Neurochemical Aspects of Dementia Disorders

Dementia disorders are syndromes of cognito-emotional impairment which are disabling and longstanding. Subgroups of dementia are idiopathic dementias or primary degenerative dementias, vascular dementias and secondary dementias. Neurochemical investigations of postmortem human brain material have shown multiple changes in the neurotransmitter metabolism in patients with Alzheimer''s disease (AD) and senile dementia of the Alzheimer type (SDAT). The cholinergic system is severely disturbed, but also the serotonin system and the catecholamines are disturbed. Reduced concentrations of neuropeptides have also been reported in AD/SDAT. It is obvious, however, that in brains from Alzheimer-afflicted patients, there are also disturbances in gangliosides and white matter components. At present, it is not possible to single out one of these changes as of special importance for the dementia disorder. The recorded neurochemical changes in brains from patients with AD/SDAT must, at present, be assumed to be secondary phenomena to a more fundamental disturbance, the nature of which we still do not know. Another explanation may be that the group AD/SDAT is a heterogeneous group, including several from an etiopathological point of view different disorders. In vascular dementia, there seem to be subgroups, and the multi-infarct dementia (MID) is only one of these. In a non-MID vascular group, there are general neurochemical disturbances in the form of reduced activity of cholineacetyl transferase and concentrations of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. Although the neurochemical changes in dementia disorders are looked upon as secondary phenomena, they are of pathogenetic importance. Significant correlations have also been shown between neurotransmitter disturbances and behavioral symptoms. Thus, the neurochemical changes form a basis for formulating treatment strategies.