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Clinical Presentation: A 71-year-old female presented with history of spastic paraparesis. She also complained of leg numbness and weakness for 3 months.

Imaging Findings: There is altered signal within the dorsal cervical spinal cord. Lesions are bilateral symmetrical and near midline in the region of dorsal column. There is no evidence of expansion or swelling of the cord.This area is nonenhancing on the post-contrast images.

Diagnosis: Subacute combined degeneration of the spinal cord

Discussion: Pathologic studies of the spinal cord show multifocal demyelinated and vacuolated lesions in the posterior, lateral, and sometimes anterior columns. Demyelination begins as scattered plaques in the dorsal columns and progresses to the lateral columns. Wallerian degeneration of these tracts may be present. Lesions typically occur in the thoracic and cervical spinal cord but may even affect the medulla [1]. Exactly why demyelination occurs and why specific tracts are more affected than others is uncertain. One theory is that B12 deficiency interferes with all methylation reactions, including those needed for myelin phospholipids. This interference leads to the production of unstable myelin [2].
     The differential diagnosis of an intramedullary lesion is broad and includes demyelinating disorders (multiple sclerosis), infectious causes (HIV vacuolar myelopathy and herpes viruses), inflammatory processes (sarcoidosis), ischemia, and neoplasms (astrocytomas and ependymomas) [3].
     Similar dorsal cord signal changes on MRI have been reported in Sjögren's syndrome [4] and acute autonomic and sensory neuropathy [5] and are believed to result from involvement of the dorsal root ganglion. Spinal cord MRI abnormalities are known to occur in HIV myelopathy, and vitamin B12 deficiency has been felt to play a role in AIDS-associated myelopathy [6]. In contrast to the intramedullary signal change seen due to plaques in multiple sclerosis, the lesions in copper deficiency myelopathy involve long rostral–caudal segments of the midline dorsal cord rather than discrete focal lesions. In general, demyelinating lesions are focal rather than confluent, may show enhancement, are less extensive in their longitudinal extent, and do not have a predilection for the dorsal cord regions. Clioquinol is a copper/zinc-chelating antibiotic that is the etiologic agent in subacute myelo-opticoneuropathy (SMON) [7], and both copper deficiency myelopathy and SMON are characterized by involvement of the dorsal column and corticospinal tracts.

References:

1. Graham DI, Lantos PL. Greenfield's Neuropathology. New York: Oxford Univ. Press, 1997:621-624.
2. Green R, Kinsella L. Current concepts in the diagnosis of cobalalmine deficiency. Neurology. 1995 Aug;45(8):1435-40. [Medline]
3. Tartaglino LM, Flanders AE, Rapoport RJ. Intramedullary causes of myelopathy. Semin Ultrasound CT MR. 1994 Jun;15(3):158-88. [Medline]
4. Sobue G, Yasuda T, Kumazawa K, Yamamoto K, Mitsuma T. MRI demonstrates dorsal column involvement of the spinal cord in Sjögren's syndrome-associated neuropathy. Neurology. 1995 Mar;45(3 Pt 1):592-3. [Medline]
5. Yasuda T, Sobue G, Hirose Y, Mimura M, Yanagi T. MR of acute autonomic and sensory neuropathy. AJNR Am J Neuroradiol. 1994 Jan;15(1):114-5. [Medline]
6. Kieburtz KD, Giang DW, Schiffer RB, Vakil N. Abnormal vitamin B12 metabolism in human immunodeficiency virus infection. Association with neurological dysfunction. Arch Neurol. 1991 Mar;48(3):312-4. [Medline]
7. Konagaya M, Matsumoto A, Takase S, Mizutani T, Sobue G, Konishi T, Hayabara T, Iwashita H, Ujihira T, Miyata K, Matsuoka Y. Clinical analysis of longstanding subacute myelo-optico-neuropathy: sequelae of clioquinol at 32 years after its ban. J Neurol Sci. 2004 Mar 15;218(1-2):85-90. [Medline]