Subacute combined degeneration

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Central nervous system

Subacute combined degeneration of the spinal cord is a disorder that involves weakness, abnormal sensations, mental problems, and vision difficulties.

Subacute combined degeneration of the spinal cord; SCD

Subacute combined degeneration of the spinal cord is caused by a vitamin B12 deficiency. (For specific information on vitamin B12 deficiency, see the article on pernicious anemia.)

Subacute combined degeneration primarily affects the spinal cord, but it can also damage the brain, the nerves of the eye, and the peripheral (body) nerves. At first, the disease damages the covering of the nerves (the myelin sheath). It later affects the entire nerve cell.

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How a lack of vitamin B12 damages nerves is unclear. However, experts believe the lack of this vitamin causes abnormal fatty acids to form around cells and nerves.

You have a higher risk for this condition if you cannot absorb vitamin B12 from the intestines or if you have:

• Pernicious anemia
• Disorders of the small intestine, including Crohn's disease
• Malabsorptive conditions, which can occur after gastrointestinal surgery

Review Date: 06/25/2009
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).