Dementia with Lewy Bodies

Symptoms

• Cognitive fluctuations: pronounced day-to-day or hour-to-hour variation in attention, alertness, and coherence
• Recurrent visual hallucinations — typically well-formed people or animals, often non-threatening
• REM sleep behavior disorder — dream enactment, often years before cognitive decline
• Parkinsonism: bradykinesia, rigidity, gait disturbance; tremor less prominent than in PD
• Severe neuroleptic sensitivity — sometimes the presenting clue when an antipsychotic provokes rigidity, confusion, or NMS
• Autonomic dysfunction: orthostatic hypotension, constipation, urinary urgency, anosmia
• Recurrent unexplained falls and syncope

Signs / physical exam

• Parkinsonian motor exam (symmetric bradykinesia and rigidity > rest tremor)
• Postural instability and gait impairment
• Cognitive testing: deficits in attention, executive function, and visuospatial processing (clock draw, pentagons)
• Memory often relatively preserved early — distinguishes from AD

Classic findings

Elderly patient with fluctuating cognition + well-formed visual hallucinations + parkinsonism + history of acting out dreams.

Diagnostic criteria

McKeith 2017 criteria: dementia + core features (fluctuating cognition, visual hallucinations, RBD, parkinsonism). Probable DLB = ≥2 core features OR 1 core + ≥1 indicative biomarker (DaTscan, MIBG, polysomnography-confirmed RBD).

Labs

• TSH, B12, syphilis, HIV (reversible cognitive impairment screen)
• Comprehensive metabolic panel
• Polysomnography to confirm RBD (REM sleep without atonia)

Imaging

• MRI brain — relative sparing of medial temporal lobes (vs prominent hippocampal atrophy in AD)
• DaTscan SPECT — reduced striatal dopamine transporter uptake (indicative biomarker)
• FDG-PET — occipital hypometabolism with cingulate island sign
• MIBG cardiac scintigraphy — reduced uptake reflecting cardiac sympathetic denervation

First-line

• Cholinesterase inhibitors — rivastigmine (oral or transdermal), donepezil, galantamine — among the most responsive dementias to these agents; reduce hallucinations and improve cognition
• Memantine — adjunct in moderate-severe disease
• Carbidopa-levodopa for parkinsonism — start low, titrate slowly; full PD doses risk worsening hallucinations and confusion
• Clonazepam (low dose) or melatonin (3-12 mg) at bedtime for REM sleep behavior disorder; melatonin generally preferred in DLB due to less cognitive impact

Psychosis management

• First, reduce or stop offending medications (anticholinergics, dopamine agonists, amantadine)
• Pimavanserin (selective 5-HT2A inverse agonist) — preferred when pharmacotherapy needed; FDA-approved for PD psychosis with growing DLB use
• Low-dose quetiapine or clozapine if pimavanserin unavailable
• STRICTLY AVOID typical antipsychotics (haloperidol, fluphenazine) — risk of severe neuroleptic sensitivity reaction (rigidity, hyperthermia, autonomic instability, death)

Autonomic and sleep symptoms

• Orthostatic hypotension: fluid/salt, compression stockings, midodrine, droxidopa, fludrocortisone
• Constipation: hydration, fiber, laxatives
• Excessive daytime sleepiness: address sleep architecture, careful use of modafinil

Second-line / adjunct

• Physical, occupational, and speech therapy
• Caregiver education and support; advance care planning early in disease course