ERPs and SPECT as early markers of cognitive decline in MCI patients

Objectives: This study aims at evaluating whether functional investigations such as ERPs and SPECT could be considered as early markers of cognitive decline in patients affected by MCI and especially by subjective (SCI), amnestic (aMCI) and multidomain (mMCI) subtypes. Methods: Forty-three patients (age 66.4 ± 7.6; 12 men; MMSE 27.1 ± 2.3; education 10.7 ± 4.1) performed a selective neuropsychological (NP) battery to assess general cognitive status, short- and long-term verbal memory, general intelligence, constructional praxia and verbal fl uency. All patients underwent ERPs recordings (N400 and P300) and 99mTc-HMPAO SPECT. The distribution of MCI subtypes resulted as follows: 8 SCI, 17 aMCI and 18 mMCI. Results: Pathological performances were recorded in the following neurological tests: Rey Auditory Verbal Learning Test (45.0%), FAB (42.9%), Verbal Span (39.5%), Prose Recall (37.2%). The P300 and N400 were altered in 44.0% and 86.0% of the patients tested, respectively. Overall, a signifi cantly higher regional hypoperfusion incidence was detected in all patients with a special interest in the limbic lobe bilaterally, the left frontal lobe (BA6,8,9,10,44,45,46,47) and the left temporal lobe (BA20,22,37). Conclusions: In spite of a normal NP profi le, SCI patients show alterations of ERPs and SPECT patterns compared to other MCIs. Functional exams state the involvement of prefrontal, frontal and temporoparietal areas. The functional networks seem to involve the declarative memory and executive functions: particularly the Working Memory (WM) system seems to be early affected by a possible neuronal dysfunction. The functional impairment is likely to precede detectable structural changes and cognitive defi cit. The use of ERPs and SPECT might be considered as a valuable tool for clinicians to longitudinally screen and monitor subjects with memory disorders, so an early diagnosis of MCI might be able to predict the conversion from MCI to dementia.