The blood-brain barrier and folate deficiency.

Twenty-three patients (average age: 63.2 +/- 14.9 (x +/- SEM) ranging from 28 to 83 yr) with low or borderline cerebrospinal fluid (CSF) folate and low serum underwent two lumbar punctures, i.e., before and after 3 wk of folate therapy. The rise in CSF folate content in the whole group after the replacement therapy was significant by both the Lactobacillus casei and radioisotope methods of folate determination. In patients with folate-responsive neurological disorders, the rise of CSF values after replacement therapy was definitely higher than in the group of patients in whom folate deficiency was not related to the actual clinical picture. Contrary to previous statements, the present study revealed that there is not an absolute blood-brain barrier for folate because the lower the CSF folate level was, the more rapid and spectacular the increase in CSF folate after replacement therapy was found.