Lewy Body Dementia (LBD) (together with vascular dementia) is the second most frequent cause of dementia after Alzheimer disease (AD). DLB should also be considered as a pathological continuum with Parkinson’s disease as both diseases are characterized by the presence of Lewy Bodies in the brain.
Actually, the most important pathological feature of the disease is the presence of large amounts (in Parkinson’s diseases they are less diffuse) of Lewy bodies in the substantia nigra, locus coeruleus, dorsal raphe, substantia innominate, dorsal motor nucleus of the vagus nerve and, especially neocortex.LBD diagnosis is just clinical. The key clinical features (except of course for dementia) are fluctuating cognition, attention and alertness, recurrent visual hallucinations and the presence of parkinsonian (generally symmetrical and moderate) signs. Suggestive and supportive features of LBD are REM sleep behavior disorder, severe neuroleptic sensitivity, repeated falls and syncope, systematized delusions (as par example misidentification syndromes). Differently than dementia, which is associated with Parkinson’s disease (where dementia appears after several years the onset of parkinsonisms), LBD is diagnosed when dementia precedes or is concomitant with parkinsonian signs.
Conventional brain MRI does not show specific abnormalities in LBD. The absence of significant medial lobe temporal atrophy would be another argument for LBD against AD diagnosis.
SPECT and PET images can give further elements for the diagnosis of LBD. Occipital metabolism on PET might help to distinguish DLB from AD with a 92% sensitivity and specificity. Relative sparing of mid and posterior segments of the callosal gyrus with PET images has been found to be 100% specific for LBD.
Dopamine transporter imaging (DaT-scan) could also give useful hints to distinguish patients with LBD from normal controls and patients with AD, but this remains somehow a matter of debate.
Finally, the diagnosis of LBD is essentially clinical and, as it is usual with most of the neurological diseases, the importance to collect the accurate elements of the history of the patient is of great importance for the differential diagnosis, especially in the case of LBD.
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