Subacute Combined Degeneration of the Cord

Question 1

What causes subacute combined degeneration of the cord?

Answer 1

Vitamin B12 deficiency
Results in impairment of the dorsal columns, lateral corticospinal tracts + spinocerebellar tracts..

Question 2

What lifestyle factor can cause vitamin B12 deficiency and thus subacute combined degeneration of the cord?

Answer 2

Recreational nitrous oxide inhalation

Question 3

How does dorsal column involvement manifest in subacute combined degeneration of the cord?

Answer 3

Distal tingling/ burning/ sensory loss is symmetrical + tends to affect legs more than arms

Impaired proprioception + vibration sense

Question 4

How does lateral corticospinal tract involvement manifest in subacute combined degeneration of the cord?

Answer 4

Muscle weakness, hyperreflexia, + spasticity
UMN signs typically develop in legs first
Brisk knee reflexes
Absent ankle jerks
Extensor plantars

Question 5

How does spinocerebellar tract involvement manifest in subacute combined degeneration of the cord?

Answer 5

Sensory ataxia → gait abnormalities

+ve Romberg’s sign

Question 6

How can subacute combined degeneration of the cord be avoided in patients with macrocytic anaemia?

Answer 6

Always ensure vit B12 levels are checked (+ replenished) BEFORE giving folate