Biological markers in dementia

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Abstract
As biopsies are not usually carried out in the diagnosis of dementia disorders, biological markers for dementia must be searched for in the body fluids. Although no changes are found in the concentrations of active amines and minor metabolites of the monoamines in CSF, the major metabolites, homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA), are significantly reduced in patients with Alzheimer's disease (AD) and senile dementia of Alzheimer type (SDAT). The findings from CSF concur with postmortem brain tissue investigations in demented patients. Significant correlations are found between reduced concentrations of monoamine metabolites in CSF and behavioural disturbances as rated by the GBS-scale. Neuroendocrinological studies in dementia show that there is a pathological response to the dexamethasone suppression test in patients with AD, SDAT and multi-infarction dementia (MID). Also, when assessing the postsynaptic NA-sensitivity by giving clonidine, a blunted growth hormone response was recorded. The challenge with the thyrotropin-releasing hormone (TRH) gives a blunted TSH-response in demented patients. It is of interest that there are considerable similarities between neuroendocrinal disturbances in melancholia and in dementia disorders. The investigation of blood is also of value in the diagnosis of dementia disorders. In an investigation of 155 patients admitted to a hospital for suspected dementia it was found that 23% of the patients with late onset primary dementia (SDAT) had low concentrations of vitamin B12, in the blood, high MAO-activity in the platelets and normal concentrations of HVA in CSF.