Diagnosis:
Low B12 level or normal lower limit B12 with high methylmalonic acid
MRI T2: expanded spinal cord, high signal in posterior columns
Pathology:
Shrunken thoracic cord, discoloured posterior & lateral columns
Microscopically: Thoracic cord, bilateral symmetrical white matter vacuolar degeneration “spongy appearance” affecting the long tracts, lipid-laden macrophages, Wallarian degeneration of some axons. Gliosis in late stage.
Myelin stain, neurofilament: axonal spheroids
May affect cerebral white matter & optic tracts.
Treatment:
B12 replacement
Address the cause of the B12 deficiency