Subacute combined degeneration of spinal cord, also known as myelosis funiculus, or funicular myelosis, also Lichtheim's disease, and Putnam-Dana syndrome, refers to degeneration of the posterior and lateral columns of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

as a result of

vitamin B₁₂ deficiency A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrien ...

(most common), vitamin E deficiency, and copper deficiency. It is usually associated with

pernicious anemia Pernicious anemia is a type of vitamin B12 deficiency anemia, a disease in which not enough red blood cells are produced due to the malabsorption of vitamin B12. Malabsorption in pernicious anemia results from the lack or loss of intrinsic fa ...

Signs and symptoms

The onset is gradual and uniform. The pathological findings of subacute combined degeneration consist of patchy losses of

myelin Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...

in the dorsal and lateral columns. Patients present with weakness of the legs, arms, and trunk, and tingling and numbness that progressively worsens. Vision changes and change of mental state may also be present. Bilateral spastic paresis may develop and pressure, vibration and touch sense are diminished. A positive Babinski sign may be seen. Prolonged deficiency of vitamin B₁₂ leads to irreversible nervous system damage. HIV-associated vacuolar myelopathy can present with a similar pattern of dorsal column and

corticospinal tract The corticospinal tract is a white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk. There are more than one million neur ...

demyelination. It has been thought that if someone is deficient in vitamin B₁₂ and

folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...

, the

must be treated first. However, the basis for this has been challenged, although due to ethical considerations it is no longer able to be tested if "neuropathy is made more severe as a result of giving folic acid to vitamin B₁₂- deficient individuals". And that if this were the case, then the mechanism remains unclear. Administration of

nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a ...

anesthesia can precipitate subacute combined degeneration in people with subclinical vitamin B₁₂ deficiency, while chronic nitrous oxide exposure can cause it even in persons with normal B₁₂ levels. Posterior column dysfunction decreases vibratory sensation and proprioception (joint sense). Lateral corticospinal tract dysfunction produces spasticity and dorsal

spinocerebellar tract The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum. Origins of proprioceptive information Proprioceptive information is obtained by Golgi tendon organs and mu ...

dysfunction causes

ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...

Cause

In general, the most common cause of this condition is a deficiency of vitamin B₁₂. This may be due to a dietary deficiency, malabsorption in the terminal ileum, lack of

intrinsic factor Intrinsic factor (IF), cobalamin binding intrinsic factor, also known as gastric intrinsic factor (GIF), is a glycoprotein produced by the parietal cells (in humans) or chief cells (in rodents) of the stomach. It is necessary for the absorption o ...

secreted from gastric parietal cells, or low gastric pH inhibiting attachment of intrinsic factor to ileal receptors. Vitamin E deficiency, which is associated with malabsorption disorders such as

cystic fibrosis Cystic fibrosis (CF) is a rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. O ...

and

Bassen-Kornzweig syndrome Abetalipoproteinemia (also known as: Bassen-Kornzweig syndrome, microsomal triglyceride transfer protein deficiency disease, MTP deficiency, and betalipoprotein deficiency syndrome) is a disorder that interferes with the normal absorption of fat ...

, can cause a similar presentation due to the degeneration of the dorsal columns.

Diagnosis

Serum vitamin B₁₂,

methylmalonic acid Methylmalonic acid (MMA) (conjugate base methylmalonate) is a dicarboxylic acid that is a ''C''-methylated derivative of malonate. The coenzyme A linked form of methylmalonic acid, methylmalonyl-CoA, is converted into succinyl-CoA by methylmalonyl ...

, Schilling test, and a complete blood count, looking for megaloblastic anemia if there is also

folic acid deficiency Folate deficiency, also known as vitamin B9 deficiency, is a low level of folate and derivatives in the body. Signs of folate deficiency are often subtle. A Anemia, low number of red blood cells (anemia) is a late finding in folate deficiency and ...

macrocytic anemia The term ''macrocytic'' is from Greek words meaning "large cell". A macrocytic class of anemia is an ''anemia'' (defined as blood with an insufficient concentration of hemoglobin) in which the red blood cells (erythrocytes) are larger than their no ...

. The Schilling test is no longer available in most areas. MRI-T2 images may reveal increased signal within the white matter of the spinal cord, predominantly in the posterior columns and possibly in the spinothalamic tracts.

Treatment

Therapy with vitamin B₁₂ results in partial to full recovery where SACD has been caused by vitamin B₁₂ deficiency, depending on the duration and extent of

neurodegeneration A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic ...

References

External links

{{Spinal cord lesions Histopathology Neurodegenerative disorders