Demensia Badan Lewy

01Pathophysiology

Dementia with Lewy bodies is fundamentally a synucleinopathy, placing it in the same pathological family as Parkinson disease and multiple system atrophy. The hallmark lesion is the Lewy body, an intraneuronal cytoplasmic inclusion composed of abnormally aggregated α-synuclein protein. The PNPK Demensia 2026 recognizes α-synuclein seed amplification assays (αSyn-SAA) from cerebrospinal fluid as a co-pathology biomarker that can directly indicate Lewy-related pathology. When α-synuclein misfolds, it forms insoluble aggregates that disrupt synaptic transmission, cause mitochondrial dysfunction, and ultimately trigger neuronal death.

Unlike Parkinson disease, where Lewy body deposition begins predominantly in the brainstem (substantia nigra) and only later spreads cortically, DLB is characterized by early and widespread cortical Lewy body deposition, particularly in the temporal, parietal, and occipital cortices, alongside subcortical involvement. This cortical distribution is why patients present with cognitive symptoms first rather than motor symptoms. Importantly, PNPK Demensia 2026 states that both DLB and Parkinson disease dementia (PDD) are related to deficits in both acetylcholine and dopamine, which explains the combined cognitive-motor presentation and the therapeutic rationale for cholinesterase inhibitors.

The cholinergic deficit in DLB is even more severe than in Alzheimer disease because both the basal forebrain (nucleus basalis of Meynert) and brainstem cholinergic nuclei (pedunculopontine nucleus) are affected. This profound cholinergic loss underlies the cognitive fluctuations, visual hallucinations, and attentional deficits. It also explains why DLB patients often respond more robustly to cholinesterase inhibitors than typical Alzheimer disease patients do.

The nigrostriatal dopaminergic pathway degeneration produces the parkinsonian motor features (bradykinesia, rigidity, resting tremor). The relative timing of when this pathway degenerates, compared with cortical involvement, is what distinguishes DLB from PDD clinically. In DLB, cognitive decline occurs concurrently with or before motor symptoms; in PDD, established Parkinson disease precedes dementia by at least one year.

Occipital hypometabolism is a distinctive imaging finding in DLB. The deposition of Lewy bodies in the visual association cortex disrupts visual processing pathways, directly producing the characteristic well-formed, detailed visual hallucinations and the prominent visuospatial deficits that serve as clinical hallmarks. This stands in contrast to Alzheimer disease, where temporal and parietal metabolism is preferentially reduced, with relative sparing of the occipital lobe.

Autonomic dysfunction in DLB results from Lewy body involvement of the peripheral autonomic nervous system, including the cardiac sympathetic plexus and the enteric nervous system. This produces orthostatic hypotension, constipation, urinary incontinence, and reduced cardiac MIBG uptake, which has been incorporated as an indicative biomarker in the 2017 DLB Consortium criteria.

Finally, REM sleep behavior disorder (RBD) results from Lewy body deposition in brainstem nuclei responsible for REM atonia (sublaterodorsal nucleus/subcoeruleus complex). Loss of the normal skeletal muscle paralysis during REM sleep causes patients to physically act out their dreams, often with violent limb movements. RBD can precede cognitive symptoms by years to decades and is considered a prodromal marker of synucleinopathy.

02Classification and Clinical Manifestation

The DLB Consortium Fourth Consensus Report (McKeith et al., 2017), which is cited by the PNPK Demensia 2026 as the reference criteria for DLB diagnosis, classifies clinical features into a hierarchical system. The following table reflects this framework.

Diagnostic Classification

The 1-Year Rule: DLB versus Parkinson Disease Dementia

The PNPK Demensia 2026 explicitly describes the temporal distinction between DLB and PDD. In PDD, motor (parkinsonian) symptoms must precede dementia by at least 1 year. In DLB, motor symptoms appear within 1 year before or after the onset of dementia, and frequently develop after cognitive symptoms have already begun. When the temporal boundary is unclear, the PNPK recommends using the generic term "Lewy body disease." This rule is a favorite test-writer target.

03Diagnostic Workup

The best initial step in any patient presenting with progressive cognitive decline is a thorough clinical assessment: detailed history (from patient and informant), cognitive screening with MoCA-INA or MMSE, and a neurological examination to detect parkinsonian signs. The PNPK Demensia 2026 emphasizes that both history-taking and neuropsychological testing are essential components in diagnosing dementia (Grade C) and that full neuropsychological testing is needed for subtype determination among DA, DFT, DLB, and DV when the diagnosis remains uncertain.

Once dementia is established, the clinical profile should immediately raise suspicion for DLB if the vignette describes fluctuating cognition, visual hallucinations, visuospatial deficits with relatively preserved memory, or RBD. The next step is structural brain imaging (MRI or CT). The PNPK Demensia 2026 recommends MRI as the preferred modality over CT when available (Grade C), with non-contrast coronal CT cuts being recommended for hippocampal evaluation if MRI is not accessible. In DLB, the key finding is relative preservation of medial temporal lobe structures, distinguishing it from Alzheimer disease.

When the diagnosis remains uncertain after clinical assessment and structural imaging, functional and ligand-based imaging should be considered (PNPK Demensia 2026, performed by physicians with neurobehavior/neurodegenerative competency). The PNPK specifically recommends DaTscan SPECT to help establish the DLB diagnosis when PET scan is not available (Grade C). Reduced dopamine transporter uptake in the basal ganglia is an indicative biomarker that, combined with a single core clinical feature, meets criteria for probable DLB.

The most confirmatory test in living patients is the combination of clinical criteria with indicative biomarkers. There is no single gold standard "most accurate test" in clinical practice; definite DLB requires postmortem neuropathological examination showing Lewy body pathology. However, the combination of DaTscan showing reduced striatal uptake, MIBG scintigraphy showing reduced cardiac uptake, and PSG confirming REM sleep without atonia provides the strongest diagnostic certainty among living patients.

04Management and Treatment

The first step in managing a newly diagnosed DLB patient is to initiate a cholinesterase inhibitor. The PNPK Demensia 2026 management algorithm for Lewy body/Parkinson dementia lists rivastigmine and donepezil as the primary pharmacological interventions. Rivastigmine holds a particular recommendation for DLB: it can improve cognition (Grade A) and is also recommended for managing psychotic symptoms such as hallucinations and delusions in DLB (Grade A). Meta-analytic evidence cited in the PNPK supports the use of ChEIs for improving cognition, global function, and activities of daily living, with data suggesting that patients who do not improve are also unlikely to worsen on these agents.

For patients with severe DLB or those intolerant of oral ChEIs, the PNPK recommends considering donepezil or rivastigmine for severe DLB, and memantine for patients in whom ChEIs are not tolerated or are contraindicated. Rivastigmine transdermal patch is a good option for patients experiencing gastrointestinal side effects (nausea, vomiting), as the PNPK notes that rivastigmine produces more nausea, vomiting, tremor, and dizziness compared to placebo.

The critical "next best step" trap on examinations involves psychotic symptoms. When a DLB patient presents with hallucinations, the instinct may be to prescribe an antipsychotic. This is wrong. The PNPK Demensia 2026 explicitly warns against antipsychotic use in DLB ("hindari pada DLB"), noting that neuroleptics cause a 2-3 fold increase in mortality due to neuroleptic sensitivity reactions. The correct next step is to optimize ChEI therapy first. The PNPK states that rivastigmine at therapeutic doses (12 mg/day over 20 weeks) can reduce psychotic symptoms in DLB patients.

Criteria for discontinuing ChEIs (PNPK Demensia 2026): discontinuation should be considered when (a) clinically meaningful worsening occurs over 6 months without other contributing factors (delirium, medical illness), (b) no observable clinical benefit during treatment, (c) the individual has end-stage dementia, (d) intolerable side effects (severe nausea, vomiting, weight loss, falls), or (e) ongoing non-adherence preventing assessment of efficacy. For ChEIs prescribed for indications other than AD, PDD, DLB, or VaD (e.g., for FTD), the PNPK recommends discontinuation (Grade B).

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The Antipsychotic Trap. This is the single most tested concept in DLB. A vignette describes an elderly patient with dementia and vivid visual hallucinations. A student who does not recognize DLB will choose haloperidol or risperidone to treat the hallucinations. This is potentially fatal. The PNPK Demensia 2026 explicitly instructs clinicians to avoid antipsychotics in DLB, citing a 2-3 fold increase in mortality from neuroleptic sensitivity reactions. The correct answer is always to optimize cholinesterase inhibitor therapy (rivastigmine) first for psychotic symptoms. If a question stem describes acute worsening of rigidity, obtundation, or autonomic instability after antipsychotic administration in a demented patient, the diagnosis is neuroleptic sensitivity in the setting of unrecognized DLB.

Memory is relatively preserved early on. The hallmark cognitive deficit in DLB is in attention, executive function, and visuospatial ability, not in episodic memory. If a vignette describes a demented elderly patient who can remember recent events but cannot copy a figure, draw a clock, or navigate familiar environments, and who has fluctuating alertness, think DLB rather than Alzheimer disease. The PNPK Demensia 2026 and the DLB Consortium both emphasize that memory impairment may not be prominent in early stages.

RBD can precede cognitive decline by years. A vignette may describe a patient whose spouse reports he has been punching, kicking, and shouting during sleep for several years, and who now presents with progressive cognitive decline and visual hallucinations. The longstanding RBD is a prodromal marker that "locks in" the diagnosis toward DLB. RBD was upgraded to a core clinical feature (not just supportive) in the 2017 DLB Consortium criteria.

The 1-Year Rule Trap. Exam questions may present a patient with both parkinsonism and dementia and ask for the diagnosis. The key discriminator is timing. If the patient has had tremor and rigidity for 5 years and only recently developed cognitive decline, the answer is Parkinson Disease Dementia (PDD), not DLB. If cognitive decline and motor symptoms emerged around the same time (within 1 year of each other), the answer is DLB. The PNPK Demensia 2026 explicitly uses the 1-year rule for this distinction.

Occipital findings on imaging are the differentiator. When exam questions provide imaging data, look for occipital hypometabolism on FDG-PET or reduced occipital perfusion on SPECT. This pattern is characteristic of DLB and distinguishes it from AD (which shows temporo-parietal hypometabolism). The cingulate island sign, meaning relative preservation of posterior cingulate metabolism on FDG-PET, further supports DLB over AD.

Preserved hippocampal volume on structural imaging. An MRI showing relative preservation of medial temporal lobe volume in a patient with progressive dementia should shift your differential toward DLB and away from Alzheimer disease, where hippocampal atrophy is expected. This is a supportive biomarker per the DLB Consortium.

The "Treat Hallucinations" vs "Treat Cognition" distinction. In DLB, cholinesterase inhibitors treat both cognitive symptoms and behavioral/psychotic symptoms (hallucinations, delusions). This is different from AD, where antipsychotics are sometimes cautiously used for severe behavioral symptoms. In DLB, ChEIs are the first-line treatment for hallucinations themselves. Per the PNPK Demensia 2026, rivastigmine is recommended for managing psychotic symptoms in DLB (Grade A).

The core competency being tested in DLB questions is the ability to recognize a distinctive clinical constellation (fluctuating cognition + visual hallucinations + parkinsonism + RBD) that separates it from the more common Alzheimer pattern, and then to avoid the dangerous reflex of prescribing antipsychotics for hallucinations. Secondary competencies include correctly applying the 1-year rule to distinguish DLB from PDD, knowing the indicative biomarkers (DaTscan, MIBG scintigraphy, PSG), and understanding why the cholinergic deficit in DLB is the therapeutic target. Questions may also test your knowledge that DLB patients have more impaired ADL function compared to AD or FTD at the same level of cognitive decline, as noted in the PNPK Demensia 2026.