subacute combined degeneration
Also written as: SCD — subacute combined degeneration
Spinal cord pathology involving both posterior columns and lateral corticospinal tracts, typically associated with vitamin B12 deficiency.
Full Definition
Subacute combined degeneration is a distinctive pattern of spinal cord pathology characterized by symmetric degeneration affecting both the posterior columns (gracile and cuneate fasciculi) and the lateral corticospinal tracts. The condition most commonly results from vitamin B12 (cobalamin) deficiency, though it can also occur with copper deficiency or nitrous oxide toxicity. Histopathologically, the affected white matter shows spongy degeneration with vacuolation of myelin sheaths, axonal loss, and reactive gliosis. The demyelination typically begins in the posterior columns of the cervical and upper thoracic cord and may progress to involve the lateral and anterior columns. The term 'combined' refers to the involvement of both sensory (posterior column) and motor (corticospinal) pathways. Early changes include myelin swelling and vacuolation, progressing to complete tract degeneration in severe cases. The pathological changes are often accompanied by peripheral neuropathy and may show similar vacuolar changes in the brain, particularly affecting white matter.
Usage
Usage note: Specify anatomical distribution and severity; correlation with B12 levels should be noted when available.
In Context
- "Spinal cord sections demonstrated the classic pattern of subacute combined degeneration with symmetric involvement of posterior columns and corticospinal tracts." — Autopsy report
- "Luxol fast blue staining revealed the characteristic spongy degeneration of white matter consistent with subacute combined degeneration." — Neuropathological examination