[Early diagnostic differentiation of primary dementia from primary depressive syndromes in the aged--a contribution to the discussion of pseudodementia].

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 fluorodeoxyglucose 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.