BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuSubacute combined degenerationSubacute combined degeneration of the spinal cord; SCD Subacute combined degeneration (SCD) is a disorder of the spine, brain, and nerves. It causes weakness, abnormal sensations, mental problems, and vision difficulties.WeaknessWeakness is reduced strength in one or more muscles.Read Article Now Book Mark Article Abnormal sensationsNumbness and tingling are abnormal sensations that can occur anywhere in your body, but they are often felt in your fingers, hands, feet, arms, or le...ImageRead Article Now Book Mark Article Vision difficultiesThere are many types of eye problems and vision disturbances, such as: Halos Blurred vision (the loss of sharpness of vision and the inability to see...ImageRead Article Now Book Mark Article Causes SCD is caused by vitamin B12 deficiency. It mainly affects the spinal cord. But its effects on the brain and the peripheral (body) nerves are the reason for the term "combined." At first, the nerve covering (myelin sheath) is damaged. Later, the entire nerve cell is affected.Doctors do not know exactly how a lack of vitamin B12 damages the nerves. It is possible that the lack of this vitamin causes abnormal fatty acids to form around cells and nerves.People are at high risk for this condition if vitamin B12 cannot be absorbed from their intestine or if they have:Pernicious anemia, a condition in which the body does not have enough healthy red blood cells due to vitamin B12 deficiency Pernicious anemiaAnemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. There are man...ImageRead Article Now Book Mark Article Disorders of the small intestine, including Crohn disease Crohn diseaseCrohn disease is a disease where parts of the digestive tract become inflamed. It most often involves the lower end of the small intestine and the be...ImageRead Article Now Book Mark Article Problems absorbing nutrients, which can occur after gastrointestinal surgery, including weight loss surgery Use of nitrous oxide (laughing gas), especially if used as a recreational drug Symptoms Symptoms include:Abnormal sensations (tingling and numbness) Weakness of the legs, arms, or other areas These symptoms slowly get worse and are usually felt on both sides of the body.As the disease worsens, symptoms may include any of the following:Clumsiness, stiff or awkward movements. ClumsinessUncoordinated movement is due to a muscle control problem that causes an inability to coordinate movements. It leads to a jerky, unsteady, to-and-fr...Read Article Now Book Mark Article Mental changes, which can range from mild memory problems, irritability, apathy, and confusion, to severe dementia and psychosis. Severe dementia is uncommon, but in some cases it's the first symptom of the disorder. DementiaDementia is a loss of brain function that occurs with certain diseases. It affects one or more brain functions such as memory, thinking, language, j...ImageRead Article Now Book Mark Article Decreased vision. Depression. DepressionDepression may be described as feeling sad, blue, unhappy, miserable, or down in the dumps. Most of us feel this way at one time or another for shor...ImageRead Article Now Book Mark Article Sleepiness. Unsteady gait and loss of balance. Unsteady gaitWalking abnormalities can be caused by many different types of problems. Problems with the joints, (such as arthritis), bones (such as deformities),...ImageRead Article Now Book Mark Article Falls due to poor balance. Exams and Tests Your health care provider will perform a physical exam. The exam usually shows muscle weakness and sensation problems on both sides of the body, especially in the legs. Knee jerk reflexes are often decreased or lost. Muscles may have spasticity. There may be reduced senses of touch, pain, and temperature.SpasticitySpasticity is stiff or rigid muscles. It may also be called unusual tightness or increased muscle tone. Reflexes (for example, a knee-jerk reflex) ...ImageRead Article Now Book Mark Article Tests may be needed to determine why you are deficient in vitamin B12.Nerve conduction studies and electromyography may be done to test for nerve damage in the extremities.An eye exam may show damage to the optic nerve, a condition called optic neuropathy. There may also be abnormal pupil responses, loss of sharp vision, and other changes.Optic neuropathyOptic nerve atrophy is damage to the optic nerve. The optic nerve carries images of what the eye sees to the brain.ImageRead Article Now Book Mark Article Blood tests that may be ordered include:Complete blood count (CBC) Complete blood count (CBC)A complete blood count (CBC) test measures the following:The number of white blood cells (WBC count)The number of red blood cells (RBC count)The numb...ImageRead Article Now Book Mark Article Vitamin B12 blood level Vitamin B12 blood levelThe vitamin B12 level is a blood test that measures how much vitamin B12 is in your blood.Read Article Now Book Mark Article Methylmalonic acid and homocysteine blood levelMethylmalonic acid and homocysteine blo...The methylmalonic acid blood test measures the amount of methylmalonic acid in the blood.ImageRead Article Now Book Mark Article Treatment Vitamin B12 is given, usually by injection into a muscle. Injections are often given once a day for a week, then weekly for about 1 month, and then monthly. Vitamin B12 supplements, either by injection or high-dose pills, must continue throughout life to prevent symptoms from returning. Outlook (Prognosis) Early treatment improves the chance of a good outcome.How well a person does depends on how long they had symptoms before receiving treatment. If treatment is received within a few weeks, complete recovery may be expected. If treatment is delayed for longer than 1 or 2 months, full recovery may not be possible.Untreated, SCD results in continued and permanent damage to the nervous system. When to Contact a Medical Professional Contact your provider if abnormal sensations, muscle weakness, or other symptoms of SCD develop. This is particularly important if you or a family member has had pernicious anemia or other risk factors. Prevention Some vegetarian diets, especially vegan, may be low in vitamin B12. Taking a supplement can help prevent SCD.Open ReferencesReferencesPytel P, Anthony DC. Peripheral nerves and skeletal muscles. In: Kumar V, Abbas AK, Aster JC, eds. Robbins and Cotran Pathologic Basis of Disease. 10th ed. Philadelphia, PA: Elsevier; 2021:chap 27.So YT. Deficiency diseases of the nervous system. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 85.AllVideoImagesTogCentral nervous system and peripheral nervous system - illustration The central nervous system comprises the brain and spinal cord. The peripheral nervous system includes nerves outside the brain and spinal cord.Central nervous system and peripheral nervous systemillustrationCentral nervous system - illustration The central nervous system is made up of the brain and spinal cord. The brain functions to receive nerve impulses from the spinal cord and cranial nerves. The spinal cord contains the nerves that carry messages between the brain and the body. Spinal cord injury can occur when there is damage to the cells within the spinal cord or when the tracts of nerves that run up and down the spinal cord are severed.Central nervous systemillustrationCentral nervous system and peripheral nervous system - illustration The central nervous system comprises the brain and spinal cord. The peripheral nervous system includes nerves outside the brain and spinal cord.Central nervous system and peripheral nervous systemillustrationCentral nervous system - illustration The central nervous system is made up of the brain and spinal cord. The brain functions to receive nerve impulses from the spinal cord and cranial nerves. The spinal cord contains the nerves that carry messages between the brain and the body. Spinal cord injury can occur when there is damage to the cells within the spinal cord or when the tracts of nerves that run up and down the spinal cord are severed.Central nervous systemillustrationRelated Information Vitamin B12(Nutrition)Weakness(Symptoms)Numbness and tingling(Symptoms)Vision problems(Symptoms)Pernicious anemia(Condition)Peripheral(Special Topic)Myelin(Special Topic)Crohn disease(Condition)Malabsorption(Condition)Vitamins and Phytonutrients - InDepth(In-Depth)Anemia - InDepth(In-Depth)Crohn disease - InDepth(In-Depth) Review Date: 4/29/2023 Reviewed By: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School of Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. 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Subacute combined degenerationSubacute combined degeneration of the spinal cord; SCD Subacute combined degeneration (SCD) is a disorder of the spine, brain, and nerves. It causes weakness, abnormal sensations, mental problems, and vision difficulties.WeaknessWeakness is reduced strength in one or more muscles.Read Article Now Book Mark Article Abnormal sensationsNumbness and tingling are abnormal sensations that can occur anywhere in your body, but they are often felt in your fingers, hands, feet, arms, or le...ImageRead Article Now Book Mark Article Vision difficultiesThere are many types of eye problems and vision disturbances, such as: Halos Blurred vision (the loss of sharpness of vision and the inability to see...ImageRead Article Now Book Mark Article Causes SCD is caused by vitamin B12 deficiency. It mainly affects the spinal cord. But its effects on the brain and the peripheral (body) nerves are the reason for the term "combined." At first, the nerve covering (myelin sheath) is damaged. Later, the entire nerve cell is affected.Doctors do not know exactly how a lack of vitamin B12 damages the nerves. It is possible that the lack of this vitamin causes abnormal fatty acids to form around cells and nerves.People are at high risk for this condition if vitamin B12 cannot be absorbed from their intestine or if they have:Pernicious anemia, a condition in which the body does not have enough healthy red blood cells due to vitamin B12 deficiency Pernicious anemiaAnemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. There are man...ImageRead Article Now Book Mark Article Disorders of the small intestine, including Crohn disease Crohn diseaseCrohn disease is a disease where parts of the digestive tract become inflamed. It most often involves the lower end of the small intestine and the be...ImageRead Article Now Book Mark Article Problems absorbing nutrients, which can occur after gastrointestinal surgery, including weight loss surgery Use of nitrous oxide (laughing gas), especially if used as a recreational drug Symptoms Symptoms include:Abnormal sensations (tingling and numbness) Weakness of the legs, arms, or other areas These symptoms slowly get worse and are usually felt on both sides of the body.As the disease worsens, symptoms may include any of the following:Clumsiness, stiff or awkward movements. ClumsinessUncoordinated movement is due to a muscle control problem that causes an inability to coordinate movements. It leads to a jerky, unsteady, to-and-fr...Read Article Now Book Mark Article Mental changes, which can range from mild memory problems, irritability, apathy, and confusion, to severe dementia and psychosis. Severe dementia is uncommon, but in some cases it's the first symptom of the disorder. DementiaDementia is a loss of brain function that occurs with certain diseases. It affects one or more brain functions such as memory, thinking, language, j...ImageRead Article Now Book Mark Article Decreased vision. Depression. DepressionDepression may be described as feeling sad, blue, unhappy, miserable, or down in the dumps. Most of us feel this way at one time or another for shor...ImageRead Article Now Book Mark Article Sleepiness. Unsteady gait and loss of balance. Unsteady gaitWalking abnormalities can be caused by many different types of problems. Problems with the joints, (such as arthritis), bones (such as deformities),...ImageRead Article Now Book Mark Article Falls due to poor balance. Exams and Tests Your health care provider will perform a physical exam. The exam usually shows muscle weakness and sensation problems on both sides of the body, especially in the legs. Knee jerk reflexes are often decreased or lost. Muscles may have spasticity. There may be reduced senses of touch, pain, and temperature.SpasticitySpasticity is stiff or rigid muscles. It may also be called unusual tightness or increased muscle tone. Reflexes (for example, a knee-jerk reflex) ...ImageRead Article Now Book Mark Article Tests may be needed to determine why you are deficient in vitamin B12.Nerve conduction studies and electromyography may be done to test for nerve damage in the extremities.An eye exam may show damage to the optic nerve, a condition called optic neuropathy. There may also be abnormal pupil responses, loss of sharp vision, and other changes.Optic neuropathyOptic nerve atrophy is damage to the optic nerve. The optic nerve carries images of what the eye sees to the brain.ImageRead Article Now Book Mark Article Blood tests that may be ordered include:Complete blood count (CBC) Complete blood count (CBC)A complete blood count (CBC) test measures the following:The number of white blood cells (WBC count)The number of red blood cells (RBC count)The numb...ImageRead Article Now Book Mark Article Vitamin B12 blood level Vitamin B12 blood levelThe vitamin B12 level is a blood test that measures how much vitamin B12 is in your blood.Read Article Now Book Mark Article Methylmalonic acid and homocysteine blood levelMethylmalonic acid and homocysteine blo...The methylmalonic acid blood test measures the amount of methylmalonic acid in the blood.ImageRead Article Now Book Mark Article Treatment Vitamin B12 is given, usually by injection into a muscle. Injections are often given once a day for a week, then weekly for about 1 month, and then monthly. Vitamin B12 supplements, either by injection or high-dose pills, must continue throughout life to prevent symptoms from returning. Outlook (Prognosis) Early treatment improves the chance of a good outcome.How well a person does depends on how long they had symptoms before receiving treatment. If treatment is received within a few weeks, complete recovery may be expected. If treatment is delayed for longer than 1 or 2 months, full recovery may not be possible.Untreated, SCD results in continued and permanent damage to the nervous system. When to Contact a Medical Professional Contact your provider if abnormal sensations, muscle weakness, or other symptoms of SCD develop. This is particularly important if you or a family member has had pernicious anemia or other risk factors. Prevention Some vegetarian diets, especially vegan, may be low in vitamin B12. Taking a supplement can help prevent SCD.Open ReferencesReferencesPytel P, Anthony DC. Peripheral nerves and skeletal muscles. In: Kumar V, Abbas AK, Aster JC, eds. Robbins and Cotran Pathologic Basis of Disease. 10th ed. Philadelphia, PA: Elsevier; 2021:chap 27.So YT. Deficiency diseases of the nervous system. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 85.