QuestionSBA
QuestionChoice
This would not cause sensory symptoms.
10015677
b
Motor neurone disease
QuestionChoice
This would cause a stamping gait and is usually seen in older patients.
10015679
d
Tabes dorsalis
QuestionChoice
There is no mention of fever, back pain, or risk factors for abscess formation.
10015680
e
Epidural abscess
QuestionChoice
This is a classic combination of symptoms and signs seen in subacute degeneration of the spinal cord, of which nitrous oxide use is a significant risk factor. B12 deficiency can also cause this.
10015676
a
Subacute combined degeneration of the spinal cord
QuestionChoice
The history does not mention multiple presentations over time across different areas of the body.
10015678
c
Multiple sclerosis
QuestionComment
Sounds like your typical Ovidius medic - Adele Hashmino
56269
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Haemophilus Hereditary
QuestionComment
nitrous oxide
59264
User
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Pulseless Electrical Activity
QuestionComment
yo ryan garcia its ye im off the nitrous
60226
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Sydney Sweeney
Concept
Chapter
# Summary

Sub-acute combined degeneration of the cord (SCDC) is a neurological disorder stemming from vitamin B12 deficiency, characterised by the degeneration of the dorsal columns and corticospinal tracts. Key signs and symptoms include symmetrical distal sensory symptoms, diminished vibration sense and proprioception in the legs, and mixed upper and lower motor neuron signs. Investigations primarily involve B12, folate levels, and homocysteine levels, in addition to MRI of the spine and nerve conduction studies. The primary management strategy involves B12 replacement therapy.

# Definition

Sub-acute combined degeneration of the cord (SCDC) is a neurological complication associated with vitamin B12 deficiency. It is characterised by degeneration of both the dorsal columns and corticospinal tracts, whilst preserving pain and temperature sensations. It typically manifests as symmetrical sensory symptoms starting distally and progressing proximally, along with varying degrees of ataxia.

# Aetiology

The underlying cause of SCDC is vitamin B12 deficiency, which can result from various factors including pernicious anemia, malabsorption syndromes, dietary deficiencies, and misuse of nitrous oxide (this causes a **functional** rather than a true B12 deficiency) .

# Signs and Symptoms

- Symmetrical distal sensory symptoms, typically beginning in the feet and progressing to the hands
- Varying degrees of ataxia
- Diminished vibration sense and proprioception in the legs
- Mixed upper and lower motor neuron signs, which may present as exaggerated, diminished, or absent limb reflexes
- Autonomic bladder or bowel symptoms
- SCDC may manifest in both the presence and absence of haematological manifestations.

# Investigations

Diagnostic workup for SCDC should include:

- Assessment of B12 and folate levels
- Homocysteine level analysis; a raised level despite normal B12 could indicate a functional B12 deficiency
- MRI of the spine to exclude cervical myelopathy
- Nerve conduction studies, which will primarily show axonal neuropathy

# Management

The mainstay of treatment for SCDC is:

- Urgent Vitamin B12 replacement, typically using hydroxocobalamin 1 mg IM on alternate days until there is no further improvement, followed by maintenance treatment with hydroxocobalamin 1 mg IM every two months, as per [NICE guidelines](https://cks.nice.org.uk/topics/anaemia-b12-folate-deficiency/).
1978
1976
Subacute combined Degeneration of the Cord
Topic
34
Neurology
15679
Subacute combined degeneration of the spinal cord, characterized by progressive weakness, sensory deficits, and impaired coordination, is commonly associated with vitamin B12 deficiency, which impairs myelin synthesis, and can also result from nitrous oxide use, which inactivates vitamin B12 and disrupts normal neurological function.
An 18-year-old male attends the GP complaining of weakness and tingling of their legs. They have just started university and state they are drinking 40 units of alcohol a week and taking nitrous oxide recreationally. They have no other past medical history. On examination, they have a positive Babinski sign bilaterally with brisk ankle jerks and absent knee jerks. They also have loss of proprioception.

What is the most likely diagnosis?
a