Folate is an essential vitamin. It was originally isolated from spinach, and was named based on plant "foliage" being the primary natural source of the vitamin. Folate is now available in a variety of different forms, including a synthetic folic acid and the natural active form, 5-methyltetrahydrofolate. Cerebral folate deficiency is a condition that develops when there is inadequate transport of folates into the brain.
Cerebral folate deficiency is a serious medical condition that often develops during the first year of life. The causes are still uncertain, but research indicates that genetic conditions or problems with the immune system may be involved. Natural and synthetic folates are typically absorbed from the diet, but the transport of folate from the blood into the brain is hindered at the choroid plexus, which is the interface of the blood-brain barrier, in people suffering from cerebral folate deficiency. This results in lower levels of active folate in the brain and can lead to a variety of neurodegenerative symptoms. These symptoms may be as benign as irritability or learning difficulties or as severe as seizures and brain damage.
Speculation on the Causes
Cerebral folate deficiency is different from systemic folate deficiency in that the serum or plasma blood levels of folate are normal, but a sample of cerebral spinal fluid indicates decreased levels of folate. The form of folate in the blood and brain is predominately 5-methyltetrahydrofolate (5-MeTHF). This is critical because the concentration of 5-MeTHF in the cerebral spinal fluid is normally three to four times the concentration in plasma.
The genetic causes of this condition are mutations in a folate transporter that actively moves the vitamin from the blood into the brain. These genetic mutations are readily identified by genetic testing, with mutations in the folate receptor being indicated in several cases.
An immune response may also attack the choroid plexus, causing inactivation of this receptor. In such cases, the cause is an autoimmune response that attacks the body, in which autoantibodies bind and cause the immune system to target the choroid plexus and reduce folate transport into the brain.
Research indicates that injections with various forms of folate can help return cerebral folate levels to normal. When the condition is detected and treated early, patients have been reported to improve fully and rapidly. However, detecting low cerebral folate requires an invasive spinal tap to withdraw cerebral spinal fluid for folate measurements. This limits the number of cases that are tested and identified, because severe neurological symptoms must manifest before a spinal tap is performed. It is therefore unclear what portion of the population suffers from mild cases of this condition. Maintaining proper nutrition and vitamin intake is always important for good health, and in one reported case a chewable multivitamin was all that was required to treat this serious medical condition.