EARLY DIAGNOSTIC DIFFERENTIATION BETWEEN PRIMARY DEGENERATIVE DEMENTIA AND PRIMARY DEPRESSIVE SYNDROMES IN THE ELDERLY - A CONTRIBUTION TO PSEUDODEMENTIA DISCUSSION

The syndromes associated with dementia and depression in old age show a considerable overlap and even coincidence, not only for statistical reasons. Starting with a critical evaluation of the term ''pseudodementia'', possibilities for a differentiation of both types of syndromes by characteristics of clinical features and history and by additional investigations are shown. A critical review of the literature with focus on the differentiating properties of the following methods is given: neuropsychology and rating scales (e.g., ''cortical'' mediated versus motivational changes), neurophysiology (electroencephalography, EEG; evoked potentials, EP; event-related potentials, ERP), sleep physiology (REM-sleep changes; sleep deprivation results), neuroendocrinology (dexamethasone suppression test), neuroradiology (cranial computed tomography, CCT; magnetic resonance imaging, MRI) and especially the dynamic imaging methods of nuclear medicine (cerebral glucose metabolism with fluorodesoxyglucose and positron emission tomography, FDG-PET; cerebral blood flow (CBF) measurements with PET and single photon emission tomography, SPET). Developments during recent years concerning better imaging of early hippocampal lesions (MRI) or analysis of CBF - changes induced by activation methods may be very helpful. In conclusion, one can say that the diagnosis of dementia and depression remains primarily a clinical one that can be ascertained by means of valuable diagnostic tools.