Vitamin B12 deficiency causes impairment of normal DNA and fatty acid synthesis resulting in megaloblastic anemia, loss of proprioception and vibration sense with sensory disturbance.
MR imaging findings of subacute combined-degeneration of the cord is of long-segment, bilateral T2 hyperintensity of the dorsal columns giving rise to an “inverted V” or “rabbit-ear” appearance. In severe cases, signal abnormality can extend proximally to involve the brainstem and cerebellum.
Causes of B12 deficiency include pernicious anemia, ileal or gastric fundal resection and severely restricted diet.
Copper deficiency, most commonly related to reduced absorption after gastric surgery, can cause an indistinguishable clinical and radiological appearance.
Nitrous oxide administration can provoke symptomatic B12 deficiency in patients with previously subclinical deficiency due to its action in oxidizing active cobalamin into its inactive form.