How should I approach the diagnosis of Dementia with Lewy Bodies in a patient presenting with cognitive decline and visual hallucinations?

When approaching the diagnosis of Dementia with Lewy Bodies (DLB) in a patient presenting with cognitive decline and visual hallucinations, the initial steps in primary care involve a thorough assessment to rule out reversible causes before referring to a specialist service ¹,².

Initial Assessment in Primary Care:

• First, take a comprehensive history from the person with suspected dementia and, if possible, from someone who knows them well, such as a family member ². This history should include details of cognitive, behavioural, and psychological symptoms, and their impact on daily life ².
• Visual hallucinations are a key feature that should raise suspicion for DLB [1, (Petit et al., 1998)].
• Conduct a physical examination and undertake appropriate blood and urine tests to exclude reversible causes of cognitive decline, such as delirium, depression, sensory impairment (e.g., sight or hearing loss), or cognitive impairment from medicines with increased anticholinergic burden ¹,².
• Use a validated brief structured cognitive instrument, such as the 10-point cognitive screener (10-CS) or the Mini-Cog, for cognitive testing ². However, do not rule out dementia solely based on a normal score on a cognitive instrument ².
• If dementia is still suspected after these initial investigations and reversible causes have been ruled out, refer the person to a specialist dementia diagnostic service, such as a memory clinic or community old age psychiatry service ¹,².
• For people with suspected rapidly progressive dementia, refer them to a neurological service with access to tests like cerebrospinal fluid examination ¹,².

Specialist Diagnosis of Dementia with Lewy Bodies:

• Once referred to a specialist service, an initial assessment, including an appropriate neurological examination and cognitive testing, will confirm cognitive decline and rule out reversible causes ². The specialist service will then aim to diagnose a dementia subtype using validated criteria, such as the International consensus criteria for dementia with Lewy bodies ².
• Structural imaging, such as a magnetic resonance imaging (MRI) or computed tomography (CT) scan, should be included to rule out reversible causes of cognitive decline and assist with subtype diagnosis, unless dementia is well established and the subtype is clear ¹,².
• If DLB is suspected and the diagnosis remains uncertain after initial specialist assessment, further specific tests may be considered if knowing the subtype would change management ². These include:
• I-FP-CIT SPECT (DaTscan): This is recommended if DLB is suspected and the diagnosis is uncertain ¹,².
• I-MIBG cardiac scintigraphy: This can be considered if I-FP-CIT SPECT is unavailable ¹,².
• It is important to note that DLB should not be ruled out solely based on normal results from I-FP-CIT SPECT or I-MIBG cardiac scintigraphy ².
• Specialists should be aware that antipsychotics can worsen motor features and, in some cases, cause severe antipsychotic sensitivity reactions in people with DLB ¹.