What are the diagnostic criteria for Dementia with Lewy Bodies (DLB)?

Diagnostic Criteria for Dementia with Lewy Bodies

The diagnosis of probable DLB requires dementia plus two of three core clinical features: fluctuating cognition with pronounced variations in attention and alertness, recurrent well-formed visual hallucinations, and spontaneous parkinsonism (bradykinesia, rigidity, tremor, or postural instability). 1

Core Clinical Features (Need 2 of 3)

1. Fluctuating Cognition

• Cognitive changes with pronounced variations in attention and alertness occurring over minutes, hours, or days 2, 1
• Episodes of disorganized speech, staring spells, or periods of drowsiness alternating with alertness 3
• Assessment tools include the Clinician Assessment of Fluctuation (CAF) 4-item scale, Mayo Fluctuations Scale (19-item), or Dementia Cognitive Fluctuation Scale (17-item) 4

2. Recurrent Visual Hallucinations

• Well-formed, detailed visual hallucinations that are typically recurrent 2, 1
• Often involve people, animals, or complex scenes 3
• Present in approximately 77% of clinically diagnosed DLB cases 5

3. Spontaneous Parkinsonism

• Bradykinesia (slowness of movement) is essential 1
• Plus at least one of: rigidity, rest tremor, or postural instability 1
• Present in approximately 92% of clinically diagnosed DLB cases 5
• Mild symmetric extrapyramidal signs are most common 5

Supportive Features (Increase Diagnostic Confidence)

High Diagnostic Weight

• REM sleep behavior disorder (RBD) - increases odds of autopsy-confirmed DLB by 6-fold, compared to 2-fold for each core feature 6
• Severe neuroleptic sensitivity - approximately 50% of patients show severe reactions to typical and atypical antipsychotics 1
• Reduced striatal dopamine transporter uptake on I-123 Ioflupane SPECT/CT (DaTscan) 2, 1

Additional Supportive Features

• Systematized delusions (present in 46% of cases) 5
• Repeated falls (present in 42% of cases) 5
• Auditory hallucinations 3
• Autonomic dysfunction including orthostatic hypotension, urinary incontinence, and constipation 2

Diagnostic Algorithm

1. Establish dementia diagnosis first - cognitive or behavioral symptoms that interfere with daily function, represent decline from previous level, and involve impairment in at least two cognitive domains 4

2. Identify core features - systematically assess for fluctuating cognition, visual hallucinations, and parkinsonism 1

3. Apply diagnostic threshold:

   • Probable DLB: Dementia plus 2 or more core features 1
   • Possible DLB: Dementia plus 1 core feature 1

4. Consider RBD as equivalent to core feature - when RBD is added as a fourth core feature, sensitivity increases to 90% while maintaining 73% specificity 6

5. Obtain structural imaging - MRI (preferred) or CT to exclude other causes and assess for relative preservation of medial temporal lobe structures compared to Alzheimer's disease 4, 2

6. Consider functional imaging if diagnosis unclear:

   • FDG-PET/CT shows occipital hypometabolism and "cingulate island sign" 2, 7
   • I-123 Ioflupane SPECT/CT demonstrates decreased dopamine transporter uptake 2

Temporal Relationship with Parkinson's Disease

• The "1-year rule": DLB is diagnosed when dementia occurs before or within 1 year of parkinsonism onset 1
• If parkinsonism precedes dementia by more than 1 year, the diagnosis is Parkinson's disease dementia (PDD) 1
• This distinction may be difficult to apply clinically; when uncertain, use the term most appropriate to the individual patient or generic terms like "Lewy body disease" 1

Diagnostic Performance

• The consensus criteria demonstrate high specificity (73-85%) but variable sensitivity (83-90%) depending on whether RBD is included 6
• When probable DLB requires dementia plus RBD alone, sensitivity reaches 90% with 73% specificity 6
• The combination of visual hallucinations, parkinsonism, and RBD (without fluctuations) achieves 83% sensitivity and 85% specificity 6

Critical Diagnostic Pitfalls

• Do not use typical or atypical neuroleptics for behavioral symptoms - severe sensitivity reactions occur in approximately 50% of patients 1
• Fluctuating cognition is often underrecognized - present in 89% of cases but requires specific questioning about variations in attention and alertness over different time scales 5
• Parkinsonism may be mild and symmetric - unlike classic Parkinson's disease, DLB often presents with subtle, bilateral extrapyramidal signs 5
• Amyloid PET has very limited diagnostic utility - cannot distinguish DLB from other dementias and should not be used for this purpose 2