal lobe atrophy seen in Alzheimer's disease 1
Cognitive fluctuations mean testing results vary dramatically depending on when the assessment occurs—a patient may perform normally during a lucid period but show severe impairment hours later 2, 6
Diagnostic Certainty
The National Institute on Aging-Alzheimer's Association guidelines explicitly state that probable Alzheimer's dementia should NOT be diagnosed when core DLB features (visual hallucinations, parkinsonism, cognitive fluctuations) are present, even if other biomarkers suggest Alzheimer's pathology 1
The presence of two or more core features (fluctuating cognition + visual hallucinations) establishes a diagnosis of probable DLB 3, 7
Critical Management Implications
Medication Safety—Life-Threatening Concern
Traditional antipsychotics must be absolutely avoided due to severe neuroleptic sensitivity that occurs in approximately 60% of DLB patients and significantly increases morbidity and mortality 1, 3, 7
This neuroleptic sensitivity can be life-threatening and represents one of the most important reasons to correctly identify DLB 7
First-Line Treatment
Cholinesterase inhibitors (rivastigmine or donepezil) are first-line treatment for both cognitive symptoms and visual hallucinations in DLB 1, 8, 3
Rivastigmine has demonstrated particular efficacy in DLB, with the 6-12 mg per day dose showing statistically significant superiority over placebo in cognitive outcomes 8
Additional Evaluation Needed
Assess for REM sleep behavior disorder (acting out dreams)—this often precedes other DLB symptoms by years and further confirms the diagnosis 1
Evaluate for autonomic dysfunction including orthostatic hypotension, urinary incontinence, and constipation, which are common supportive features 4, 1
Screen for parkinsonism (bradykinesia, rigidity, tremor, postural instability) which may be subtle early on 1, 3
Diagnostic Work-Up
Brain MRI to assess for relative preservation of medial temporal lobe structures (supports DLB over Alzheimer's) and exclude structural lesions 1
DaTscan (dopamine transporter imaging) shows reduced striatal uptake in DLB but is normal in Alzheimer's disease—this provides Level A evidence supporting DLB diagnosis 1
Orthostatic blood pressure measurement to assess for autonomic dysfunction 4
Common Pitfall to Avoid
The single most important pitfall is misdiagnosing DLB as Alzheimer's disease with behavioral disturbances and prescribing antipsychotics for the hallucinations—this can be fatal 1, 3, 7. The presence of prominent visual hallucinations early in the disease course, combined with fluctuating cognition, essentially excludes pure Alzheimer's disease as the primary diagnosis 1.