[Cerebral imaging and depressive disorder]

Cerebral imaging of depressive syndromes has been studied since the early eighties in search of organic or functional anomalies in the central nervous system. There are fewer studies than with schizophrenia. Computed tomography, scintiscan, positron emission tomography (PET) are being used in various depressive states. For methodological reasons, results with PET are only preliminary. EEG mapping, a new technique, has, above all, measured the abnormalities of organic brain syndromes, especially dementia, which has to be ruled out in the diagnosis of depression. CT scan has not substantiated any cerebral defects in depressed patients in the comparative case-control studies, except for some clinical types (aged population or forms associated with delusional or hallucinatory syndromes) where images of cortico-subcortical atrophy have been observed. Scintiscan and PET scan have shown a decreased cerebral blood flow, with a Xenon 133 test, and PET scan a decreased consumption of glucose on condition that depressed subjects are cognitively resting, in comparison to matched controls. In EEG mapping an index of spacetiation of the basal quantitative EEG activity typifies cases of evolution towards dementia, which has to be ruled out in the diagnosis of involutional depression.