Prodromal stage of disease (dementia) with Lewy bodies, how to diagnose in practice?

Disease with Lewy bodies or dementia with Lewy bodies (DLB), particularly at the prodromal stage, is a complex disease to diagnose because of different clinical beginnings and variable paths in terms of clinical expression. Thus DLB can be entcountered in different input modes: mild cognitive impairment, depression, acute behavioral disorders, confusion and delirium, or sleep disorders. In the aim to better diagnose the disease, should be sought obviously to search for the key symptoms: fluctuations, hallucinations, extra-pyramidal syndrome, and REM sleep behavior disorder. These symptoms are more subtle at the prodromal stage (mild neurocognitive disorder) than at the major stage. Thus fluctuations can be cognitive, simply as attentionnal fluctuations, or of alertness, such as sleepiness or more frequent nap; the visual phenomena can begin by sensation of passage, sensation of presence, or illusions; the extra-pyramidal syndrome can be really subtle such as isolated amimia or rigidity detected only with Froment's manœuvre. The frequent accompagnying symptoms are autonomic symptoms such as rhinorrhea or constipation, or sensorial symptoms such as olfactory impairment. The clinician has to be aware of the frequent presence of geriatric syndroms, also at the prodromal stage and including: falls, orthostatic hypotension, syncopa, urinary troubles, depression, delirium (after surgery, during infection...). On neuropsychological tests, sub-cortical frontal syndrome is frequent, visual memory impairment, visuospatial impairment and visuo-constructive difficulties are also characteristics. On brain MRI, isolated diminished insula is to look for. CSF analysis is usually normal but sometimes with low Abeta-42. Dat-Scan and MIBG scintigraphy were not enough explored in this context. Thus, with every patient presenting a compatible input mode, the search for symptoms of DLB has to be systematic, in the aim to have an etiological diagnosis of prodromal DLB, to avoid adverse drug events (neuroleptics) and to optimize care for patients.