Subacute Combined Degeneration
of the Spinal Cord
Subacute combined degeneration of the spinal cord is a progressive disorder that is due to vitamin B12 deficiency and produces weakness, clumsiness, tingling, and other abnormal sensations.
This disorder affects about 1 of 10,000 people, usually those who are older than 40. It is due to a deficiency of vitamin B12, which typically also causes pernicious anemia. Usually, the deficiency is not related to diet but to the body's inability to absorb vitamin B12 from the intestine. In this disorder, the columns of sensory nerve fibers in the spinal cord degenerate. The brain, nerves of the eyes, and peripheral nerves are sometimes damaged.
The disorder begins with a general feeling of weakness. Tingling, a pins-and-needles sensation, and numbness are felt in both hands and feet. These sensations tend to be constant and to gradually worsen. People who have this disorder may not be able to feel vibrations and may lose the sense of where their limbs are (position sense). The limbs feel stiff, movements become clumsy, and walking may become difficult. Reflexes may be decreased, increased, or absent. Vision may be reduced.
People who have this disorder may become irritable, apathetic, drowsy, suspicious, and confused. Their emotions may change rapidly and unpredictably. Rarely, dementia develops.
The diagnosis is made based on blood tests to measure levels of vitamin B12 and its breakdown products (metabolites).
Recovery is more likely if the disorder is treated early. When treated within a few weeks after symptoms appear, most people recover completely. If treatment is delayed, the progression of symptoms may be slowed or stopped, but recovery of lost function is unlikely. Injections of vitamin B12 should be given immediately and must be continued indefinitely to prevent symptoms from recurring. For some people, large doses of vitamin B12 taken by mouth are equally effective.
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