Changes in free amino acids of cerebrospinal fluid and plasma in various neurological diseases.

By means of liquid chromatography we investigated free amino acids in cerebrospinal fluid (CSF) (161 subjects) and in plasma (138 subjects) in various neurological diseases and in controls. A general increase in CSF amino acids was found in Group C (samples exhibiting both pleocytosis and increasing CSF protein concentration) and in "spinal canal block" and "neuro-Behçet's syndrome". Also, some abnormalities were detected in these groups with regard to changes in CSF cells, protein or IgG%. In the case of "Guillain-Barré syndrome" we noted an increase in CSF alanine, glycine, methionine, arginine and the branched-chain group. In "multiple sclerosis" an increase was evident in CSF alanine, in plasma alanine and arginine, and in the plasma: CSF ratio of tyrosine. In patients of "motor neuron diseases (MND)" CSF glutamic acid, alanine, histidine and arginine all indicated an increase, along with the plasma: CSF ratio of tyrosine. In Group C and in "neuro-Behçet's syndrome" glycine, methionine and lysine were lowered in the plasma: CSF ratio. Also, the ratio of valine in the former and histidine in the latter indicated a decrease. These results can be supposed to reflect either biochemical abnormalities of plasma and/or the CNS, or changes in the transport systems of the blood-brain barrier.