Symptoms, diagnosis, and treatment of low vitamin B12 levels
by Peter Pressman, MD
The term “myelopathy” refers to a disorder of the spinal cord. A myeloneuropathy is a disease process that affects both the spinal cord and peripheral nerves. Symptoms can include an unsteady gait, numbness, weakness, or bowel and bladder problems. The numbness in a myeloneuropathy is usually in a “stocking and glove” distribution beginning in the feet.
The causes of myelopathy are diverse and include autoimmune disorders, tumors, toxins and vitamin deficiencies.
A vitamin B12 deficiency is the most classic form of myeloneuropathy due to a nutritional deficiency.
What is Vitamin B12?
Vitamin B12 is usually found in animal proteins but is common enough in supplemented cereals and some yeast products that it’s uncommon to become deficient as a result of dietary restriction alone. Vitamin B12 is absorbed in a complex manner that relies on a substance called intrinsic factor. This intrinsic factor must be secreted from the stomach and react with the vitamin to allow for proper absorption in the small intestine.
Longstanding vegetarians or vegans who do not take care to supplement may develop a B12 deficiency. But more commonly, the problem results from poor absorption. Some people have an autoimmune disorder in which antibodies attack the cells that secrete intrinsic factor. As a result, B12 cannot be properly absorbed. Gastric bypass surgeries or inflammatory disorders like celiac disease can also lead to vitamin malabsorption.
Medications like metformin and heartburn medications may also lower B12 levels.
Myeloneuropathy from Vitamin B12 deficiency
The myelopathy caused by low vitamin B12 has been called subacute combined degeneration: “subacute” because symptoms develop slowly, “combined” because multiple neurological symptoms are impacted, and “degeneration” because cells can die as a result.
The major part of the spinal cord that is damaged is the posterior columns, which carries information about light touch, vibration, and position sense (proprioception) to the brain. As a result, people feel numbness and may feel tingling as well.
The autonomic nervous system can also be impaired since these fibers also run through the spinal cord. A mild peripheral neuropathy also contributes to these symptoms. In addition, the optic nerve may be compromised (leading to diminished vision) as well as the olfactory bulb (resulting in a decreased sense of smell.) Finally, people can develop dementia which is why this vitamin is routinely checked before diagnosing someone with a disease like Alzheimer’s.
Diagnosis of B12 deficiency
In addition to neurological changes, B12 deficiency can cause a decrease in red blood cells, known as an anemia, and the disorder may be detected when checking a complete blood count.
Vitamin B12 deficiency can be confirmed by a simple blood measurement of the vitamin level. Further studies used in the diagnosis of B12 deficiency include spinal cord magnetic resonance imaging (MRI), somatosensory evoked potentials or visual-evoked potentials. The MRI will show a bright signal in the posterior part of the spinal column.
Evoked potentials show slowing in the visual and sensory pathways. Autonomic testing can confirm orthostatic hypotension due to a dysautonomia.
B12 deficiency can be treated by either oral or intramuscular injections of the vitamin. If possible, the cause of the B12 deficiency should be addressed.
Recovery from Vitamin B12 deficiency
Recovery from B12 deficiency takes time. Typically it requires lifelong supplementation with vitamin B12. Improvement may continue for up to 6 to 12 months of supplementation, though some people will suffer from lasting deficits. Working with a physical or occupational therapist may help people accommodate to any residual problems.
