Which of the following is a biomarker used in the diagnostic criteria for Lewy Body Dementia?

• A. Recurrent visual hallucinations
• B. Reduced dopamine transporter uptake in basal ganglia by PET or SPECT
• C. Fluctuating cognition with varying levels of alertness
• D. REM sleep behavior disorder

Answer: (B)

A key idea here is that imaging evidence of dopaminergic degeneration serves as an objective biomarker in Lewy body dementia. Reduced dopamine transporter uptake in the basal ganglia on PET or SPECT reflects loss of dopaminergic neurons in the nigrostriatal pathway, which is characteristic of Lewy body disease. This imaging finding helps confirm the diagnosis when combined with the clinical picture, because you’re seeing a biological change tied to the underlying pathology rather than just symptoms.

Clinical features like recurrent visual hallucinations, fluctuations in alertness, and REM sleep behavior disorder are important signs that raise suspicion for Lewy body dementia, but they’re diagnostic features observed clinically. They aren’t imaging biomarkers themselves. The imaging biomarker provides concrete, objective evidence of dopaminergic system involvement, strengthening the diagnostic assessment beyond symptoms alone.