Vitamin B12, or cobalamin, is a water-soluble B vitamin. It is important for the proper function of numerous enzymes, especially those involved in DNA metabolism. Low levels of vitamin B12 interfere with cellular functioning, causing many symptoms in the body. The blood cells and nerves are particularly sensitive to B12 deficiency. The nerve damage leads to gait ataxia, which is trouble walking. It is important to consult with a physician for the diagnosis and treatment of health conditions.
Pernicious Anemia
Pernicious anemia is a disease that results in low vitamin B12, leading to anemia and nerve damage with subsequent gait ataxia. In this disease, proteins called antibodies that are supposed to be directed against invading organisms mistakenly target cells in the stomach called parietal cells. Without these cells, the body cannot absorb cobalamin. Over time, the red blood cells can no longer divide properly, leading to low blood counts called anemia. Over time, accumulated nerve damage interferes with stable, coordinated walking.
Nerve Damage
Some of the nerves in the body are surrounded by a sheath called the myelin sheath. The myelin sheath nourishes and protects the cells and speeds up nerve signaling. The lack of B12 damages the myelin sheath. Nerves at the back of the spinal cord, in a part of the cord called the dorsal columns medial lemnisci, or DCML, are particularly sensitive.
Mechanism
The nerves of the DCML normally receive information from the nervous system out in the body, including the feet and legs, and transmit those sensations through the spinal cord, to the brain, where walking is coordinated. Nerve damage to the DCML leads to the inability to perceive the position and movement of the legs, causing gate ataxia -- trouble walking.
Diagnosis and Treatment
A medical history that includes symptoms of anemia, such as fatigue, pale eyes and skin, and nerve problems is consistent with vitamin B12 deficiency and a number of other possibilities. A blood test will reveal low counts of red blood cells, which will also be large in size, called a macrocytic anemia. Blood tests called also measure the levels of vitamin B12, and other chemicals involved in overlapping metabolic pathways, such as folic acid, methylmalonic acid and methionine. The treatment involves the oral or injected administration of vitamin B12, and treating the underlying conditions causing low vitamin B12.
References
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed 2008
- "Neuroscience"; Dale Purves; 4th Ed. 2007
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