Neurology · Dementia
The facts most likely to be tested
Press 1–5 to rate · ↑↓ to navigate
Lewy Body Dementia is characterized by the clinical triad of fluctuating cognition, recurrent visual hallucinations, and parkinsonism.
The presence of well-formed visual hallucinations early in the disease course is a hallmark feature that helps differentiate it from Alzheimer disease.
Patients exhibit parkinsonism (bradykinesia, resting tremor, or rigidity) that occurs within one year of the onset of cognitive decline.
REM sleep behavior disorder, characterized by acting out dreams, is a highly specific prodromal symptom of Lewy Body Dementia.
Severe neuroleptic sensitivity occurs in these patients, leading to profound worsening of parkinsonism and potential neuroleptic malignant syndrome if antipsychotics are administered.
Pathologically, the disease is defined by the presence of alpha-synuclein protein aggregates known as Lewy bodies in the cortex and brainstem.
First-line pharmacologic treatment for cognitive symptoms is cholinesterase inhibitors (e.g., donepezil or rivastigmine).
Vignette unlocked
A 74-year-old male is brought to the clinic by his wife due to progressive memory loss and behavioral changes over the past 18 months. She reports that he frequently describes seeing small children playing in the living room when no one is there. He has also begun acting out his dreams by punching and kicking during the night. On physical examination, he demonstrates masked facies, cogwheel rigidity, and a shuffling gait. His cognitive status appears to fluctuate significantly throughout the day.
What is the most likely diagnosis?
Lewy Body Dementia
The patient presents with the classic triad of fluctuating cognition, visual hallucinations, and parkinsonism, supported by the highly specific finding of REM sleep behavior disorder.
Full handout
High yield triage
Etiology / Epidemiology
Second most common neurodegenerative dementia; older age and male sex are primary risk factors.
Clinical Manifestations
Triad of visual hallucinations, parkinsonism, and fluctuating cognition.
Diagnosis
Clinical diagnosis based on McKeith criteria; polysomnography confirms REM sleep behavior disorder.
Treatment
Donepezil for cognitive symptoms; avoid typical antipsychotics due to severe sensitivity.
Prognosis
Progressive decline; mean survival 5-8 years from symptom onset.
Full handout
Epidemiology & Etiology
Prevalence increases significantly after age 65. It is characterized by the abnormal accumulation of alpha-synuclein protein aggregates in the cerebral cortex.
Pertinent Anatomy
Pathology involves widespread cortical and subcortical neuronal loss. The substantia nigra involvement explains the motor symptoms, while cortical involvement drives cognitive decline.
Pathophysiology
Intracellular inclusions known as Lewy bodies disrupt synaptic function and neurotransmitter signaling. Depletion of acetylcholine and dopamine pathways leads to the characteristic cognitive and motor deficits.
Clinical Manifestations
Patients present with visual hallucinations that are typically well-formed and recurrent. Parkinsonism (bradykinesia, rigidity) occurs, often alongside fluctuating alertness. Severe neuroleptic sensitivity can lead to irreversible parkinsonism or autonomic instability if antipsychotics are administered.
Diagnosis
Diagnosis is clinical, requiring dementia plus two of three core features: visual hallucinations, fluctuating cognition, or spontaneous parkinsonism. REM sleep behavior disorder is a highly specific supportive feature. SPECT/PET imaging showing reduced dopamine transporter uptake in the basal ganglia can support the diagnosis.
Treatment
Donepezil or rivastigmine (cholinesterase inhibitors) are the first-line treatment for cognitive and neuropsychiatric symptoms. Avoid typical antipsychotics; if psychosis is refractory, use low-dose quetiapine or clozapine with extreme caution. Treat motor symptoms with levodopa, though efficacy is often limited compared to Parkinson disease.
Prognosis
The disease is relentlessly progressive with high mortality due to falls, dysphagia, and pneumonia. Regular monitoring for orthostatic hypotension and aspiration risk is mandatory.
Differential Diagnosis
Alzheimer disease: memory loss precedes motor symptoms
Parkinson disease dementia: motor symptoms precede cognitive decline by >1 year
Vascular dementia: stepwise decline with focal neurologic deficits
Frontotemporal dementia: early personality changes and language dysfunction
Delirium: acute onset with identifiable underlying medical trigger