Treatment for Subacute Combined Degeneration of the Cord
The treatment for subacute combined degeneration of the spinal cord is immediate administration of vitamin B12 (hydroxocobalamin) via intramuscular injections, with dosing dependent on the presence of neurological involvement. 1, 2
Diagnosis and Etiology
Subacute combined degeneration (SCD) is a neurological complication of vitamin B12 deficiency characterized by:
- Demyelination of the dorsal and lateral spinal cord 1, 3
- Symptoms including sensory deficits, pyramidal tract symptoms, and postural instability 4
- MRI findings showing symmetrical hyperintense signals in dorsal and lateral columns on T2-weighted images 3, 4
Common causes include:
- Reduced dietary intake (vegetarian/vegan diets) 3
- Nitrous oxide exposure during surgery 3
- Malabsorption (pernicious anemia, autoimmune gastritis) 5
- Previous gastric surgery 4
Treatment Protocol
For Patients with Neurological Involvement:
- Administer hydroxocobalamin 1 mg intramuscularly on alternate days until there is no further improvement 1
- Then continue with hydroxocobalamin 1 mg intramuscularly every 2 months for maintenance 1
- Seek urgent specialist advice from neurologist and hematologist 1
For Patients without Neurological Involvement:
- Administer hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks 1
- Follow with maintenance treatment of 1 mg intramuscularly every 2-3 months lifelong 1
Important Considerations
- Do not delay treatment - Vitamin B12 deficiency allowed to progress for longer than 3 months may produce permanent degenerative lesions of the spinal cord 2
- Do not give folic acid first - It may mask underlying vitamin B12 deficiency and precipitate subacute combined degeneration of the spinal cord 1
- Check vitamin B12 levels before treatment - But be aware that rarely, SCD can occur with normal or even high serum vitamin B12 levels 6
- Oral supplementation is insufficient - Since vitamin B12 deficiency is often caused by malabsorption, parenteral administration is necessary 4
Monitoring and Follow-up
- Monitor hematocrit and reticulocyte counts daily from the fifth to seventh days of therapy and then frequently until the hematocrit is normal 2
- Monitor serum potassium closely during the first 48 hours of treatment and replace if necessary 2
- Follow-up MRI may show resolution of spinal cord abnormalities within three months of treatment 3
Prognosis
- Early diagnosis and treatment can lead to significant improvement or complete resolution of symptoms 3, 4
- Delayed treatment may result in irreversible neurological damage 2
- Most patients show improvement within weeks to months of starting treatment 3, 7
Common Pitfalls to Avoid
- Misdiagnosis - SCD can mimic other myelopathies; MRI is useful for evaluation of the spinal cord 1
- Delayed treatment - Prompt parenteral administration of vitamin B12 prevents progression of neurologic damage 2
- Folic acid administration without B12 - May produce hematologic remission but will not prevent neurologic manifestations 2
- Relying solely on serum B12 levels - In rare cases, SCD can occur with normal or high serum B12 levels due to abnormal binding proteins 6
- Discontinuing treatment - Patients with pernicious anemia require lifelong vitamin B12 injections 2