Subacute combined degeneration of the cord

Subacute combined degeneration of the cord (SCD) is caused by a vitamin B12 deficiency.

Most common in patients older than 40 and especially older than 60 7

The clinical presentation of SCD is usually with loss of vibration and proprioception in the hands and feet, with eventual progression to sensory loss of all modalities, sensory gait ataxia, and distal muscle weakness, especially of the legs. Features of dementia may also become apparent.

SCD can be a sequelae of any cause of vitamin B12 deficiency. In the developed world where nutrition is generally adequate, it tends to result most commonly from pernicious anaemia, but has other causes:

  • Crohn disease and other causes of terminal ileitis (vitamin B12 is primarily absorbed at terminal ileum)
  • use of proton pump inhibitors (acid is required to release vitamin B12 from meat)
  • gastrointestinal surgery (especially if affecting the terminal ileum)
  • coeliac disease
  • atrophic gastritis
  • abuse of nitrous oxide (usually from recreational abuse) 3

Additionally, although uncommon, strict vegetarians or those who are undernourished may develop sufficient deficiencies to develop SCD.

Vitamin B12 levels may be normal in up to 30% of patients, and thus looking for raised levels of other more sensitive and specific biomarkers may be utilised instead:

  • holotranscobalamin
  • methylmalonic acid
  • homocysteine

Most commonly there is symmetric bilateral high signal within the dorsal columns. This appearance has been described as the inverted "V" sign 4. The signal changes typically begin in the upper thoracic region, with ascending or descending progression 5

The lateral corticospinal tracts, and sometimes lateral spinothalamic tract may also be involved. Although very unusual, there has been at least one described case of anterior cord involvement 6. Usually these areas have no contrast enhancement.

Often there is also accompanying cerebral white matter change. Both spinal and cerebral changes resolve after correction of vitamin B12 deficiency.

Management depends on the cause, but generally patients should be provided with intramuscular hydroxocobalamin injections, followed by oral supplementation. Additionally, patients should avoid using nitrous oxide.

Approximately half of all affected patients will completely recover 7.

Clinical differential diagnosis can be broad.

On imaging the differential includes:

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Article information

rID: 2116
Synonyms or Alternate Spellings:
  • Subacute combined degeneration of the cord
  • Sub acute combined degeneration (SCD)
  • Subacute combined degeneration of the spinal cord

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Cases and figures

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    T2 SAG

    Case 1: sagittal T2
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    T2 Axial

    Case 1: axial T2
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    Case 2: sagittal T2
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    Case 2: axial T2
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    Case 7
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    Case 8: with lateral cord involvement
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