Subacute combined degeneration of the spinal cord Flashcards
What is subacute combined degeneration of the spinal cord?
What does it effect?
Disorder of the spine, brain and nerves.
Mainly effects posterior and lateral spinal cord causing demyelination.
Can also effect the peripheral nerves hence it is called “combined”
What causes subacute combined degeneration of the spinal cord?
Vitamin B12 deficiency
What is the pathophysiology of subacute combined degeneration of the spinal cord?
What symptoms does this result in?
Demyelination and axonal loss especially in white matter of dorsal column and lateral corticospinal tracts.
Vitamin B12 is a co-factor for 2 enzymes that preserve myelin.
Causing: Paresthesia, sensory ataxia, sensory loss, dementia and muscle weakness.
Who is at risk of getting subacute combined degeneration of the spinal cord?
Pernicious anaemia
Small intestine disorders e.g. Chrons
GI surgery - leading to poor nutrient absorption
Drugs: Nitrous oxide inhalation / metformin / PPI / methotrexate
What tend to be the early symptoms of subacute combined degeneration of the spinal cord?
Paresthesia in extremities
Weakness of legs and arms
As subacute combined degeneration of the spinal cord develops what other symptoms may a patient experience?
Ataxia - unsteady / falls
Sensory loss - clumsiness
Memory problems / confusion / dementia / irritability (neuropsychiatric disturbance)
Decreased vision (optic nerve atrophy)
Sleepiness
What neurological examination findings might you find on a patient with subacute combined degeneration of the spinal cord?
dorsal column involvement:
distal tingling/burning/sensory loss is symmetrical and tends to affect the legs more than the arms
impaired proprioception and vibration sense
lateral corticospinal tract involvement:
muscle weakness, hyperreflexia, and spasticity
upper motor neuron signs typically develop in the legs first
brisk knee reflexes
absent ankle jerks
extensor plantars
spinocerebellar tract involvement:
sensory ataxia → gait abnormalities
positive Romberg’s sign
What tests may you do to confirm nerve damage in the extremities in a patient with suspected subacute combined degeneration of the spinal cord?
Nerve conduction studies and electromyography
What blood tests would be useful in Vitamin B12 deficiency ?
FBC
Peripheral blood smear - megaloblastic anaemia
Serum B12
Reticulocytes (low count)
Vitamin B12 levels can be falsely ‘normal’ in clinic she did below:
Holotranscobalamin (active vitd) will be LOW
Methylamlonic acid- HIGH
Homocysteine- HIGH
(last 2 are markers of vitamin B12 tissue deficiency)
What imaging would you do for subacute combined degeneration of the spinal cord?
MRI of spinal cord
- lesions show as hyperintense often a “V sign” in dorsal columns
What is the treatment for subacute combined degeneration of the spinal cord?
IM hydroxocobalamin injections, followed by oral supplementation.
Avoid using nitrous oxide.
