Dementia with Lewy bodies (DLB) can sometimes be difficult to distinguish from Parkinson’s disease with dementia (PDD).
Typically, DLB is faster in progression, less responsive to levodopa, and associated with visual hallucinations and fluctuations in the level of alertness. Another distinguishing point is that in DLB, the memory loss precedes the parkinsonism or begins around the same time, whereas in PDD, the parkinsonism typically precedes the memory loss by several years. One symptom seen most commonly with DLB (but also in PD) is REM sleep behavior disorder (RBD), in which there is an absence of the usual paralysis during dream sleep (rapid eye movement REM), resulting in acting out dreams.
Typically the diagnosis is based on the clinical examination, neuropsychological evaluation, and response to medication. MRI is done to exclude other causes of dementia and parkinsonism such as stroke, but there are no diagnostic findings on MRI that reliably distinguish DLB from related conditions. DaTscan and FDG-PET can distinguish between Alzheimer’s disease (the most common cause of dementia) and DLB / PDD, but there are no functional image tests that can reliably distinguish between DLB and PDD.
Treatment for Dementia with Lewy Bodies is mainly supportive, meaning medications for cognition, parkinsonism and hallucinations, but these medications tend to provide only modest, and often short-lived, benefit for DLB. Physical therapy can be helpful as well. Avoidance of neuroleptics (antipsychotics) such as haloperidol (Haldol), risperidone (Risperdal), aripiprazole (Abilify), olanzapine (Zyprexa), prochlorperazine (Compazine), metoclopramide (Reglan) is key because of the higher risk of adverse effects in patients with DLB.