LBD

LBD, or Lewy body dementia, is an umbrella term for a group of neurodegenerative disorders characterized by abnormal protein deposits called Lewy bodies, primarily composed of alpha-synuclein, in brain cells. It encompasses two clinically defined conditions: dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD). In many cases, clinicians use LBD to refer to both conditions when dementia and parkinsonian features are present.

Pathology and biology: Lewy bodies accumulate in cortical and subcortical regions, disrupting neural networks involved in memory, attention, movement, and autonomic function. The pattern and distribution of Lewy bodies help drive the characteristic clinical features and rate of progression. Cholinergic and dopaminergic system dysfunction are common, contributing to cognitive impairment and movement symptoms.

Clinical features: LBD presents with core features including fluctuating cognition with pronounced variations in attention and alertness, recurrent visual hallucinations, and parkinsonism (slowness of movement, stiffness, tremor). REM sleep behavior disorder and autonomic symptoms (orthostatic hypotension, urinary dysfunction) are common. Patients often have sensitivity to antipsychotic medications, which can worsen motor symptoms.

Diagnosis: Diagnosis is primarily clinical, supported by history and examination. Core features, along with supportive features such as abnormal dopamine transporter imaging or rapid eye movement sleep disorder, aid accuracy. Distinguishing DLB (dementia preceding or occurring within the first year of parkinsonism) from PDD (dementia developing after established PD) can guide management.

Management: There is no cure. Treatment focuses on symptom relief and safety. Cholinesterase inhibitors may help cognition; memantine is used variably. Levodopa can improve parkinsonism but may have limited effect on cognition. Antipsychotics should be used with caution due to sensitivity; nonpharmacologic approaches and caregiver support are important.

Prognosis and epidemiology: LBD is a leading cause of degenerative dementia, typically occurring in older adults. Progression is variable, with survival commonly several years after diagnosis. Ongoing research seeks better biomarkers and disease-modifying therapies.