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title: "Lewy Body Dementia"
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docid: "f6a4382b-f0f7-4582-a703-7f695c65656f"
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breadcrumbs:
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- "Nuclear Medicine"
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- "Central Nervous System"
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- "Neurodegeneration"
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- "Lewy Body Dementia"
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---
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# KEY FACTS
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- ## Terminology
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- Progressive neurodegenerative disease characterized by parkinsonism, visual hallucinations, fluctuations in cognition (alertness/attention), and other cognitive impairments leading to functional decline
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- ## Imaging
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- Low dopamine transporter uptake in basal ganglia on I-123 FP-CIT SPECT similar to parkinsonian syndromes
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- Decreased tracer binding may be more symmetric and diffuse when compared to typical cases of Parkinson disease (PD)
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- Cardiac sympathetic denervation on MIBG
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- Significant occipital lobe glucose hypometabolism relative to Alzheimer disease (AD) with preservation of posterior cingulate gyrus
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- ## Top Differential Diagnoses
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- PD and PD dementia (PDD)
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- AD, including posterior cortical atrophy
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- Frontotemporal dementia (FTD)
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- ## Pathology
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- Intraneuronal aggregates of α-synuclein result in neurodegeneration
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- Significant amount of Lewy body dementia (LBD) cases involve comorbid Alzheimer pathology, which can complicate decisions about amyloid-targeting therapies (ATTs)
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- ## Clinical Issues
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- Parkinsonism
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- Fluctuating cognition, especially in attention/alertness
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- Recurrent visual hallucinations
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- Progressive impairment of cognition with motor complications leading to loss of functional independence
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- REM sleep behavioral disorders
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- No current disease-modifying treatment for LBD
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# TERMINOLOGY
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- ## Abbreviations
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- Lewy body dementia (LBD)
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- ## Synonyms
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- Dementia with Lewy bodies
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- ## Definitions
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- Progressive neurodegenerative disease of brain characterized by
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- Visual hallucinations
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- Parkinsonism (bradykinesia, rigidity, tremor)
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- Fluctuations in cognition (alertness/attention)
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- REM sleep behavioral disorder
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# IMAGING
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- ## General Features
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- ### Best diagnostic clue
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- Indicative imaging criteria
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- Abnormally low dopamine transporter (DaT) binding in basal ganglia on DaT SPECT study
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- Absent myocardial uptake on MIBG [sympathetic denervation can also be seen with primary heart disease and diabetic neuropathy as well as Parkinson disease (PD) dementia (PDD)]
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- Supportive imaging criteria
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- Medial temporal lobe hypometabolism less severe than Alzheimer disease (AD) on FDG PET
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- Significant occipital lobe glucose hypometabolism relative to AD on FDG PET
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- Preservation of posterior cingulate gyrus on FDG PET (cingulate island sign)
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- ### Location
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- Cortical, subcortical, and brainstem structures; midbrain, basal ganglia, occipital lobe
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- ## Imaging Recommendations
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- ### Best imaging tool
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- DaT SPECT with I-123 ioflupane (FP-CIT)
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- Binds to DaT predominantly in presynaptic striata
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- Normal uptake in caudate and putamen
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- Abnormal DaT imaging indicative feature for LBD diagnosis
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- Compared to PD, DaT findings in LBD can be more uniformly decreased between caudate and putamen and less likely asymmetric
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- DaT imaging differentiates between LBD (abnormal DaT) and AD (normal DaT)
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- Cannot reliably distinguish between other disorders with parkinsonism
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- I-123 MIBG cardiac exam
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- Norepinephrine analogue taken up by sympathetic cardiac nerves
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- Cardiac sympathetic denervation seen with PD, PDD, and LBD
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- Usually preserved with atypical parkinsonian syndromes, AD, and frontotemporal dementia (FTD)
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- F-18 FDG PET
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- Generalized glucose hypometabolism with significant occipital lobe hypometabolism
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- Occipital lobe involvement may help distinguish from classic AD-like pattern of hypometabolism
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- Similar hypometabolic pattern seen in PD and PDD
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- Medial temporal lobe hypometabolism less severe than in AD
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- F-18 amyloid PET
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- Can be positive in 50% or more of LBD patients, possibly reflecting AD-LBD copathology
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- Important to consider DaT scan in patients with positive amyloid and any clinical concern for LBD before starting amyloid-targeting therapy (ATTs)
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- ### Protocol advice
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- I-123 ioflupane
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- Patient preparation
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- Patient should be off all interfering dopaminergic medications
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- Pretreat with thyroid blocker (oral potassium solution, Lugol) 1 hour before tracer injection
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- Pregnancy category C: Unknown whether I-123 ioflupane can cause fetal damage or early termination of pregnancy
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- Radiopharmaceutical: I-123 ioflupane
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- Dose: 3-5 mCi (111-185 MBq)
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- Dosimetry: Striata receives highest radiation exposure, followed by bladder, bowel, and lungs (assuming thyroid is blocked)
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- Image acquisition: 3-6 hours after injection
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- I-123 MIBG
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- Patient preparation
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- Patient should be off all interfering medications
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- Pretreatment with Lugol (KI) solution
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- Dose: 3-10 mCi (111-370 MBq)
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- Dosimetry: Bladder (assuming thyroid is blocked)
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- Image acquisition: Anterior planar imaging early (15 min) after injection and delayed (4 hours) after injection; can perform SPECT as well
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- Heart:mediastinum ratio calculated on delayed anterior planar image (< 1.8 concerning for denervation)
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- F-18 FDG PET
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- Patient preparation
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- Patient should fast, stop IV fluids containing dextrose, stop parenteral feeding for 4-6 hours
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- Blood sugar should be 150-200 mg/dL
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- Patient should be placed in quiet, dimly lit room prior to and after injection for 30 min
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- Radiopharmaceutical: F-18 FDG
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- Dose: 5-20 mCi (185-740 MBq)
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- Dosimetry: Urinary bladder receives largest dose
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- Image acquisition: 30-60 min after injection
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# DIFFERENTIAL DIAGNOSIS
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- [Parkinson Disease and Parkinson Disease Dementia](/document/parkinsonian-syndromes/2b99b31a-ec1a-4dce-bb63-2a101fe9f044)
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- Neurodegenerative disease that often presents with cogwheel rigidity, shuffled gate, pill-rolling tremor at rest, bradykinesia
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- Shares similar Lewy body-related neuropathology with LBD
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- Dementia may develop but generally 10 years after onset of motor symptoms
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- PDD: PD cases where dementia is diagnosed 1 year after onset of motor symptoms
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- ## Posterior Cortical Atrophy (Visual Alzheimer Disease Variant)
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- Most commonly resulting from amyloid-β and τ protein aggregates, similar to classic AD
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- Visuospatial and visuoperception deficits most common, simultanagnosia
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- FDG PET often shows hypometabolism in classic areas (precuneus, posterior cingulate, posterior temporal lobes) with atypical occipital involvement
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- Unlike LBD, tends to involve posterior cingulate, typically more occipital asymmetric hypometabolism than LBD, negative DaT and MIBG
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- [Alzheimer Disease](/document/alzheimer-disease/2aad3ac4-44fd-43e5-8e50-a86987483af3)
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- Most common cause of dementia
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- Impairments in episodic memory and other cognitive domains
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- Preservation of motor functions
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- Early F-18 FDG hypometabolism in parietotemporal and posterior cingulate cortices
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- F-18 FDG PET hypometabolism spares occipital visual cortex
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- Related to aggregation of amyloid-β and τ proteins
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- Positive on amyloid PET
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- [Frontotemporal Dementia](/document/frontotemporal-dementia/9f9eda8c-7e3c-4292-9861-4b8abc2c6474)
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- Commonly presents with personality and behavioral changes
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- Atrophy of frontal and anterior temporal lobes
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- F-18 FDG PET hypometabolism primarily in frontal/anterior temporal lobes
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# PATHOLOGY
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- ## General Features
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- ### Etiology
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- Abnormal aggregates of α-synuclein protein within neurons
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- More diffusely seen than in PD
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- ### Associated abnormalities
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- Significant amount of LBD cases involve comorbid Alzheimer pathology, which can complicate decisions about ATTs
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- LBD is diagnosed when dementia is present before or concurrently with parkinsonian features
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- ## Gross Pathologic & Surgical Features
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- Relative preservation of total brain volume relative to other dementias
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- Increased volume of lateral ventricles relative to healthy controls
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- Decreased pigmentation within substantia nigra (midbrain) and loci cerulei (pons)
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# CLINICAL ISSUES
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- ## Presentation
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- ### Most common signs/symptoms
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- Parkinsonism
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- Fluctuating cognition, especially in attention/alertness
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- Recurrent visual hallucinations
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- REM sleep behavioral disorder
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- ### Other signs/symptoms
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- Severe neuroleptic sensitivity
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- Hallucinations (other than visual)
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- Depression
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- Severe autonomic dysfunction
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- ### Clinical profile
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- 3 main types of dementia related to continuum of Lewy body clinicopathology
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- Diffuse LBD (isolated)
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- Dementia with diffuse cortical LB pathology
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- No other significant pathology (minimal plaques/tangles)
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- PDD
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- PD patients diagnosed with dementia 1 year after onset of motor symptoms
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- Onset of dementia in PD is generally 10 years after onset of motor symptoms
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- LBD-AD copathology
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- Pathology consistent with cortical LB (α-synuclein) and AD-like pathologic changes (amyloid plaques/neurofibrillary tangles)
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- Most common presentation, occurring in ~ 70% of LBD cases
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- ## Natural History & Prognosis
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- Progressive impairment of cognition with motor complications leading to loss of functional independence
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- Core features include fluctuating cognition with impact on alertness/attention, visual hallucinations, and features of parkinsonism
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- Memory loss is less prominent early symptom in LBD but may develop with progression of disease
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- Significant distinction from AD, where memory is common early symptom
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- ## Treatment
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- No current disease-modifying treatment for LBD
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- Several therapies may help alleviate common symptoms
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- Levodopa can be used for some motor symptoms
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- Cholinesterase inhibitors may be used for some cognitive symptoms
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- Can have neuroleptic malignant syndrome if given some antipsychotic medications that interact with dopamine
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# DIAGNOSTIC CHECKLIST
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- ## Image Interpretation Pearls
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- I-123 ioflupane
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- Abnormally low DaT binding in basal ganglia on DaT SPECT study
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- I-123 MIBG
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- Sympathetic cardiac denervation
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- F-18 FDG PET/CT
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- Occipital lobe hypometabolism and normal posterior cingulate gyrus (cingulate island sign) to distinguish LBD from AD
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- F-18 amyloid PET
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- Consider recommending DaT scan in patients with positive amyloid biomarkers and any clinical concern for LBD before starting ATTs
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363e0379-1464-405c-a8e1-ad3a47aac7e8
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