Vitamin B12 Levels of Cerebrospinal Fluid in Patients with Organic Mental Disorder

Introduction A wide range of psychiatric symptoms has been associated with pernicious anemia. A number of factors indicate a causal relationship between B12 deficiency and cerebral dysfunction and consequent organic mental change. Deana (1977) demonstrated that vitamin B12 deficiency in the rat has profound effects on several neurotransmitter systems and results in significantly reduced norepinephrine levels in the brain. Uncorrected vitamin B12 deficiency may result in dementia and cerebral lesions similar to spinal cord lesions in subacute combined degeneration of the cord (Mac-Donald, 1956; Roos and Willanger, 1977; Dreyfus and Geel, 1972). In the presence of haematological and/or neurological signs a vitamin B12 deficiency is generally recognized as a contributing if not causative factor for psychiatric symptoms in patients with organic mental disorder. It is less well known that psychiatric symptoms may be the first symptoms of vitamin B12 deficiency and may antedate haematological and neurological symptoms by a long period. Recently Evans (1983) described two such cases, pointing to the importance of serum B12 determinations in patients with organic psychiatric symptoms. However, an intriguing question remains as to what extent B12 in serum is a real reflection of the B12 status of brain tissue. Dreyfus (1970) gave evidence that a low serum B12 status results in low B12 levels in brain tissue. Several authors (Worm-Petersen and Poulsen, 1961; Ukyo, 1971; Taguchi et al., 1977) have suggested the existence of a selective control mechanism for the passage of B12 across the blood-brain-barrier. Ordonez (1977) reviewing the data, speculates that B12 is transferred to the brain at the choroid plexus, which has a very high concentration of B12. Through an active transport mechanism B12 is released to the cerebrospinal fluid (CSF). The protein-B12 complex in the CSF then delivers the B12 to the brain cells. Ordonez states that additional direct uptake by the blood-brain-barrier may be involved. Circumstantial evidence is available indicating that CSF B12 levels can be regarded as indicative for brain tissue B12 status: