Mohammed T. Abou-Saleh

306 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYextended to include areas of cognitive impairment other thanmemory, then it may be considered to be identical to that ofAACD, except for the underlying assumption that it is apotentially pathological, progressive syndrome rather than afeature of normal ageing.To what extent may MCI be considered a prodromal phase ofAD? A number of studies have suggested a significantly elevatedrisk of dementia in MCI subjects, with estimates of 10–15%/yearof MCI subjects developing dementia to 100% over 4 years 8,9,14–17 .These studies are, however, all small hospital-based series. Riskfactors for progression to dementia derived from larger-scalestudies are ApoE 4, higher age, fine motor deficit and lower premorbidIQ 8,12,18 .A number of studies have described neurological changes inCT studies of MCI that distinguish it from normal ageing andsenile dementia 9,14 . The principal characteristic observed in thesestudies is temporal lobe atrophy. Celsis et al. 19 (1997) reportreduced parietal–temporal perfusion and left/right parietal–temporal asymmetry using SPECT in MCI. The observedhypoperfusion levels were found to be intermediate betweenthose found in normal and AD subjects. Julin 20 used alignedSPECT and MRI images to compare MCI with early AD. ADpatients were found to have atrophy and cerebral blood flow(CBF) reduction in both medial temporal and temporoparietalregions, whereas MCI showed significant reduction in CBFwithout atrophy in the temporoparietal region only. Jelic et al. 21have used quantified EEG to demonstrate similarities betweenAD and MCI that differentiate both groups from the normalelderly on temporoparietal coherence and a and y relativepower. These findings suggest that MCI and AD have similaranatomical loci, with MCI being principally differentiated bythe degree of impairment, and functional rather than structuralchange.In a 3 year follow-up study, McKelvey et al. 17 reported that64% of MCI subjects had abnormal SPECT scans at baseline;53% of this cohort developed dementia, but of those developingdementia only 67% had initially abnormal scans, giving a positivepredictive value of only 50%. On the other hand, Johnson et al. 15have demonstrated a clear progression from MCI to dementia,based on SPECT perfusion levels from four regions; thehippocampal–amygdaloid complex, the anterior and posteriorcingulate and the anterior thalamus. The authors conclude that,with semi-quantitative analysis and a spatial resolution sufficientto detect perfusion in limbic structures, it is possible todifferentiate MCI from AD.In conclusion, a number of nosological entities have beenproposed to describe minor cognitive disorders occurring inelderly persons without dementia. MCI will probably evolve asone of the most important concepts in this area, with itsunderlying assumption that cognitive disorders in elderly personsare potential pathologies for which therapeutic care should besought, rather than inevitable features of the normal ageingprocess. The concept appears to be almost identical to that ofAACD, apart from its supposition of underlying pathology, butpresently lacks clear operational criteria for either research orclinical application.REFERENCES1. Kral VA. Senescent forgetfulness: benign and malignant. Can MedAssoc J 1962; 86: 257–60.2. Crook T, Bartus RT, Ferris SH et al. 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