Subacute combined degeneration of the cord
4 weeks ataxia and sensory changes.
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High T2 signal is evident posteriorly within the spinal cord, conforming to the dorsal columns. This is most prominent within the cervical cord but is to a lesser extent present in the dorsal columns of the thoracic cord. There is no abnormal enhancement.
Patient was found to be B12 deficient.
Findings are typical of subacute combined degeneration of the cord, in this case related to B12 deficiency.
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.