structural:expansion, information:extraction, structural:scholar_edition, quality:corruption
Signs, symptoms and complications

The presence of peripheral sensory-motor symptoms or subacute combined degeneration of the spinal cord strongly suggests the presence of a B deficiency instead of folate deficiency. Methylmalonic acid, if not properly handled by B, remains in the myelin sheath, causing fragility. Dementia and depression have been associated with this deficiency as well, possibly from the under-production of methionine because of the inability to convert homocysteine into this product. Methionine is a necessary cofactor in the production of several neurotransmitters. Each of those symptoms can occur either alone or with others. Vitamin B is essential for the development of the brain. Its deficiency can cause neurodevelopmental problems, which can be partly reversible with early treatment. Only a small subset of dementia cases are reversible with vitamin B therapy. Tinnitus may be associated with vitamin B deficiency.