Comparative studies of clinical features in PD-D and DLB
The overall profile of cognitive deficits is similar in the two syndromes, with both PD-D and DLB patients exhibiting significantly more marked executive and attentional deficits, fluctuating attention, and less severe memory deficits than those with AD . Some studies have reported more pronounced executive dysfunction in DLB than in PD-D, in particular in patients with mild dementia [51, 52]. In addition, more pronounced auditory attentional disturbances were identified in PD-D compared with DLB . The finding of more pronounced differences between DLB and PD-D in early rather than later disease is consistent with the electroencephalogram (EEG) findings . A study of pre-pulse inhibition, a paradigm which enables the study of basic attention processes independent of task understanding and deliberate participation, demonstrated more pronounced impairment in DLB than PD-D . A recent study has shown that the more pronounced cognitive impairment in DLB compared with PD-D is already present in the mild cognitive impairment stage of the two diseases . Although studies based on group means provide important information, comparison of group means may disguise heterogeneity within the groups. Indeed, evidence has demonstrated that subgroups with different cognitive profiles exist in PD and in PD-D: the majority of patients have an executive-visuospatial-dominant profile, whereas others have a memory-dominant profile [57, 58]. Similarly, some DLB patients, probably those with more abundant AD-type changes, may lack the characteristic pattern of neuropsychological deficits usually associated with LB diseases.
One of the core characteristics of DLB and PD-D is the high prevalence of neuropsychiatric symptoms (Table 18.2). The profile of neuropsychiatric symptoms is also similar in DLB and PD-D. Persistent VH are the most frequent neuropsychiatric symptom [16, 40, 59-62]. Although misidentification syndromes and delusions are also common and have a similar phenomenology in both DLB and PD-D patients , they may be more prevalent in DLB than in PD-D, possibly due to the morphological and/or neurochemical differences reported in the subsection on Neurochemistry. Depression is also common in both dementias [59-61]. Psychotic symptoms and depression are more frequent in DLB and PD-D than among people with AD, and the characteristic neuropsychiatric profile in DLB is less pronounced in those with more severe AD-type lesions [15, 16]. Apathy, with reduced initiative and motivation, and anxiety are also common neuropsychiatric symptoms. DLB patients more often reported symptoms of anxiety compared with AD patients .