Subacute combined degeneration of the cord (SCD) is caused by a vitamin B12 deficiency.
Most common in patients older than 40 and especially older than 60 7.
The clinical presentation of SCD is usually paresthesia in the hands and feet, with progression to sensory loss, gait ataxia, and distal weakness, especially in the legs.
In the developed world where nutrition is good, it tends to result most commonly from pernicious anaemia. Other possible causes include Crohn disease and other causes of terminal ileitis. Strict vegetarians or those who are undernourished may develop sufficient deficiencies to develop SCD. SCD can be initiated and exacerbated in these groups by nitrous oxide anaesthesia and abusers of nitrous oxide have also been reported to develop SCD 3.
Most commonly there is symmetric bilateral high signal within the dorsal columns. This appearance has been described as the "inverted V sign" 4. The signal changes typically begin in the upper thoracic region, with ascending or descending progression 5. The lateral corticospinal tracts, and sometimes lateral spinothalamic tract may also be involved. Although very unusual, there has been at least one described case of anterior cord involvement 6. Usually these areas have no contrast enhancement. Often there is also accompanying cerebral white matter change. Both spinal and cerebral changes resolve after correction of vitamin B12 deficiency.
Treatment and management
- diagnosis may be confirmed by serum vitamin B12 levels, or holotranscobalamin levels (more sensitive and specific)
- patient may need to be evaluated for pernicious anaemia
- cease nitrous oxide inhalation (if applicable)
- therapy is vitamin B12 replacement
- approximately half will completely recover 7
Clinical differential diagnosis can be broad.
On imaging the differential includes:
copper deficiency myeloneuropathy
- can look identical 8
- infectious causes
- inflammatory processes
- 1. Ravina B, Loevner LA, Bank W. MR findings in subacute combined degeneration of the spinal cord: a case of reversible cervical myelopathy. AJR Am J Roentgenol. 2000;174 (3): 863-5. AJR Am J Roentgenol (full text) - Pubmed citation
- 2. Srikanth SG, Jayakumar PN, Vasudev MK et-al. MRI in subacute combined degeneration of spinal cord: a case report and review of literature. Neurol India. 2002;50 (3): 310-2. Neurol India (link) - Pubmed citation
- 3. Shulman RM, Geraghty TJ, Tadros M. A case of unusual substance abuse causing myeloneuropathy. Spinal Cord. 2007 Apr;45(4):314-7. Epub 2006 Aug 8. Pubmed
- 4. Kumar, Ashok, and Amar Kumar Singh. "Teaching NeuroImage: Inverted V sign in subacute combined degeneration of spinal cord." Neurology 72.1 (2009): e4-e4.
- 5. Ketonen, Leena. Pediatric Brain and Spine: An Atlas of MRI and Spectroscopy. Berlin: Springer, 2005. pg 435, Print.
- 6. Karantanas AH, Markonis A, Bisbiyiannis G. Subacute combined degeneration of the spinal cord with involvement of the anterior columns: a new MRI finding. Neuroradiology. 2000;42 (2): 115-7. Pubmed citation
- 7. Spinal Cord Medicine. Demos Medical Publishing. ISBN:1933864192. Read it at Google Books - Find it at Amazon
- 8. Goodman BP, Chong BW, Patel AC et-al. Copper deficiency myeloneuropathy resembling B12 deficiency: partial resolution of MR imaging findings with copper supplementation. AJNR Am J Neuroradiol. 2006;27 (10): 2112-4. AJNR Am J Neuroradiol (full text) - Pubmed citation